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Journal of Thermal Analysis and Calorimetry: An International Forum for Thermal Studies (v.111, #3)

Determination of salutary parameters to facilitate bio-energy production from three uncommon biomasses using thermogravimetric analysis by Soumya Sasmal; Vaibhav V. Goud; Kaustubha Mohanty (pp. 1649-1655).
Fuels derived from biomass are renewable as well as environment friendly. In this study, three biomasses viz. husk of areca nut (Areca catheu), trunks of moj (Albizzia lucida), and bon bogori (Ziziphus rugosus) available in North-East region of India were tested as potential biofuel sources. The accentuation of this study was to determine the kinetic parameters using thermogravimetric (TG) technique under air and nitrogen atmosphere. The experiments were carried out within temperature range 300–973 K under air and nitrogen atmosphere at four different heating rates viz. 5, 10, 15, and 20 K min−1, respectively. The mass losses at different lumps in the TG graphs were estimated. The first-order kinetic parameters such as activation energy and pre-exponential factor were calculated for different reaction zones for all the three biomass samples. Effects of atmosphere on combustion characteristics (e.g., peak temperature, ignition temperature, and reactivity index) of biomasses were also determined in this study. Areca nut husk has highest ignition temperature (526.38 K) and reactivity index (0.21) but moj has highest peak temperature (597.91 K) along with highest activation energy (348.04 kJ mol−1) and pre-exponential factor (1.12 × 1024 min−1), respectively.

Keywords: Areca nut husk; Bon bogori; Kinetic parameters; Lignocellulosic biomass; Moj; Thermogravimetric analysis

Exploring antibiotic resistance based on enzyme hydrolysis by microcalorimetry by Le Zhai; Ke-Wu Yang; Cheng-Cheng Liu; Kang-Zhen Xu; Xia Yang; Hui-Zhou Gao; Ying Shi; Lei Feng; Chao Jia; Li-Sheng Zhou; Jian-Min Xiao (pp. 1657-1661).
In an effort to understand the reactions of antibiotics hydrolysis with metallo-β-lactamases (MβLs), the thermokinetic parameters of cefazolin hydrolysis with B1 subclass MβL CcrA from Bacteroides fragilis were determined by microcalorimetric method. The values of activation free energy $$ Updelta G_{ e }^{ heta } $$ are 88.032 ± 0.038, 89.075 ± 0.025, 90.095 ± 0.034, and 91.261 ± 0.044 kJ mol−1 at 293.15, 298.15, 303.15, and 308.15 K, respectively, the activation enthalpy $$ Updelta H_{ e }^{ heta } $$ is 25.278 ± 0.005 kJ mol−1, the activation entropy $$ Updelta S_{ e }^{ heta } $$ is −213.99 ± 0.14 J mol−1 K−1, the apparent activation energy E is 27.776 kJ mol−1, and the reaction order is 1.4. The results indicated that the cefazolin hydrolysis with CcrA is an exothermic and spontaneous reaction. An association between the thermokinetic and kinetic parameters was revealed, which is that the catalytic constant K cat increase with increase in $$ Updelta H_{ e }^{ heta } $$ .

Keywords: Microcalorimetry; Metallo-β-lactamase CcrA; Antibiotic Hydrolysis; Thermokinetic parameters

Exploring antibiotic resistance based on enzyme hydrolysis by microcalorimetry by Cheng-Cheng Liu; Xiang-Bo Zhao; Ke-Wu Yang; Kang-Zhen Xu; Le Zhai; Xia Yang; Hui-Zhou Gao (pp. 1663-1667).
In an effort to explore antibiotic resistance based on enzyme hydrolysis, the thermodynamic parameters of the D-Ala-D-Ala hydrolysis catalyzed by dipeptidase VanX and occurred in Gram-positive vancomycin-resistant pathogens were determined by microcalorimetry. The values of activation free energy $$ Updelta G_{ e }^{ heta } $$ are 87.140 ± 0.055, 88.413 ± 0.067, 89.611 ± 0.051, and 90.823 ± 0.042 kJ mol−1 at 293.15, 298.15, 303.15, and 308.15 K, respectively, activation enthalpy $$ Updelta H_{ e }^{ heta } $$ is 15.332 ± 0.006 kJ mol−1, activation entropy $$ Updelta S_{ e }^{ heta } $$ is −245.02 ± 0.20 J mol−1 K−1, apparent activation energy E is 17.830 kJ mol−1, and the reaction order is 1.5. These thermodynamic data reveal that D-Ala-D-Ala hydrolysis with VanX is an exothermic and spontaneous reaction and has an approximative reaction rate with the imipenem hydrolysis with metallo-β-lactamase ImiS in vitro.

Keywords: D-Ala-D-Ala hydrolysis; Dipeptidase VanX; Microcalorimetry; Thermokinetic parameters

Microcalorimetry coupled with principal component analysis for comparing the effects of two Panax species on mice splenic lymphocytes by Yanling Zhao; Sisi Wei; Jiabo Wang; Ping Zhang; Ruisheng Li; Xiaohe Xiao (pp. 1669-1674).
A powerful microcalorimetric method based on the cell heat production was applied to evaluate the effects of two Panax species on mice splenic lymphocytes growth. Some qualitative and quantitative information, such as the metabolic power-time curves, growth rate constant k, maximum heat-output power P max, appearance time for the highest peak t max, total heat production Q t for all the metabolic progress of mice splenic lymphocytes were obtained to present the effects of Panax ginseng and American Ginseng on these cells. Coupled with principal component analysis (PCA) on these quantitative thermokinetic parameters, the effects of the two Panax species on mice splenic lymphocytes could be quickly evaluated by analyzing the change of the main parameter k. From the values of k, it could be concluded quickly and accurately that Panax ginseng and American Ginseng both showed strong inhibitory effects on mice splenic lymphocytes, and the inhibitory effects was strengthened with increasing concentration of the two Panax species in the concentration range of 0–3.2 mg mL−1. Panax ginseng with IC 50 of 1.38 mg mL−1 showed stronger inhibitory effect on mice splenic lymphocytes growth than American Ginseng with IC 50 of 2.08 mg mL−1. This study indicates that microcalorimetry is a powerful tool for evaluating the drugs’ efficiency on living system, providing some useful references for the application of Panax ginseng and American Ginseng in practice.

Keywords: Microcalorimetry; Panax ginseng ; American Ginseng ; Mice splenic lymphocytes; Inhibitory effect; PCA

Instrumental evidence for biodegradation of tannery waste during vermicomposting process using Eudrilus eugeniae by B. Ravindran; R. Sravani; A. B. Mandal; S. M. Contreras-Ramos; G. Sekaran (pp. 1675-1684).
Animal fleshing (ANFL) is the main solid waste generated during manufacturing leather, which should be disposed friendly to the environment. The effect of epigeic earthworm Eudrilus eugeniae (with and without addition) to transform fermented ANFL in solid state (SSF) and submerged state (SmF) mixed with cow dung and leaf litter into value added product was studied in a vermibioreactor at low residence period (25 days). The products were characterised for pH and C:N ratio and the results were declined at the end of the treatment process with significant reduction in earthworm processed product. The maturity and the chemical changes of the final products were determined using spectroscopic analysis as UV–Visible Spectroscopy in which worm products (vermicompost) reached >5; this indicated that they were well humified. The FT-IR analyses results confirmed the complete mineralisation of polypeptides, polysaccharides, aliphatic methyl groups and lignin, and formation of a deep nitrate band in worm product compared to without worm processed product. Thermogravimetry (TG) and differential scanning calorimetry analyses were carried out in the initial mixture and final products to identify the mass loss and quantitative and qualitative information regarding physical and chemical changes occurred during composting process. The overall results indicated that the maturity of vermicompost (with worms) was in the order SSF > SmF > control. The results indicate that the combination of both fermentation and bacterial/vermicomposting (without worms/with worms) reduced the overall time required for production of well humified organic manure especially with worms.

Keywords: C:N ratio; Eudrilus eugenia ; Fermented ANFL; FT-IR; Thermal analysis; Vermicomposting

Thermogravimetry study of the pyrolytic characteristics and kinetics of macro-algae Macrocystis pyrifera residue by Hui Zhao; Huaxiao Yan; Shuangshuang Dong; Yan Zhang; Binbin Sun; Congwang Zhang; Yanxiang Ai; Biaoqi Chen; Qi Liu; Tongtong Sui; Song Qin (pp. 1685-1690).
Macrocystis pyrifera is one important marine macro-algae, while its residues produced by industrial alginate extraction is a hot potato. To figure out whether its residue is suitable for pyrolysis for biofuel, the pyrolytic characteristics and kinetics of macro-algae M. pyrifera residue was investigated using thermogravimetric method from 50 to 800 °C in an inert argon atmosphere at different heating rates of 5, 10, 20, and 30 °C min−1. The activation energy and pre-exponential factor was calculated by Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose, and Popescu methods, and the kinetic mechanism was deduced by Popescu method. The results showed that the primary devolatilization stage of M. pyrifera residue can be described by Jander function $$ left(left[ {1 - left( {1 - alpha } ight)^{1/3} } ight]^{2} ight) $$ . The average activation energy of M. pyrifera residue was 222.4 kJ mol−1. The results suggested that the experimental results and kinetic parameters provided useful information for the design of pyrolytic processing system using M. pyrifera residue as feedstock.

Keywords: Biomass; Macro-algae; Macrocystis pyrifera ; Residue; Pyrolysis; Kinetics; TG–DTG–DSC

Characterization of herbal medicine with different particle sizes using pyrolysis GC/MS, SEM, and thermal techniques by Lidiane Pinto Correia; José Valdilânio Virgulino Procópio; Cleildo Pereira de Santana; Ana Flávia Oliveira Santos; Horacinna Maria de Medeiros Cavalcante; Rui Oliveira Macêdo (pp. 1691-1698).
Analytical techniques have been used to characterize compounds from herbal medicine, its products and extracts. The objective of this study was to characterize a variety of particle sizes of Erythrina velutina Willd powder. The samples used in the study were named MUF01 (710 μm), MUF03 (180 μm) and MUF05 (75 μm). The techniques employed were scanning electron microscopy (SEM), thermal analysis such as thermogravimetry (TG) and differential thermal analysis (DTA) together with pyrolysis coupled to gas chromatography/mass spectrometry (Pyr-GC/MS). SEM enabled us to detect the existence of divergences from the expected results from the granulometry process. Thermal analytical techniques (TG and DTA) showed the thermal decomposition profile, corresponding to physical and chemical phenomena. The chromatographic data relative to the peak area of the compounds analyzed evidenced quantitative differences in the chemical compositions of the samples MUF01, MUF03, and MUF05 at 300, 450 and 600 °C. Neophytadiene 2,6,10-trimethyl, 14 and 3-eicosyne were identified by Pyr-GC/MS at 300, 450 and 600 °C, and it classified the samples according the peak area values, which were MUF05 > MUF03 > MUF01. SEM, DTA and TG confirmed this through particle size uniformity, heat flow, and mass loss, respectively.

Keywords: Erythrina velutina ; Pyr-GC/MS; Thermal analysis; Scanning electron microscopy

Pyrolysis study of hydrophobic tholins By TG-MS, TG, DTA and DSC methods by José L. de la Fuente; Marta Ruiz-Bermejo; César Menor-Salván; Susana Osuna-Esteban (pp. 1699-1706).
This study presents the thermogravimetry (TG) of hydrophobic tholins, obtained from different simulation experiments of prebiotic synthesis carried out in a CH4/N2/H2 atmosphere with spark discharge activation of aqueous aerosols and liquid water. Differential thermal analysis and differential scanning calorimetry were also used to evaluate the thermal behaviour of these complex organic compounds that could play an important role in prebiotic chemistry. A coupled thermogravimetry-mass spectrometry system allowed us to analyse the principal volatile thermal decomposition and fragmentation products of the hydrophobic tholins under dynamic conditions and an inert atmosphere. During their thermal degradation, which occurs in two stages, a wide variety of hydrocarbon products including methane, vinyl monomers (such as ethylene and propylene), acetylene, oligomers, and some other unknown compounds are found. Besides, a thermally stable structure is present (graphitic structure) in these particular organic substances. Finally, data collected from TG experiments in an oxidative atmosphere showed significant differences at temperatures above 240 °C. According to these results, the different techniques of thermal analysis here applied have proved to be an adequate methodology for the study and characterization of these complex systems, structures of which remain controversial even in these days.

Keywords: Hydrophobic tholins ; Coupled TG-MS; Thermal decomposition; DSC; DTG

Human cytokines characterized by dielectric thermal analysis, thermogravimetry, and differential scanning calorimetry by Salaam Saleh; Druthiman Reddy Mantheni; Manik Pavan Kumar Maheswaram; Susan Moreno-Molek; Tobili Sam-Yellowe; Alan T. Riga (pp. 1707-1716).
Malaria affects over 500 million people worldwide leading to 1–2 million deaths each year, the majority of whom are children. Four Plasmodium species cause malaria in humans. To properly diagnose, and correctly treat malarial infections, accurate diagnosis of infection is required. Proper diagnosis of infection will result in a reduction of morbidity, mortality, and of drug resistant parasites. However, the current tests for malaria diagnosis do not efficiently identify the appropriate human and parasite biomarkers associated with disease. Detection of specific inflammatory mediators such as cytokines associated with malaria pathogenesis will aid the determination of disease progression, disease prognosis, and the early diagnosis of malaria infection. In this study, we used dielectric thermal analysis (DETA), thermogravimetric analysis, and differential scanning calorimetry (DSC) to characterize five human cytokines (IL-1α, IL-2, IL-4, IL-6, and IL-10), to demonstrate how their thermoanalytical properties can be investigated for sensor design. Analysis for DETA was performed at a frequency range of 0.1–300,000 Hz. Permittivity and loss factor measurements were used to calculate tan δ values. Peak frequencies were used to determine dielectric signatures for each cytokine. The peak frequencies were different for each cytokine analyzed. In addition, activation energies were frequency dependent for IL-2 but frequency independent for the remaining four cytokines. Cytokines were also examined using DSC which established variance in heat of crystallization and heat of fusion of solvent among the five cytokines. A noticeable differentiation was observed with IL-1α among the other four cytokines when analyzed using trend analysis. Detection of unique dielectric signals will aid development of sensitive dielectric sensors capable of detecting cytokines in various human samples.

Keywords: DETA; TG; DSC; Cytokines; Malaria; Plasmodium falciparum

Thermal and dynamic behaviour of the actin monomer in case of different cations by F. Könczöl; J. Belagyi; D. Lőrinczy (pp. 1717-1723).
Actin is one of the important elements of the striated muscle that transmits force from the myosin filaments and as a part of the cytoskeleton plays an important role in shape determination of cells. It is a known experience that removal of the divalent cation affects the dynamic behaviour of actin in both forms. Paramagnetic probes and electron paramagnetic resonance (EPR) spectroscopy provide direct technique by which the rotation and the orientation of specifically labelled proteins can be followed during biochemical manipulations. The spectroscopic measurements could be combined with DSC measurements that report domain stability and interactions and allow the calculation of the thermodynamic parameters during the melting process. Actin was spin-labelled with maleimide or fluoro-dinitro proxyl probe molecules which are bound to the Cys-374 or Lys-61 residues of the smaller domain. EPR spectroscopy spectra were recorded in monomer form in Ca- and EGTA-state as a function of temperature up to the melting point. Similarly, DSC measurements were performed and analyzed using the kinetic theory. The measurements showed that removal of the divalent cation from the globular actin induced significant local and global structural change both in the thermodynamic properties and the rotational mobility of actin detected by DSC and EPR. On the basis of the results derived by deconvolution of the DSC pattern we can suggest a non-interactive two-domain melting for the monomer actin after removing the divalent cations.

Keywords: Actin; Divalent cations; ATP; Spin-labelling; EPR; DSC

Thermal study on complexes with Schiff base derived from 1,2,4-triazole as potential antimicrobial agents by Larisa Calu; Mihaela Badea; Denisa Falcescu; Daria Duca; Dana Marinescu; Rodica Olar (pp. 1725-1730).
In order to develop new metallo-antimicrobials the complexes of type MLCl·nH2O ((1) M: Co, n = 0; (2) M: Ni, n = 2; (3) M: Cu, n = 2.5; (4) M: Zn, n = 0, HL: Schiff base derived from acetylacetone and 3-amino-4H-1,2,4-triazole) were synthesized by template condensation. The features of complexes have been assigned from microanalytical, IR and UV–Vis-NIR data. The species heating in air evidenced processes as melting, water and hydrochloride endothermic elimination as well as oxidative degradation of the Schiff base. The temperature ranges as well as modification in the electronic spectra of dehydrated intermediates indicate the presence of both coordination and crystallisation water molecules. The final product of decomposition was the most stable metal oxide as powder X-ray diffraction indicated.

Keywords: Acetylacetone; Complex; Schiff base; 1,2,4-Triazole; Thermal behaviour

Microcalorimetry study on the microbial activity of permafrost on the Tibetan plateau of China by Bingjing Ye; Huyuan Feng; Jihua Zhao; Jian Fang; Weiguo Shen (pp. 1731-1736).
Microcalorimetric techniques had been used to study the influence of different physicochemical parameters on microbial growth in different permafrosts on the Tibetan plateau. The total heat evolution of the permafrost samples amended with glucose, Q T , the values of microbial growth rate constant, k, and the heat output power, P t , were calculated from the power–time (Pt) curves. It is observed that the same coverage vegetation show similar Pt curves, which strongly suggest that the permafrost microorganisms of the homology vegetation coverage have similar structures of community. Furthermore, the vegetation degradation turns out to have significant influence, that is, the better the status of vegetation is, the higher the values of k, CFU and Q T are.

Keywords: Microcalorimetry; Tibetan plateau; Permafrost; Vegetation; Microbial activity

Macromolecular interactions of spectinomycin with Bovine serum albumin by Mahmoud Kandeel; Mohamed Nabih; Yukio Kitade (pp. 1737-1741).
Among the pharmacokinetic parameters of chemotherapeutics, serum albumin binding is a critical factor in determining drug distribution and bioavailability. In this study, the binding properties as well as the interaction of spectinomycin with Bovine serum albumin was investigated. Spectinomycin showed stronger binding with BSA at higher temperatures, which diminishes by decreasing the temperature. The binding constant of spectinomycin with BSA varied from 3.1 × 103 M−1 at 298 K to 6.3 × 103 M−1 at 313 K. By increasing the temperature, from 298 to 313 K, the binding affinity was increased by twofolds. Thermodynamic analysis indicated changes in albumin conformation and partial loss of folding during spectinomycin-albumin binding. The mild-moderate binding affinity of spectinomycin with BSA will be important in determining the drug–drug interactions at the binding sites of BSA. The presence of stronger binding ligand e.g., chloramphenicol, tetracyclines or diclofenac will compete with spectinomycin for its binding sites, therefore, lowering its serum albumin binding. The result of this study will be helpful in understanding of the binding properties and mechanisms of interaction of spectinomycin with bovine serum albumin.

Keywords: Spectinomycin; BSA; Binding; ITC

Synthesis, spectral and thermal study on new Fe(III) complexes with N,N-dimethylbiguanide as antibacterial agents by Mihaela Badea; Ana-Maria Crasanda; Mariana Carmen Chifiriuc; Luminita Marutescu; Veronica Lazar; Dana Marinescu; Rodica Olar (pp. 1743-1751).
New complexes [FeO(DMBG)]2 and [Fe(DMBG)2]Cl·0.5H2O (HDMBG: N,N-dimethylbiguanide) have been synthesized and characterized by microanalytical, IR and UV–Vis data. Electronic spectra of the complexes are characteristic for a tetrahedral stereochemistry, whilst the modifications in the IR spectra indicate the presence of the DMBG anion as chelate. The thermal decomposition investigated in air by thermal analysis confirmed the proposed formulas for the complexes and provided information concerning the modifications during heating and also the thermodynamic effects accompanying them. The thermal transformations are complex, according to TG and DTG curves including dehydration, hydrochloric acid elimination, oxidative degradation and condensation of –C=N– unit. The final product of decomposition was iron (III) oxide as powder XRD indicates. Complexes were screened for their antimicrobial properties against Gram-positive, Gram-negative bacterial, as well as fungal pathogenic strains. The results indicate that Fe(III) complexes exhibit an improved antibacterial activity against S. aureus and E. coli strains in comparison with free biguanide. The Fe(III) complexes also inhibit the ability of S. aureus, B. subtilis, P. aeruginosa and E. coli strains to colonize the inert substratum, accounting for their possible use as anti-biofilm agents.

Keywords: Antimicrobial activity; Iron(III) complex; 1,4-Diazino-polycondensed species; N,N-Dimethylbiguanide; Thermal behaviour

Thermal, spectral, electrochemical and biologic characterization of new Pd(II) complexes with ligands bearing biguanide moieties by Mihaela Badea; Elica Iosub; Carmen Mariana Chifiriuc; Luminita Marutescu; Emilia Elena Iorgulescu; Veronica Lazar; Dana Marinescu; Coralia Bleotu; Rodica Olar (pp. 1753-1761).
New complexes [Pd(HDMBG)2]Cl2·H2O, [PdL1]Cl2·0.5H2O and [PdL2]Cl2·1.5H2O (HDMBG: dimethylbiguanide, L1 and L2: ligands resulted from HDMBG, ammonia/hydrazine and formaldehyde template condensation) were synthesized and characterized. The features of complexes have been assigned from microanalytical, IR, UV–Vis and cyclic voltammetry data. The thermal transformations are complex processes according to TG and DTA curves including water and hydrochloric acid elimination, thermolysis processes leading to paracyanide formation as well as PdO decomposition, final product being palladium. Complexes were screened for their antimicrobial properties against some pathogenic Gram-positive and Gram-negative bacterial as well as fungal Candida albicans strains. The complexes exhibit specific antibacterial and/or antifungal activity, depending on their structure and the tested microbial strains. All complexes inhibit the microbial biofilm development on the inert substratum. It was also observed that PdCl2 complexation minimized their cytotoxic effect on the eukaryotic cells.

Keywords: Biguanide; Biofilm; One-pot condensation; Palladium(II) complex; Thermal behaviour

Synthesis, characterization, and thermal decomposition of new copper (II) complex compounds with chlorhexidine by Mihaela Badea; Rodica Olar; Monica Iliş; Rodica Georgescu; Mirela Călinescu (pp. 1763-1770).
Three new copper (II) complex compounds with chlorhexidine (CHX) as ligand have been prepared and characterized by elemental and thermogravimetrical analyses, molar conductances, infrared, and UV–Vis spectra. Chlorhexidine acts as neutral tetradentate NNNN donor, coordinating through the four imine nitrogen atoms. Based on the experimental data the following formulas have been proposed for the complex compounds: [Cu(CHX)](NO3)2 (1), [Cu2(CHX)Br2Cl2]·4H2O (2), and [Cu(CHX)Cl]Cl (3). Thermal decomposition evidenced dehydration (complex 2), anionic moieties release and the ligand cleavage with chlorobenzene moieties removal for all complexes. The final residue is in all cases copper oxide. Antibacterial and antifungal activities of the complexes have been determined in vitro, by the cup-plate agar diffusion method, against Escherichia coli, Staphyloccocus aureus, and Candida albicans. The complexes present an activity comparable to that of chlorhexidine, the most active being [Cu2(CHX)Br2Cl2]·4H2O.

Keywords: Antimicrobial activity; Biguanide; Chlorhexidine; Copper (II) complex

Thermal decomposition study and biological characterization of zinc(II) 2-chlorobenzoate complexes with bioactive ligands by Lenka Findoráková; Katarína Győryová; Daniela Hudecová; Dagmar Mudroňová; Jana Kovářová; Katarína Homzová; Faten A. Nour El-Dien (pp. 1771-1781).
New zinc(II) 2-chlorobenzoates of general formula [Zn(2-ClC6H4COO)2(L)2] (where L = caffeine—caf, urea—u, methyl-3-pyridylcarbamate—mpc, phenazone—phen, theophylline—thp) were synthesised and characterised by elemental analysis and IR spectroscopy. The thermal behaviour of the complexes was studied by TG/DTG and DTA methods in nitrogen and in air atmosphere. During the thermal decomposition of the studied compounds the release of organic ligands take place followed by the decomposition of 2-chlorobenzoate anion. The volatile decomposition intermediates were proved by mass spectrometry. Zinc oxide was found as the final product of the thermal decomposition performed up to 1,000 K. The antimicrobial activity of the zinc(II) complexes against various strains of bacteria, yeasts and filamentous fungi has been investigated. It was found that the prepared compounds decreased the growth of Staphylococcus aureus, Escherichia coli, Candida albicans, Rhizopus oryzae and Microsporum gypseum, respectively. The most resistant to all tested compounds was probiotic strain of Lactobacillus plantarum. The presence of zinc and ligands in the prepared compounds increased the inhibitory effect compared to sodium salt of prepared compounds and free ligands.

Keywords: Zinc; 2-Chlorobenzoate; Thermal; Spectral properties; Bioactive ligands

Thermal study of new biologic active complexes with mixed ligands by Gina Vasile; Rodica Olar; Dana Marinescu; Angela Kriza; Luminita Marutescu; Mariana Carmen Chifiriuc; Veronica Lazar; Mihaela Badea (pp. 1783-1790).
Five new coordinative compounds that contain mixed ligands (4,4′-bipyridine and methacrylate anion) were synthesized and characterized (elemental analysis, IR and UV–Vis spectroscopy, and thermal studies). The complexes are of the type [M(4,4′-bipy)(C4H5O2)2nH2O ((1) M:Mn, n = 0; (2) Co, n = 0.5; (3) M:Ni, n = 1.5; (4) M:Cu, n = 0.5; (5) M:Zn, n = 0.5; 4,4′-bipy: 4,4′-bipyridine; C4H5O2: methacrylate anion). All the tested complexes exhibited very low MIC values against Escherichia coli strains and one compound against Staphylococcus aureus. Besides the specific antimicrobial spectrum, these compounds also inhibited the microbial ability to colonize the inert surfaces, acting as potential anti-adherence and biofilm-controlling agents. The thermal behavior provided confirmation of the complexes' compositions as well as the number and the nature of water molecules and the intervals of thermal stability.

Keywords: Antimicrobial activity; 4,4′-bipyridine; Complex; Methacrylate; Thermal behavior

Experimental study and performance evaluation of various cook stove models based on energy and exergy analysis by S. K. Tyagi; A. K. Pandey; S. Sahu; V. Bajala; J. P. S. Rajput (pp. 1791-1799).
This article presents the experimental study and comparative performance evaluation of four types of cook stoves using energy and exergy analysis. Analysis of four different types of cook stove models viz. Envirofit, Mangla, Harsha and Vikram were selected and the water boiling test has been carried out. The suitable biomass available from the local market was prepared in the proper size as described in the Bureau of Indian Standards (BIS) and has been used as the fuel for cook stove in this experimental study. The aluminium pots of proper capacity as per BIS standard have been used for different cook stoves. The data from the experiments was collected and evaluated for the energy and exergy efficiencies for different models. Based on the data analysis it is found that the exergy efficiency is much lower than that of the energy efficiency for all the four models. It is also found that the both the efficiencies of Envirofit model are found to be higher than those of other models studied here.

Keywords: Improved cook stove; Exergy and energy analysis; Thermal efficiency; Water boiling test; Burning capacity rate; Calorific value

Differential scanning calorimetry (DSC) analysis of human plasma in different psoriasis stages by Moezzi Mehdi; Tamás Fekecs; István Zapf; Andrea Ferencz; Dénes Lőrinczy (pp. 1801-1804).
Psoriasis vulgaris is a chronic autoimmune, inflammatory and proliferative skin disease. Recently, there is a need for new methods to detect and to monitor this dermatological syndrome at any stage. The application of differential scanning calorimetry (DSC) should be as a new diagnostic method for psoriasis detection and monitoring using human plasma. We aimed to detect blood plasma components with DSC in psoriasis patients. The study included 18 white adults (eight men and ten women; median age 55.7 years) who had underwent a full skin examination for psoriasis. According to the psoriasis area severity index (PASI) we selected them into three groups: PASI: 0 (symptomless), PASI: 1–6 (minimal symptoms), PASI: >7 (symptoms). According to medical treatment human blood plasma samples were collected from healthy controls, patients without or with therapy, and were analyzed by DSC technique. In this preliminary study we observed that thermal changes (T m, calorimetric enthalpy) in blood plasma showed closed correlation with psoriasis severity and medical treatment. Further studies are needed to elucidate these relationships, but our application of the DSC method has provided a potential new tool for the early diagnosis and monitoring of psoriasis patients.

Keywords: DSC; Psoriasis vulgaris; PASI score

Agar-based heat-sensitive gel with linear thermal response over 65–80 °C by Arsalan K. Siddiqi; Sang Hyun Cho (pp. 1805-1809).
A nontoxic heat-sensitive gel containing 1.5 % (w/v) agar and 25 % (w/v) bovine serum albumin (BSA) was fabricated in this study. Optical density measurements with 808 nm near-infrared (NIR) laser indicated that, in spite of its BSA content, the current agar + BSA gel remained similar to agar only gel in terms of its optical response to NIR laser. The thermal response of the current agar + BSA gel to high temperatures was quantified using magnetic resonance imaging (MRI). According to the MRI measurements of T2 relaxation rate as a function of heating temperature, the current agar + BSA gel showed a linear response to heating temperatures between 65 and 80 °C, while it remained thermally stable at temperatures up to 80 °C. Therefore, the current agar + BSA gel can be used as thermal dosimeters or volumetric heat-sensitive gel phantoms in typical thermal therapy regime.

Keywords: Heat-sensitive gel; Bovine serum albumin; Magnetic resonance imaging

A biomass pyrolysis model for CFD application by Ion V. Ion; Florin Popescu; Gina G. Rolea (pp. 1811-1815).
The CFD modeling of biomass combustion or gasification systems needs a description of the volatiles composition that is formed during devolatilization and char oxidation processes. The present model can be used as a submodel in the CFD modeling of combustion or gasification process. This study is a combination of relevant models and data available in the literature to formulate a model that predicts the volatiles in terms of a few simple species. The volatile species considered by this model are CO, CO2, H2O, H2, light hydrocarbons, and heavy hydrocarbons. The model predicts the volatiles as a function of temperature for different biomasses. The model was applied for pyrolysis of briquettes made from agricultural residues. The results are in good agreement with data from literature.

Keywords: Volatiles; Modeling; Agricultural residues; Pyrolysis; Temperature

Determination of ligand to DNA binding parameters from two-dimensional DSC curves by E. V. Dukhopelnikov; E. G. Bereznyak; A. S. Khrebtova; A. O. Lantushenko; A. V. Zinchenko (pp. 1817-1827).
The application of the theory of DNA denaturation linked to ligand binding to differential scanning calorimetry (DSC) is a useful tool to simultaneously characterize the energetics of denaturation and binding. Although the general theory is well known, the current DSC-based approaches to study the DNA–ligand interaction do not utilize the full potential of this method. In this paper, we propose the analytical approach for detailed analysis of DNA–ligand interaction from DSC data. The DNA macromolecule is represented as an assembly of cooperative units which melt by two-state model. The explicit account of ligand distribution on polymeric DNA and the temperature dependences of melting and binding constants, as well as of enthalpies, are considered. Such approach enables to extract the binding constant, stoichiometry, enthalpy, entropy, and heat capacity changes from multiple excess heat capacity profiles obtained at varying concentrations of the ligand (i.e. two-dimensional DSC curves). The applicability of the developed approach was demonstrated using an example salmon testes DNA–proflavine DSC experiment. The full set of DNA melting and proflavine binding thermodynamic parameters was obtained. Comparison of the proflavine binding parameters obtained from DSC with those determined from alternative experimental methods has proved the usefulness of the DSC method for evaluation of the binding thermodynamics in DNA–ligand system. In addition, the approach developed in the present study, allows to evaluate the concentration dependences of all species in solution as a function of temperature. Analysis of these dependences has enabled to interpret fine effects on the DSC curves of DNA–ligand complexes.

Keywords: DSC; DNA; Ligand; Thermodynamics; Binding parameters; Proflavine

Investigation of metal–buffer interactions using isothermal titration calorimetry by D. Wyrzykowski; B. Pilarski; D. Jacewicz; L. Chmurzyński (pp. 1829-1836).
Isothermal titration calorimetry (ITC) and potentiometric titration (PT) methods were used to study the interactions of cobalt(II) and nickel(II) ions with buffer substances 2-(N-morpholino)ethanesulfonic acid (Mes), dimethylarsenic acid (Caco), and piperazine-N,N′-bis(2-ethanesulfonic acid) (Pipes). Based on the results of PT data, the stability constants were calculated for the metal–buffer complexes (T = 298.15 K, ionic strength I = 100 mM NaClO4). Furthermore, calorimetric measurements (ITC) were run in 100 mM Mes, Caco, and Pipes solutions with pH 6, at 298.15 K. The enthalpies (ΔH) of the metal–buffer complexation reactions were calculated indirectly by displacement titration using nitrilotriacetic acid (H3NTA) as a strong-binding, competitive ligand. Finally, to verify obtained results, the number of protons released by H3NTA due to complexation of the cobalt(II) and nickel(II) ions was determined from calorimetric data and compared with results of calculations.

Keywords: Isothermal titration calorimetry; Metal–buffer interactions; Potentiometric titration; Proton exchange; Thermodynamic parameters

Microcalorimetric determination of the activity of supercritical extracts of wormwood (Artemisia absinthium L.) over Spodoptera littoralis by Luis Martín; Azucena González-Coloma; Jesús Burillo; Antonio M. F. Palavra; José S. Urieta; Ana M. Mainar (pp. 1837-1844).
The aim of this study is to develop a method and to determine by means of isothermal microcalorimetry the activity of supercritical extracts obtained from growth-controlled wormwood (Artemisia absinthium L.) over Spodoptera littoralis L. (S. littoralis), a polyphagous pest of the Mediterranean crops. In order to achieve this goal, a three-step microcalorimetric method has been developed to insure the quality of the measurements and the validity of the results. Once optimized, different extracts of wormwood obtained by means of supercritical fluid extraction and by traditional methods have been used to investigate their effects over S. littoralis. The microcalorimetric method serves as a tool to complement other bioassays found in the literature. Several extracts from supercritical extractions with solvent density ranging from 485.5 to 819.5 kg m−3 have been tested. The influence of an entrainer addition to the supercritical fluid has also been investigated. The traditional extracts were obtained by hydrodistillation and organic Soxhlet extraction. The supercritical extracts were more efficient against S. littoralis than the traditionally obtained extracts.

Keywords: Microcalorimetry; Supercritical fluid extraction; Bioactivity; Wormwood (Artemisia absinthium L.); Spodoptera littoralis ; Traditional extraction methods

Effects of low-dose ionizing radiation on α,β-globulins solutions studied by DSC by Anna Michnik; Kinga Polaczek-Grelik; Piotr Leśniak; Zofia Drzazga (pp. 1845-1852).
An attempt has been made to detect the effect of a small dose of ionizing radiation on the course of α,β-globulin thermal denaturation in aqueous solutions. Doses of 0.1 and 1.8 Gy have been delivered using γ-rays emitted by 60Co isotope while doses of 10 and 100 Gy have been supplied by X-rays produced by linear accelerator. The highest dose has visibly changed DSC curve of protein solution while the changes due to lower doses are hardly detectable. Although very weak, the irradiation effect found has been dose dependent. The results suggest that the influence of ionizing radiation on globulins solution is bigger when the dose rate is lower at given dose. The opposite direction of differences between irradiated and control samples for fresh and stored protein solutions suggests various characters of changes in initial and later period of sample aging. This may be an important reason for difficulties in an investigation of the effect of ionizing radiation on protein solution, especially for low doses delivered very slowly.

Keywords: α,β-Globulins; Differential scanning calorimetry; Gamma and X-irradiation; Protein denaturation; Protein aging

Application of thermovision for estimation of the optimal and safe parameters of the whole body cryotherapy by Agnieszka Dębiec-Bąk; Anna Skrzek; Halina Podbielska (pp. 1853-1859).
Exposure to the extreme low temperatures, ranging between −60 and −140 °C, has many beneficial effects on the human body what is exploited for example in sport medicine, for treatment of locomotory system diseases or even some psychiatric disorders. To insure the safe treatment in a cryochamber, careful planning of the procedure and proper qualification of patients, is required. Cardiovascular system, especially skin vasculature plays the major role of the body response to the extreme cold. The changes in skin blood flow are reflected in changes of the temperature distribution. Therefore, the thermal imaging, which allows to analyze the temperature distribution on the human body, may be successfully exploited to examine the influence of extremely low temperatures on the skin vascular system. The aim of this work was to examine the temperature, blood pressure, and heart rate changes after the whole body cryotherapy in healthy subjects to determine the safety conditions of the treatment. 480 healthy students of the Wrocław University School of Physical Education were divided into two groups (each 240 persons). All subjects were exposed for 1–3 min to the extremely low temperatures: −60, −100, −120, and −140 °C. In one group, the thermograms were recorded before and 5 and 30 min after the cryotherapy by means of ThermoVision A20 M thermal camera. In the other one, heart rate and blood pressure were measured before and 5 min after the cryotherapy. It was demonstrated that 3-min exposure in the cryochamber and the temperature −120 °C are the optimal and safe cryotherapy parameters.

Keywords: Whole body cryotherapy; Blood pressure; Heart rate; Thermovision

Anaerobic digestion of municipal solid waste and sewage sludge under mesophilic and thermophilic conditions by Maria Rosaria Provenzano; A. Daniela Malerba; Alessandro Buscaroli; Denis Zannoni; Nicola Senesi (pp. 1861-1870).
In this study, thermal analysis in differential scanning calorimetry associated to Fourier self-deconvolution (FSD) of infrared spectra was applied to the study of anaerobic digestion of the organic fraction of domestic solid waste and sewage sludge mixed in 1:1 ratio under mesophilic and thermophilic conditions. Curves showed an exothermic peak in the high-temperature range and a number of endothermic and/or exothermic peaks in the low- and medium-temperature range. The high-temperature exotherm was a common feature on curves of all samples. Digestates evidenced a shift of this exotherm toward higher temperature with respect to both substrates and feed-in materials as a result of a greater chemical complexity attained by organic matter (OM) during the process. A further shift toward higher temperature values was observed on digestates obtained under thermophilic conditions with respect to digestates obtained under mesophilic conditions. This result was associated to a higher recalcitrance of digestates produced under more drastic conditions. Based on evidence obtained by FSD spectra, the exotherm in the medium-temperature range was assigned to combustion of carbohydrates and to loss of aliphatic structures and carboxylic groups. Enthalpy data associated to the high-temperature exotherm were used to differentiate feed-in materials and their corresponding digestates and to distinguish digestates obtained under different operative conditions.

Keywords: Anaerobic digestion; Thermal analysis; Fresh substrates; Digestates

DSC and Raman study on the effect of lysozyme and bovine serum albumin on phospholipids liposomes by M. Di Foggia; S. Bonora; V. Tugnoli (pp. 1871-1880).
In this paper, the effect of increasing amounts of lysozyme (Lyso) and bovine serum albumin (BSA) on the behaviour of lecithin (DMPC) and cephalin (DMPE) liposomes was investigated by means of Raman and DSC techniques. The results showed that both proteins affected, but in a different way, both lecithin and cephalin liposomes. In the samples with lower Lyso concentrations (up to 2 % w/w), a small decrease on the main transition temperature (T m) was observed, whereas T m increased by further addition of Lyso (up to 15.0 % w/w). At the same time, an increase of about 20 % in the ΔH of the transition was observed. Pre-transition was also affected in a greater extent by protein presence. When BSA interacted with liposomes, a smaller increase in the T m values was observed with a contemporary increase of about 8 % in the associated ΔH. The data suggested that the BSA–liposomes interaction involves only the external surface of the bilayer, excluding thus any penetration into the liposomal hydrophobic core. On the contrary, a partial penetration into the bilayer is suggested when Lyso is added to liposomes. Both considered proteins strengthened the overall bilayer structure of DMPC liposomes, suggesting a decrease in the membrane permeability. Moreover, Lyso secondary structure changed by interaction with liposomes, as demonstrated by the Raman spectra behaviour, in particular in the case of DMPE.

Keywords: Lysozyme; Bovine serum albumin; Raman spectroscopy; DSC; DMPC; DMPE

Differential scanning calorimetry (DSC) in multiple W/O/W emulsions by A. Schuch; K. Köhler; H. P. Schuchmann (pp. 1881-1890).
Multiple water-in-oil-in-water (W/O/W) emulsions offer a huge potential as encapsulation systems in different food, cosmetic, and pharmaceutical applications. Because of their complex structure, however, it is difficult to characterize these systems. Typical measurement techniques to determine the size and stability of the inner water droplets encapsulated in the oil droplets show limitations and inaccuracies. Determining the total amount of water in the inner droplets is most often done by indirect methods to date. We describe an analytical method based on differential scanning calorimetry (DSC) for characterizing the total amount of encapsulated water droplets and their stability in W/O/W multiple emulsions. It uses the possibility to directly determine the latent heat of freezing of water droplets of the same size and composition as in the multiple emulsions. The amount of water in the inner droplets of a W/O/W emulsion can thus be calculated very accurately. It is shown that this method enables furthermore detecting multi-modalities in the size distribution of inner water droplets in W/O/W emulsions. Changes in droplet size distribution of the inner droplets occurring during the second emulsification step of processing or during storage can be detected. DSC thus offers a powerful tool to characterize the structure of multiple W/O/W emulsions.

Keywords: Multiple emulsion; Measurement; Encapsulation efficiency; Differential scanning calorimetry (DSC); Droplet size distribution

Examination of proliferation of probiotic microbes by isoperibolic calorimetry by B. Schäffer; L. Daróczi; B. Keller; Z. Szakály; D. Lőrinczy (pp. 1891-1896).
Due to the increasing consumers’ interest in up-to-date nutrition nowadays the production of main part of fermented dairy products (e.g. yogurt, kefir) is performed using probiotic microbes. The majority of this product group are the flavoured variations, the sweetener is, first of all, still refined sugar (e.g. saccharose). Honey of natural origin, consequently preferred from the nutrition-physiological point of view, could be proposed to replace this refined carbohydrate. To check its availability for this purpose the growth of microbes of the Hungarian culture of trade name Prebiolact-2 was examined. The probiotic properties of the culture are proved by clinical tests. At the determination of recipes of control and experimental samples we took into consideration that the milk composition and carbohydrate content of samples should have been the same, and they could differ only in carbohydrate-free component content of honey. During processing of the samples the minimum heat-treatment was applied to protect the biologically active components of honey to the greatest degree. Pasteurized-homogenized milk was used as raw material, in which granulated sugar and the honeys were solved, respectively, at 60 °C. The inoculation was made by Prebiolact-2 culture injected into the batch-wessel; the closed cells were agitated intensively for 10 s. General conclusion of thermal investigation is that the proliferation rate is longer lasting in case of honey treated milks. The acacia- honey resulted in the same probiotic proliferation as sugar did. In case of other herb-honeys the effect was smaller, very probably because of the strong bactericidal effect of herbs, which is very important from medical point of view. According to the results of the consumer survey over 85 % of them think that the consumption of herbs in the form of honey is especially beneficial from both dietary and market view.

Keywords: Isoperibolic calorimetry; Proliferation of probiotic bacteria; Honey; Sugar

Differential scanning calorimetric examination of pathologic scar tissues of human skin by N. Wiegand; I. Naumov; L. G. Nőt; L. Vámhidy; D. Lőrinczy (pp. 1897-1902).
Keloid and hypertrophic scarring is a dermal fibroproliferative disorder characterized by increased fibroblast proliferation and excessive production of collagen. Excess scar formation occurs after dermal injury as a result of abnormal wound healing. Keloid formation has been ascribed to altered growth factor regulation, aberrant collagen turnover, genetics, immune dysfunction, sebum reaction, and altered mechanics. No single hypothesis adequately explains keloid formation. The thermal denaturations of pathologic human skin scar tissues were monitored by a SETARAM Micro DSC-II calorimeter. All the experiments were performed between 0 and 100 °C. The heating rate was 0.3 K min−1. DSC scans clearly demonstrated significant differences between the different types and conditions of samples (intact skin: T m = 54.8 °C and ΔH cal = 4.5 J g−1; normal scar: T m = 53.8 °C and ΔH cal = 4.2 J g−1; hypertrophic scar: T m = 54.2 °C and ΔH cal = 2.4 J g−1; keloid: T m = 52.9 °C and ΔH cal = 8.3 J g−1). The heat capacity change between native and denatured states of samples increased with the degree of structural alterations indicating significant water loosing. These observations could be explained with the structural alterations caused by the biochemical processes. With our investigations, we could demonstrate that DSC is a useful and well-applicable method for the investigation of collagen tissue of the human keloid and hypertrophic scar tissues. Our results may be of clinical relevance in the future, i.e., in the diagnosis of the two different pathologic scar formations, or in the choice of the optimal therapy of the disease.

Keywords: Keloid; Hypertrophic scar; Wound healing; DSC

Influence of the nanoparticle type on the thermal decomposition of the green starch/poly(vinyl alcohol)/montmorillonite nanocomposites by Manuela-Tatiana Nistor; Cornelia Vasile (pp. 1903-1919).
In this study, some aspects concerning the thermal decomposition of starch/poly(vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites with 2 wt% nanoclay, prepared by melt mixing method, were studied. For these loadings, the inorganic fillers are well dispersed through the PVA/starch matrix, i.e., the nanocomposites formed are mostly intercalated hybrids. The aim of this article is to establish the effect of the nanofiller nature on the thermal decomposition of the starch/PVA/MMT nanocomposites. The thermal behavior of the 50 wt% starch/50 wt% PVA blend and its nanocomposites with 2 wt% nanoclay has been investigated by thermogravimetric analysis coupled with Fourier transform-infrared spectroscopy and mass spectrometry (MS). The volatile compounds resulting during the thermal degradation were studied by in situ vapor phase FT-IR spectroscopy and MS technique under a controlled temperature/time program. Apart from the identification of the volatile compounds, some conclusions on the nanoclays effect on the degradation mechanism and formation of the volatile compounds in accordance with the previously developed general mechanisms for PVA and starch degradation have been formulated. The clay–PVA/starch nanocomposites show completely different degradation product distribution patterns, which may be attributed to the presence of the head-to-head structures and Si–O–C linkages formed between clay and blend components.

Keywords: Nanocomposites; Decomposition; Mechanism; TG; FT-IR; MS

The effect of temperature on the mechanical properties of a protein-based biopolymer network by Fernando G. Torres; Omar P. Troncoso; Maribella R. Montes (pp. 1921-1925).
Several studies have shown that eggshell membrane (ESM) is a suitable biomaterial with potential applications in biomedicine such as wound repair and cell culture. In order to control and improve the use of ESM for biomedical applications their physical and structural properties must be known. In this paper, we have studied the effect of temperature on the mechanical properties of the ESM. Atomic force microscopy was used to assess the morphology of the ESM. The mechanical properties of the membranes were studied by means of uniaxial tensile tests carried out at four different temperatures. Differential scanning calorimetry and thermo-gravimetrical analysis were used to assess the thermal transitions of the ESM and the influence of the water content on its thermal behavior. The Young’s modulus showed a linear inverse dependence with regard to the temperature of the sample. A peak associated to the thermal denaturation of collagen was observed in the DSC tests of the membrane. These peaks showed a dependence on the water content of the specimens.

Keywords: Eggshell membrane; Collagen; Thermal transition

Thermal decomposition of new chlorido(p-cymene) ruthenium(II) complexes containing N-alkylphenothiazines by Berta Holló; Milena Krstić; Sofija P. Sovilj; Katalin Mészáros Szécsényi (pp. 1927-1932).
The thermal decomposition of [RuCl26-p-cymene)]2 (1) and its biologically active N-alkylphenothiazine compounds of composition L[RuCl36-p-cymene)] where L = CPH+ (2), TFH+·HCl (3), and TRH+ (4) (chlorpromazine hydrochloride, CP·HCl; trifluoperazine dihydrochloride, TF·2HCl; and thioridazine hydrochloride, TR·HCl, respectively) has been studied. The crystal and molecular structure of compound 3 was determined earlier by single crystal X-ray diffraction analysis. The thermal data were collected by simultaneous TG/DSC measurements. For evolved gas detection, the qualitative reaction of chlorides with AgNO3 in an acidic solution was applied. The measurements were carried out in the temperature range to 700 °C in nitrogen atmosphere. Compounds of L[RuCl36-p-cymene)] crystallize with water or water/2-propanole. On the basis of thermal data, the trend in the solvent bonding energies was assessed.

Keywords: Ruthenium(II) complexes; N-alkylphenothiazines; Thermal decomposition; EGD

Thermal behavior of furosemide by Rita de Cássia da Silva; Felipe Silva Semaan; Csaba Novák; Eder Tadeu Gomes Cavalheiro (pp. 1933-1937).
Data from theoretical, thermal, and spectroscopic methods were compared in order to map a possible mechanism for the thermal decomposition of furosemide, a diuretic compound, in solid state. TG/DTG curves suggested a two-stage decomposition process. The first product of decomposition is water (m/z = 18), released due to a dimerization resulting in the formation of an amide. Then carbon dioxide (m/z = 44), nitroxide (m/z = 30), and 2-methyl-furanyl ion (m/z = 81) are released in the second stage. The chlorine substituted benzene ring, due to the double bond conjugated system, being the last fraction to decompose. Theoretical calculations presented are in agreement with experimental results.

Keywords: Furosemide; Decomposition mechanism; TG–MS combined technique

Characteristics and kinetics analysis of Codonopsis pilosula pyrolysis by Yingli Wang; YuYing Zhao; Yongquan Zuo; Liping Chang (pp. 1939-1945).
Eight kinds of Radix Codonopsis (RC) from different origins in China were selected as the experimental samples fort his study. Their pyrolysis processes were researched by the method of thermogravimetry analysis, in which the heating course was set in the ways of programming temperature from room temperature to 500 °C at different heating rates. Research results show that the process in the heating period of RC includes three stages: water loss, fast pyrolysis, and medium rate decomposition. For cultivated RC, the average initial decomposition temperature in the fast pyrolysis stage is 115 °C, whereas the peak temperature of the fast pyrolysis stage is changed from 189 to 225 °C, in which stage the alcohol-soluble substances are mainly decomposed. It is required to control the operational temperatures of drying and concocting processes according to initial decomposition temperature. Kissinger–Akahira–Sunose model can be used to describe the process mechanism of RC pyrolysis, and the kinetic analyses based on the fast pyrolysis stage thermogravimetric data show that the activation energies change from 141 to 207 kJ mol−1 for cultivated RC samples and 122 to 131 kJ mol−1for wild RC samples. The alcohol-soluble extract (ASE) content of wild RC samples is lower than that of cultivated RC samples; their thermal stability is also relatively poor.

Keywords: Radix Codonopsis; Kinetics; Thermogravimetry analysis; Alcohol soluble extraction

Microcalorimetric study of the effect of artesunate on the growth metabolism of mitochondria isolated from rat liver by Xuesong Shen; Meihua Jin; Chunxia Zhao; Xinqiang Tan; Hanfu Liu; Xuelian Qin; Zhuangpingi Qiu; Yi Liu (pp. 1947-1952).
In this study, the metabolic thermogenic curves of mitochondria isolated from rat liver tissue were drawn, and the effects of artesunate on metabolic activity of mitochondria were studied using TAM Air Isothermal Microcalorimeter. After isolation from the rat liver, mitochondria still have metabolic activity and can live for a week with appropriate nutrients. With the addition of artesunate (7.5 μM/mL), the metabolic activity of mitochondria was completely lost at this concentration. From the thermogenic curves, we obtained the thermokinetic equations under different conditions: T max = 2512.24 + 1761.53c, R = 0.9375; and Tlag (min) = 707.26 + 285.17c, R = 0.9846. The results showed that artesunate was a mitochondria-targeted drug having obvious effects on mitochondrial metabolism.

Keywords: Microcalorimetry; Artesunate; Mitochondria; Thermokinetics

Thermal analysis of interaction between 2-PAM chloride and various excipients in some binary mixtures by TGA and DSC by Pranav Kumar Gutch; Sharma Jitendra; Shrivastava Alankar; Jain Anurekha; K. Ganesan (pp. 1953-1958).
Pralidoxime chloride known as 2-PAM chloride is used as antidote for nerve agent’s poisoning. This study was undertaken to establish the compatibility of 2-PAM chloride with a number of commonly used excipients by using thermoanalytical technique viz., differential scanning calorimetry (DSC) and thermogravimetry/differential thermogravimetry (TG/DTG) used in pharmaceutical formulation. The TG and DSC both results demonstrated that polyvinyl alcohol, polyacrylamide, microcrestline cellulose, hydroxypropyl cellulose, cellulose acetate, ethyl cellulose found to be compatible with 2-PAM chloride and chosen for the preparation of antidote against chemical warfare agents.

Keywords: Differential scanning calorimetry (DSC); Thermogravimetry/differential thermogravimetry (TG/DTG); 2-PAM chloride; Compatibility study; Chemical warfare agents

Investigation of thermal behavior of Heliotropium indicum L. lyophilized extract by TG and DSC by Russany Silva da Costa; Charles Alberto Brito Negrão; Sarah Regina Pereira Camelo; Roseane Maria Ribeiro-Costa; Wagner Luiz Ramos Barbosa; Carlos Emmerson Ferreira da Costa; José Otávio Carréra Silva Júnior (pp. 1959-1964).
Thermogravimetric (TG) techniques and differential scanning calorimetry (DSC) used for the study of pre-formulation or drug–adjuvant compatibility have been gaining importance in Brazil. These techniques are being used for the verification of possible interactions between drugs and adjuvants. Aiming at studying the behavior of a plant extract and its mixture with adjuvants, using these thermoanalytical techniques the plant species Heliotropium indicum L. was used. This plant which is originally from India and has been well acclimatized in Brazil has healing and anti-inflammatory properties. The methodology for obtaining the extract followed the Brazilian Pharmacopoeia methodology. And the incorporation of the extract with adjuvants was through binary mixtures (1:1 w/w). The TG and DSC curves were obtained under nitrogen atmosphere (25 mL min−1) at a heating rate of 5 °C min−1; TG tests were analyzed within a temperature range from 25 to 600 °C and DSC from 25 to 300 °C. The TG curves show good thermal stability of the extract and its mixtures with adjuvants up to 150 °C, except the propylene glycol (PLG). The DSC curves revealed an incompatibility of the extract with methylparaben and PLG mixture.

Keywords: TG; DSC; Adjuvants; Extract; Heliotropium indicum

Determination of calcium content in tablets for treatment of osteoporosis using thermogravimetry (TG) by S. P. M. C. de Souza; F. E. de Morais; E. V. dos Santos; C. A. Martinez-Huitle; N. S. Fernandes (pp. 1965-1970).
Tablets containing calcium carbonate are widely used in the treatment of osteopenia and osteoporosis. In the present study, the samples (AM-1, AM-2, AM-3) were characterised by Fourier transform infrared absorption spectra, thermogravimetry, differential thermal analysis, differential scanning calorimetry and X-ray diffraction powder patterns. TG curves were used to quantify the percentage of calcium. The results of thermogravimetry were consistent with the data obtained by inductively coupled plasma-optical emission spectroscopy ICP-OES, indicating the possibility that these techniques can be used to determine calcium in tablets containing calcium carbonate.

Keywords: Osteoporosis; Calcium; Thermogravimetry; ICP-OES

Influence of temperature and humidity on the degradation process of ascorbic acid in vitamin C chewable tablets by Gorica Pavlovska; Stojne Tanevska (pp. 1971-1977).
Ascorbic acid (AA) is the active ingredient of vitamin C chewable tablets. It is unstable even at room temperature, and increased temperature and humidity rapidly increase its degradation. To protect the active substance, we made its coating with polymers ethyl cellulose that provides its thermal protection and protection from moisture. We bet each particle of AA with a layer of polymer by the method of fluidization. Extra protection against thermal effects and penetration of moisture and oxygen provides the packaging. By using four kinds of packaging: polypropylene container for tablets, strips of aluminum and polyvinyl chloride Al/PVC strips, glass bottles, and strips of aluminum and polyethylene (Al.PE/PE.Al) of 3, of 6 months and of 12 months. One of the tablets are stored at room temperature (25 ± 2 °C/60% RH ± 5%), and the rest in terms of accelerated aging or increased temperature and humidity (30 ± 2 °C/65% RH ± 5% and 40 ± 2 °C/75% RH ± 5%). The speed of degradation of unprotected AA usually get doubled when there is increasing of the temperature for every 10 °C. Experimentally the concentration of AA was monitored, its oxidation product-dehydroascorbic acid and its degradation product-diketogulonic acid.

Keywords: Ascorbic acid; Dehydroascorbic acid; Chewing tablets; Oxidation; Degradation

Thermal stability of ketoprofen by Dumitru Tiţa; Adriana Fuliaş; Bogdan Tiţa (pp. 1979-1985).
The purpose of this investigation is to calculate the kinetic parameters and the kinetic model for the studied process. The results are further used to predict the system’s behaviour in various circumstances. A kinetic study regarding the ketoprofen—involving active substance’s thermal decomposition—was performed under isothermal conditions and in a nitrogen atmosphere, for the temperature steps: 260; 265; 270; 275; and 280 °C. The thermogravimetry/derivative thermogravimetry data were processed by three differential methods: isothermal–isoconversional, Friedman’s isothermal–isoconversional, and isothermal model-fittings. The obtained results are in good accordance with those obtained under non-isothermal conditions of a previous study, and confirm the necessity for the kinetic parameters to be determined, under different thermal conditions, by the adequate calculation methods.

Keywords: Ketoprofen; TG/DTG/DTA; Isothermal; Non-isothermal; Kinetic study

Characterization of crystalline and amorphous content in pharmaceutical solids by dielectric thermal analysis by Manik Pavan Maheswaram; Dhruthiman Mantheni; Indika Perera; Hareesha Venumuddala; Alan Riga; Kenneth Alexander (pp. 1987-1997).
Morphological and thermodynamic transitions in drugs as well as their amorphous and crystalline content in the solid state have been distinguished by thermal analytical techniques, which include dielectric analysis (DEA), differential scanning calorimetry (DSC), and macro-photomicrography. These techniques were used successfully to establish a structure versus property relationship with the United States Pharmacopeia standard set of active pharmaceutical ingredient (API) drugs. A distinguishing method is the DSC determination of the amorphous and crystalline content which is based on the fusion properties of the specific drug and its recrystallization. The DSC technique to determine the crystalline and amorphous content is based on a series of heat and cool cycles to evaluate the drugs ability to recrystallize. To enhance the amorphous portion, the API is heated above its melting temperature and cooled with liquid nitrogen to −120 °C (153 K). Alternatively a sample is program heated and cooled by DSC at a rate of 10 °C min−1. DEA measures the crystalline solid and amorphous liquid API electrical ionic conductivity. The DEA ionic conductivity is repeatable and differentiates the solid crystalline drug with a low conductivity level (10−2 pS cm−1) and a high conductivity level associated with the amorphous liquid (106 pS cm−1). The DSC sets the analytical transition temperature range from melting to recrystallization. However, analysis of the DEA ionic conductivity cycle establishes the quantitative amorphous and crystalline content in the solid state at frequencies of 0.10–1.00 Hz and to greater than 30 °C below the melting transition as the peak melting temperature. This describes the “activation energy method.” An Arrhenius plot, log ionic conductivity versus reciprocal temperature (K−1), of the pre-melt DEA transition yields frequency dependent activation energy (E a, J mol−1) for the complex charging in the solid state. The amorphous content is inversely proportional to the E a where the E a for the crystalline form is higher and lower for the amorphous form with a standard deviation of ±2%. There was a good agreement between the DSC crystalline melting, recrystallization, and the solid state DEA conductivity method with relevant microscopic evaluation. An alternate technique to determine amorphous and crystalline content has been established for the drugs of interest based on an obvious amorphous and crystalline state identified by macro-photomicrography and compared to the conductivity variations. This second “empirical method” correlates well with the “activation energy” method.

Keywords: Dielectric analysis (DEA); Differential scanning calorimetry (DSC); DEA ionic conductivity; Crystalline solid; Amorphous; Amorphous liquid; Semicrystalline; Amorphous and crystalline content; Activation energy; Empirical method

Thermal, phase transition, and thermal kinetics studies of carbamazepine by Wenju Liu; Leping Dang; Hongyuan Wei (pp. 1999-2004).
The thermal, phase transition of carbamazepine dihydrate and the solid-state transformation of carbamazepine from form III to form I were performed by Differential scanning calorimetry (DSC), Thermo gravimetry (TG–DTA), and X-ray powder diffraction.The non-thermal kinetic analysis of carbamazepine dihydrate and form III was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The model-free model, the Kissinger method, was used to give the Arrhenius parameters. Arrhenius plots from the kinetic model yielded activation energies corresponding to dehydration of dihydrate and melting of anhydrate CBZ form I were 95.28, 966.06 kJ mol−1, the pre-exponential factors were 8.34E+11 and 1.41E+149, respectively. For the transformation of carbamazepine from form III to form I, activation energies corresponding to the melting of CBZ form III, recrystallization of form I, and melting of form I were 1160.81, 710.89, 1265.89 kJ mol−1, the pre-exponential factors were 2.29E+144, 4.43E+91, and 1.61E+151, respectively. As a comparison, Ozawa method was used to verify the activation energy values obtained by Kissinger method. The result shows a close activation energy values between two methods.

Keywords: Carbamazepine; Thermal studies; Phase transitions; Thermal kinetic analysis

Melting of orthorhombic betulin by V. A. Drebushchak; M. A. Mikhailenko; Tatyana P. Shakhtshneider; Svetlana A. Kuznetsova (pp. 2005-2008).
Orthorhombic (s.g. P 21 21 2, a = 28.6145 Å, b = 27.4115 Å, c = 6.9536 Å, V = 5454.1 Å3) betulin (C30H50O2) was found in this study to melt at 245 °C with the enthalpy of fusion 40.3 J mol−1. The shape of the peak of melting gives rise to the belief that there are several polymorphs of betulin.

Keywords: Betulin; DSC; Enthalpy of fusion; Melting point; Polymorphism

Sodium ibuprofen dihydrate and anhydrous by Roberta Censi; Valentina Martena; Ela Hoti; Ledjan Malaj; Piera Di Martino (pp. 2009-2018).
(R,S)-(±)-ibuprofen sodium salt (racemate) dihydrate (SID) was dehydrated and the physicochemical properties of SID and the anhydrous forms (SIA) were compared by different analytical techniques (scanning electron microscopy, helium pychnometry, differential scanning calorimetry, X-ray powder diffractometry). The dehydration of SID, followed by thermogravimetry in isothermal conditions, allowed to calculate the activation energy of the dehydration process and to predict the mechanism of dehydration. Dehydration occurred in one step and the activation energy was rather low, indicating the ease of water removal from the crystal. The mechanism of dehydration followed a three dimensional diffusion (Jander equation). Similarly to the dehydration, the hydration process was followed under isothermal conditions by exposing the anhydrous powder at 64% RH at different temperatures. The mechanism of hydration was governed by a two dimensional diffusion and the energy associated to the process was very low, indicating the ease of crystal hydration. The driving force for the hydration is higher than that for the dehydration. From a thermodynamic point of view this fact may explain why the hydrated form is more stable than the anhydrous one. Solubilities, determined at different temperatures in water and in phosphate buffer (pH 6.8), showed that SID is more soluble in water than SIA for temperatures higher than approximately 283 K. On the contrary, in phosphate buffer SIA is always more soluble than SID in the temperature range considered for the experiments. Drug release reflects the solubility in water and phosphate buffer previously reported.

Keywords: Sodium ibuprofen; Hydration; Dehydration; Activation energy; Solubility; Dissolution

Thermal behavior of some antihistamines by G. L. Perpétuo; D. A. Gálico; R. A. Fugita; R. A. E. Castro; M. E. S. Eusébio; O. Treu-Filho; A. C. M. Silva; G. Bannach (pp. 2019-2028).
Thermogravimetry (TG), differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), as well as X-ray powder diffraction (XRD) and Fourier transformed infrared spectroscopy (FTIR) were used to study the thermal behavior and the chemical structure of cimetidine, famotidine, ranitidine-HCl, and nizatidine. The TG–DSC curves show that the famotidine and ranitidine-HCl suffer decomposition during melting and they are thermally less stable in comparison with cimetidine and nizatidine, the latter being the most stable of all the drugs studied in this study. The DSC curves of famotidine and ranitidine-HCl show exothermic peaks immediately after the melting, confirming the occurrence of thermal decomposition. The DSC curves also show that the cimetidine and nizatidine have some thermal stability after melting. The thermal events shown in the PLTM images are consistent with the results shown in the TG–DSC and DSC curves. The XRD patterns show that the cimetidine and famotidine are less crystalline compared with ranitidine-HCl and nizatidine. The theoretical FTIR bands are in agreement with those obtained experimentally, and in some cases, no difference is observed between the theoretical and experimental values, even being identical in one of the cases.

Keywords: Antihistamines; Thermal behavior; Cimetidine; Famotidine; Ranitidine; Nizatidine

Isothermal titration calorimetry (ITC) study of natural cyclodextrins inclusion complexes with drugs by Małgorzata Wszelaka-Rylik; Paweł Gierycz (pp. 2029-2035).
Isothermal titration calorimetry (ITC) was used to characterize inclusion complex formation of natural cyclodextrins (α- and β-cyclodextrin) with three drugs ((+)brompheniramine, (±)brompheniramine, cyclopentolate) in aqueous solutions. ITC measurements were carried out at 298.15 K on a Microcal OMEGA ultrasensitive titration calorimeter (MicroCal Inc.). The experimental data were analyzed on the basis of the model of a single set of identical sites (ITC tutorial guide). β-CD forms inclusion complexes of stoichiometry 1:1 with the all investigated drugs. In turn, smaller molecule of α-CD forms inclusion complexes of two different stoichiometry: with bigger molecules ((+)brompheniramine and (±)brompheniramine) of a stoichiometry 2:1 and with smaller molecules (cyclopentolate) of a stoichiometry 1:2. Based on the experimental values of equilibrium constant (K) and enthalpy of complex formation (ΔH), the Gibbs energy of complex formation (ΔG), and the entropy of complex formation (ΔS), have been calculated, for all the investigated systems. Obtained results showed that complex formation of β-CD (bigger molecule with wider cavity compared to β-CD) with both (+)brompheniramine, (±)brompheniramine, and cyclopentolate is enthalpy driven while complexes of α-CD with the all investigated drugs are enthalpy-entropy stabilized. This indicated that the difference in the cavity dimensions is reflecting in different driving forces of complex formation and binding modes what resulted in different stoichiometry of the obtained inclusion complexes.

Keywords: Isothermal titration calorimetry (ITC); α-Cyclodextrin; β-Cyclodextrin; (+)Brompheniramine; (±)Brompheniramine; Cyclopentolate; Inclusion complexes

Compatibility of sildenafil citrate and pharmaceutical excipients by thermal analysis and LC–UV by Tamíris A. Júlio; Igor F. Zâmara; Jerusa S. Garcia; Marcello G. Trevisan (pp. 2037-2044).
The evaluation of sildenafil citrate (SC), the best-selling drug for treatment of impotence, for compatibility with various excipients was investigated using thermal and isothermal stress testing. Differential scanning calorimetry (DSC), hot-stage microscopy (HSM) and liquid chromatography (LC) with ultraviolet detection were successfully employed to investigate the compatibility between SC and various excipients commonly used in solid form in the pharmaceutical industry. The studies were performed using 1:1 (m/m) drug/excipient physical mixtures and samples were stored under accelerated stability conditions (40 °C at 75% relative humidity). All excipients tested (such as colloidal silicon dioxide, croscarmellose sodium, lactose, mannitol and sucrose) showed potential incompatibilities by DSC and LC analysis after accelerated stability testing. However, some incompatibilities were not detected by the DSC method and were observed only when LC analysis was performed. HSM was able to differentiate active pharmaceutical ingredient degradation from solubilisation, supporting the interpretation of DSC in excipients where thermal events either overlapped or disappeared. The combination of both the analytical techniques (DSC and LC) and use of a stability chamber is extremely helpful in detecting incompatibilities and providing more robust and accurate approaches for pre-formulation studies.

Keywords: Sildenafil citrate; Thermoanalysis; Isothermal stress testing; Incompatibilities; Pre-formulation; Hot-stage microscopy

Moisturizing emulsion systems based on the novel long-chain alkyl polyglucoside emulsifier by Milica Lukic; Ivana Pantelic; Rolf Daniels; Christel Müller-Goymann; Miroslav Savic; Snezana Savic (pp. 2045-2057).
Mesomorphic behavior of the novel long-chain alkyl polyglucoside emulsifier comprising arachidyl alcohol (C20), behenyl alcohol (C22), and arachidyl glucoside was investigated in order to determine the prevalent stabilization mechanism and moisturizing capacity of emulsion systems based on it. For this to be accomplished thermoanalytical methods (differential scanning calorimetry and thermogravimetric analysis) coupled with microscopy, rheological, X-ray diffraction methods and a short-term in vivo study of skin hydration level were performed. Obtained results have proved that C20/C22 alkyl polyglucoside mixed emulsifier is able to provide the synergism between the two main types of lamellar phases, the liquid-crystalline (Lα), and the gel crystalline (Lβ) one, building the emulsion systems of different stability and performance. Formation of lamellar structures influenced for more than one half of water within the system to be entrapped. Conducted investigation of hydration potential in real-time conditions provided valuable information on the investigated emulsion vehicles’ moisturizing potential as well as their contribution to the skin barrier improvement. Therefore, it could be expected that emulsions based on this alkyl polyglucoside emulsifier could influence the delivery of active ingredients of both the lipophilic and hydrophilic type. The employment of thermoanalytical methods in our work suggests the possibility for thermal methods to be used more frequently in the characterization of both the novel raw materials and the belonging emulsion systems.

Keywords: Alkyl polyglucoside emulsifier; Moisturizing capacity; Emulsions; Thermal methods

Low-temperature heat capacity and thermodynamic parameters of γ-aminobutyric acid by I. E. Paukov; Yu. A. Kovalevskaya; E. V. Boldyreva (pp. 2059-2062).
Thermodynamic properties of γ-aminobutyric acid were studied in the temperature interval from 5.7 to 300 K using a vacuum adiabatic calorimeter. The curve C p (T) in the mentioned temperature interval is S-shaped without any anomalies. Based on the smoothed values of heat capacity, the calorimetric entropy $$ S_{m}^{0} (T) - S_{m}^{0} (0) $$ and the difference in the enthalpies $$ H_{m}^{0} (T) - H_{m}^{0} (0) $$ were calculated and tabulated. At the standard temperature 298.15 K, these values are equal to 158.1 ± 0.3 J K−1 mol−1 and 23020 ± 50 J mol−1, respectively. At temperatures from 5 to 10 K, the function C p (T) was found to obey the Debye law C = AT 3. Contrary to what has been supposed previously, the empirical Parks–Huffman rule for estimating entropy in the homologous series was shown to be not valid for the series glycine–β-alanine–γ-aminobutyric acid.

Keywords: Amino acids; Heat capacity; Low temperatures; Thermodynamic functions

Thermodynamic analysis of lipoic acid crystallized with additives by Jinyan Zhang; Leping Dang; Hongyuan Wei (pp. 2063-2068).
Differential scanning calorimetry (DSC) was used as a screening technique to study the interaction between lipoic acid and amino acids. The samples containing lipoic acid and amino acids were prepared by two different methods (milling method and cooling crystallization method). Firstly, cooling method was used to prepare the sample with amino acids as additives. DSC results indicated that only phenylalanine has some interaction with lipoic acid. Further, in order to study the interaction between lipoic acid and phenylalanine, another method (milling method) was used to prepare the sample containing phenylalanine, and the effect of sample preparation methods was studied through IR analysis and the X-ray powder diffraction. On the basis of above researches, the possible interaction mechanisms between lipoic acid and phenylalanine were proposed.

Keywords: Lipoic acid; Amino acid; Thermodynamic analysis; Cooling method; Milling method

Chrysophanol–phospholipid complex by Devendra Singh; M. S. M. Rawat; Ajay Semalty; Mona Semalty (pp. 2069-2077).
Delivery of poorly soluble drugs results in poor absorption and low bioavailability to the systemic circulation. Chrysophanol (1,8-dihydroxy 3-methyl anthraquinone) a plant derived herbal drug is well known for its strong anti-inflammatory, anti-mutagenic, and anti-carcinogenic activities but poor aqueous solubility (hence the lower dissolution rate), is a major barrier in its intestinal absorption. To improve the bioavailability and prolong its duration in the body system, its phospholipid complex was prepared and evaluated for various physicochemical parameters like encapsulation efficiency, scanning electron microscopy, differential scanning calorimetry (DSC), X-ray powder diffractometry (X-RPD), IR spectroscopy, aqueous/n-octanol solubility, and dissolution study. The phospholipid complex of chrysophanol was found, fluffy and porous with rough surface morphology. FTIR, DSC, and X-RPD data confirmed the complex formation. The 89.1 % of chrysophanol was encapsulated in the phospholipid complex. The aqueous solubility of chrysophanol was improved from 0.60 to 30.09 μg ml−1 in the prepared complex. The improved dissolution was shown by the complex (which showed continuous release up to 83.67 % of chrysophanol) at the end of 12 h, in comparison to free drug (which showed a total of only 45.12 % drug release at the end of 12 h of dissolution study).

Keywords: Anthraquinone; Herbal drug; Phosphatidylcholine; Amorphous system; Dissolution; DSC; X-RPD

Synthesis, spectroscopic, and thermal investigation of transition and non-transition complexes of metformin as potential insulin-mimetic agents by Foziah A. Al-Saif; Moamen S. Refat (pp. 2079-2096).
Complexes of [Mn(MF)2(Cl)2]·2H2O (1), [Fe(MF)2(Cl)2]Cl·4H2O (2), [Ni(MF·HCl)2(Cl)2]·6H2O (3), [Cu(MF·HCl)2(Cl)2] (4), [Zn(MF·HCl)2](NO3)2·6H2O (5), [Cd2(MF·HCl)(Cl)4(H2O)] (6), [Mg(MF·HCl)2(Cl)2]·6H2O (7), [Sr2(MF·HCl)(Cl)4(H2O)] (8), [Ba(MF·HCl)2(Cl)2]·2H2O (9), [Pt(MF)4] (10), [Au(MF)3]Cl3 (11), and [Pd(MF)2]Cl2 (12) were synthesized from Legitional behavior of metformin drug as a diabetic agent. The authenticity of the transition and non-transition metal complexes were characterized by elemental analyses, molar conductivity, (infrared, UV–Vis) spectra, effective magnetic moment in Bohr magnetons, electron spin resonance, thermal analysis, X-ray powder diffraction as well as scanning electron microscopy. Infrared spectral studies as well as elemental analyses revealed the existence of metformin in the base or hydrochloride salt forms in the chelation state acts as a bidentate ligand while the platinum(IV) complex is coordinated through the deprotonation of –NH group. The magnetic and electronic spectra of Mn(II), Fe(III), Ni(II), and Cu(II) complexes suggest an octahedral geometry. Antimicrobial screening of metformin and its complexes were determined against the (G+ and G) bacteria (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa) and fungi (Aspergillus flavus and Candida albicans).

Keywords: Metformin; Transition and non-transition metals; Thermal studies; Spectroscopic investigation; Antimicrobial test

Thermal characterization of mangaba-based films by Mateus Santos Melo; Roneval Félix de Santana; Cinthia Meireles Batista; M. S. Pinheiro; R. L. C. Albuquerque Jr.; Francine Ferreira Padilha; Álvaro Silva Lima; Paula Santos Nunes; L. P. Costa; A. A. S. Araújo; Juliana Cordeiro Cardoso (pp. 2097-2102).
The purpose of this study was to evaluate the physical–chemical properties of starch (SF), mangaba (MF), and mangaba/starch-based films (MSF), using differential thermal analysis, thermogravimetry/derivative thermogravimetry, infrared spectroscopy, mechanical profile, and scanning electron microscopy. The films were prepared by casting process using sucrose and propyleneglycol as plasticizers. The thermal profiles of MF and MSF were similar and showed increased thermal stability. The mechanical properties of MF and MSF presented decreases of tensile strength and elastic modulus when compared with SF. The MSF showed the best thermal and mechanical characteristics.

Keywords: Mangaba; Films; Thermal analysis

Compatibility study of quetiapine fumarate with widely used sustained release excipients by M. C. Gohel; T. M. Patel (pp. 2103-2108).
The drug-excipient compatibility study of quetiapine fumarate, with widely used sustained release excipients, was carried out employing differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The selected excipients were HPMC K100M, sodium alginate, xanthan gum, Eudragit RSPO, hydrogenated castor oil, carnauba wax, and PEO WSR 303. Equal proportion of drug and excipients was utilized in the interaction study. FT-IR spectra indicated the absence of interaction between drug and excipients. The DSC curve showed a sharp endothermic melting peak at 173.26 °C for quetiapine fumarate. Post melting interaction was observed for carnauba wax, Eudragit RSPO, and hydrogenated castor oil probably due to solubilization of drug in the melted excipient. No interaction was observed for other excipients. The physical mixtures stored at 30 ± 2 °C/65 ± 5% RH did not show any significant degradation of the drug. The concept of systemically conducted preformulation studies will facilitate dossier submission to the drug control authority.

Keywords: Compatibility; Quetiapine fumarate; Sustained release; DSC; FT-IR

Compatibility study between trandolapril and natural excipients used in solid dosage forms by Eleftheria Roumeli; Angelina Tsiapranta; Eleni Pavlidou; Georgios Vourlias; Kyriakos Kachrimanis; Dimitrios Bikiaris; Konstantinos Chrissafis (pp. 2109-2115).
Thermal analysis is an essential, analytic tool used in preliminary studies and preparation of new pharmaceutical formulations. This study was performed to investigate the possible interactions between trandolapril and three commonly used natural excipients, namely α-lactose monohydrate, microcrystalline cellulose, and pregelatinized starch. The compatibility studies were carried out using thermoanalytic along with other complementary techniques. Differential scanning calorimetry and thermogravimetric analysis have proved that trandolapril is fully compatible with all the studied excipients until 100 °C. The complementary techniques used in this study were X-ray powder diffraction, Fourier transform-infrared spectroscopy, and scanning electron microscopy which confirmed the findings of thermal analysis.

Keywords: Trandolapril; Excipients; Compatibility studies; Thermogravimetric analysis; Differential scanning calorimetry

Evaluation of thermal stability and parameters of dissolution of nifedipine crystals by Renata Da Silva Leite; Rui De Oliveira Macedo; Sandro Marden Torres; Caio Cesar Neves Batista; Lays De Oliveira Baltazar; Severino Antônio Lima Neto; Fábio Santos De Souza (pp. 2117-2123).
Nifedipine is a calcium channel blocker as well as a powerful vasodilator used to treat ischemic heart disease and hypertension. Its photosensitivity and very low solubility in water have been widely acknowledged as important properties deserving improvements. The main thrust of this study is to characterize the nature and the solid-state of nifedipine crystals obtained using different solvents as well as assess the stability by thermal methods (TG and DSC) and crystals structure by means of spectroscopic techniques (MID FTIR and XRD) and assess the dissolution parameters for such crystals. The calculated kinetic parameters activation energy (E a = 123.3 kJ mol−1 ± 0.1), the factor frequency (A = 25.93 ± 0.9 min−1), and the reaction order (n = 0.2) of the main stage of thermal decomposition of nifedipine raw material were performed according to the Ozawa model. The data showed a zero-order kinetic behavior for all crystals despite the different values of E a and A. The dissolution profiles were obtained for such crystals in three dissolution media with different pH values. After 1 h of dissolution, the higher amount of nifedipine dissolved was observed for crystals obtained in isopropyl alcohol (52.5 %, pH 4.5), followed by those in chloroform (48.1 %, pH 1.2) and subsequently in acetone (32.5 %, pH 6.8). Results showed different thermal stabilities and significant variations in the solubility of the crystals.

Keywords: Nifedipine; TG; XRD; Dissolution

Thermal, spectroscopic, and dissolution studies of the simvastatin–acetylsalicylic acid mixtures by Agata Górniak; Bożena Karolewicz; Ewa Żurawska-Płaksej; Janusz Pluta (pp. 2125-2132).
The objective of the present investigation was to study the effect of eutectic formation on in vitro dissolution of simvastatin (SIM) released from mixtures with acetylsalicylic acid (ASA) prepared by a grinding method. SIM–ASA mixtures were characterized by means of differential scanning calorimetry (DSC), infrared spectroscopy (IR), X-ray powder diffractometry (XRPD), and in vitro dissolution tests. IR spectroscopy and XRPD studies indicated no interaction between SIM and ASA in the solid state. The DSC investigation has revealed that SIM and ASA form a simple eutectic system containing 66.6 % w/w of SIM at the eutectic point. In vitro dissolution studies of SIM and its mixtures with ASA were carried out. The eutectic mixture shows an appreciable increase in the dissolution rate in comparison with other ratios and SIM in 0.5 % w/v sodium lauryl sulfate. The dissolution enhancement of SIM was related to the effective wetting of the drug particles with a significantly reduced size released from eutectic composition. In conclusion, dissolution of SIM can be enhanced through eutectic formation with ASA by means of simple mechanical activation (a grinding method).

Keywords: Phase diagram; Eutectic; Simvastatin; Aspirin; Dissolution enhancement; Solid dispersion

Thermoanalytical and spectroscopic studies on different crystal forms of nevirapine by Renu Chadha; Poonam Arora; Monika Garg; Swati Bhandari; Dharamvir Singh Jain (pp. 2133-2142).
This study is aimed at exploring the utility of thermoanalytical methods in the characterization of various polymorphs and solvates of nevirapine. The different forms obtained by recrystallization of nevirapine from various solvents showed morphological differences in SEM. The presence of polymorphic forms is suggested by single sharp melting endotherm different from original sample in DSC and no mass loss in TG, while appearance of desolvation peak in TG indicated the formation of solvates. The higher desolvation temperatures of all the solvates than their respective boiling point indicate tighter binding of solvent. The changes in the crystal lattice were demonstrated by X-ray powder diffraction studies. The enthalpy of fusion rule indicated the existence of monotropy in polymorphic pairs I/O and II/O, while I/II is enantiotropically related. The enthalpy of solution, an indirect measure of the lattice energy of a solid, was well correlated with the crystallinity of all the solid forms obtained. The magnitude of ΔH sol was found to be −14.26  kJ mol−1 for Form V and −8.29  kJ mol−1 for Form O, exhibiting maximum ease of molecular release from the lattice in Form V. The transition temperature was found to be higher than the melting of both the forms except for polymorphic pair I/II providing complementary evidence for the existence of monotropy as well as enantiotropy in these polymorphic pairs.

Keywords: Nevirapine; Thermochemical; Desolvation; Polymorph; Enthalpy

Studies on the thermal behavior and decomposition kinetic of drugs cetirizine and simvastatin by Mohammad Reza Sovizi; Seyed Ghorban Hosseini (pp. 2143-2148).
Understanding the response of drugs and their formulations to thermal stresses is an integral part of the development of stable medicinal products. In the present study, the thermal degradation of two drug samples (cetirizine and simvastatin) was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery/differential thermal analysis (TG/DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the cetirizine occurs during two temperature ranges of 165–227 and 247–402 °C. The TG/DTA analysis of simvastatin indicates that this drug melts (at about 143 °C) before it decomposes. The main thermal degradation for the simvastatin occurs during two endothermic behaviors in the temperature ranges of 238–308 and 308–414 °C. The influence of the heating rate (5, 10, 15, and 20 °C min−1) on the DSC behavior of both the drug samples was verified. The results showed that as the heating rate was increased, decomposition temperatures of the compounds were increased. Also, the kinetic parameters such as activation energy and frequency factor for the compounds were obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa. Based on the values of activation energy obtained by ASTM E696 method, the values of activation energy for cetirizine and simvastatin were 120.8 and 170.9 kJ mol−1, respectively. Finally, the values of ΔS #, ΔH #, and ΔG # of their decomposition reaction were calculated.

Keywords: Non-isothermal; TG/DTA/DSC; Cetirizine; Simvastatin; Drug; Degradation kinetic

Characterization of silver sulfadiazine-loaded solid lipid nanoparticles by thermal analysis by Catenacci Laura; Sorrenti Milena; Bruni Giovanna; Bonferoni Maria Cristina; Sandri Giuseppina; Bettinetti Giampiero (pp. 2149-2155).
The aim of this study is the solid-state characterization of solid lipid nanoparticles (SLN) based on Compritol® 888 (C888) and Lutrol® F68 (F68), loaded with silver sulfadiazine (AgSD), used to develop sponge-like dressings to treat chronic skin ulcers such as decubitis and leg ulcers. Silver compounds like AgSD, in fact, are used to prevent and/or to treat wound colonization that could impair healing, also in the case of antibiotic-resistant bacteria. Thermal analysis, with support from powder X-ray diffractometry and Fourier transform infrared spectroscopy, is used to characterize lipid and drug bulk, unloaded and drug-loaded SLN. In particular, differential scanning calorimetry is used to investigate the degree of crystallinity and the solid-state modification of lipid, two parameters correlated to drug incorporation and drug release rates. The solid-state characterization demonstrates AgSD entrapment in C888 as a core enclosed into F68 shell. AgSD SLN are also stored at different temperatures 25 and 37 °C, respectively, to study the effect of storage conditions, that induce an increase of the lipid crystallinity index correlated to drug release from the lipid matrix.

Keywords: Solid lipid nanoparticles; Silver sulfadiazine; Differential scanning calorimetry; X-ray powder diffractometry; Fourier transform infrared spectroscopy

Moisture and temperature dependence of the dielectric properties of pharmaceutical powders by T. R. A. Magee; W. A. M. McMinn; G. Farrell; L. Topley; Y. S. Al-Degs; G. M. Walker; M. Khraisheh (pp. 2157-2164).
The dielectric properties of pharmaceutical powder–(paracetamol, aspirin, lactose, maize starch, adipic acid) solvent (water) mixtures were measured at 2,450 MHz at a range of moisture contents (0–1.0 kg kg−1, dry basis) and temperatures (20–70 °C). The dielectric constant (ε′), loss factor (ε″) and penetration depth (d p) were found to be dependent on frequency, moisture content, temperature and powder type. For powder–water mixtures, a linear increase in the dielectric properties with moisture content was observed, whilst the temperature dependence was of quadratic form. The penetration depth was also significantly affected by temperature and moisture content. Although, ε″ also increased with increasing temperature, variation with moisture content was temperature dependent. This information on dielectric properties is essential for mathematical description of the pharmaceutical product temperature history during microwave heating and for the design of microwave drying equipment.

Keywords: Dielectric constant; Loss factor; Microwave; Penetration depth; Pharmaceutical; Powders

Analytical study on irradiated methylxanthine derivatives by Barbara Marciniec; Maciej Stawny; Karol Olszewski; Maciej Kozak; Marek Naskrent (pp. 2165-2170).
The effect of ionising radiation on the physico-chemical properties of three derivatives of xanthine: caffeine, theophylline and theobromine, has been studied. The above-drugs in the solid phase have been irradiated with E-beam of the energy 9.96 MeV with the doses varied from 25 to 400 kGy. The effects of the irradiation have been examined by differential scanning calorimetry (DSC), electron paramagnetic resonance (EPR) and high-performance liquid chromatography (HPLC). The results have shown that the methylxanthine derivatives studied are resistant to ionising irradiation in the doses usually used for sterilisation (<50 kGy), which means that they are relatively radiochemically stable and can be sterilised by irradiation.

Keywords: Radiation sterilization; Caffeine; Theophylline; Theobromine

Polymorphism and melt crystallisation of racemic betaxolol, a β-adrenergic antagonist drug by Teresa M. R. Maria; Ricardo A. E. Castro; M. Ramos Silva; M. Luísa Ramos; Licínia L. G. Justino; Hugh D. Burrows; João Canotilho; M. Ermelinda S. Eusébio (pp. 2171-2178).
We report the polymorphic behaviour, in melt cooling experiments, of racemic betaxolol, a low aqueous solubility selective β1-adrenergic antagonist drug with a flexible molecular structure. A multidisciplinary approach is employed, using thermal analysis (differential scanning calorimetry, polarised light thermomicroscopy), spectroscopic methods (infrared spectroscopy, magic angle spinning 1H NMR) and X-ray powder diffraction. A glass phase is obtained, T g ~ −10 °C, on cooling the melt, unless the cooling rate is ≤0.5 °C min−1, while a new metastable form, polymorph II, T fus = 33 °C, is generated in subsequent heating runs in a two step process. Although either partial crystallisation from the melt in the first step or the formation of an intermediate, metastable, low ordered phase may explain these observations, our results favour the second hypothesis. The stable polymorph I, T fus = 69 °C, which crystallizes on further heating after form II melting, has also been obtained either from polymorph II or from the molten phase, on standing at 25 °C. The racemic betaxolol crystalline phases are found to exhibit some degree of disorder.

Keywords: Betaxolol; Phase transition; Melt crystallisation; Polymorphism; Disordered crystal

Study of stability and drug-excipient compatibility of diethylcarbamazine citrate by Luíse L. Chaves; Larissa A. Rolim; Maria L. C. M. Gonçalves; Alexandre C. C. Vieira; Lariza D. S. Alves; Monica F. R. Soares; José L. Soares-Sobrinho; Maria C. A. Lima; Pedro J. Rolim-Neto (pp. 2179-2186).
Diethylcarbamazine citrate (DEC) is the main drug used in the lymphatic filariasis treatment. This study aimed to evaluate drug-excipient compatibility of binary mixtures (BMs) (1:1, w/w), initially by differential scanning calorimetry (DSC), and subsequently, if there were any interaction evidence, by complementary techniques, such as thermogravimetric (TG), non-isothermal kinetics, Fourier transform infrared (FT-IR), and X-ray diffraction (XRD). For the analyses of the BMs by DSC, we selected those with Tabletose®, representing the excipients containing lactose, polivinilpirrolidona (PVP), and magnesium stearate (MgS). The additional analyses by FT-IR and XRD showed no interaction evidence. The TG curves of DEC–Tabletose® showed no signs of interaction, unlike the TG curves of PVP and MgS, confirming the results of non-isothermal kinetics, in which the BMs with PVP and MgS decreased the reaction activation energy. Thus, it was concluded after evaluation that the excipients, especially the PVP and MgS, should be avoided.

Keywords: Thermal stability; Drug-excipient compatibility; Thermal analysis; Diethylcarbamazine citrate

Polymorphic effects at the eutectic melting in the H2O–glycine system by V. A. Drebushchak; A. G. Ogienko; Elena V. Boldyreva (pp. 2187-2194).
Solid mixtures of ice with three glycine polymorphs were heated up to the eutectic melting and the DSC has detected the eutectic temperatures of −2.8 °C for α-, −3.6 °C for β-, and −2.8 °C for γ-glycine. DSC peaks of the eutectic melting are rather strange in shape, indicating unclear processes in the solutions. Accurate DSC measurements of extremely small samples can probably provide us with the physicochemical tool for the investigation of polymorphic differences among different solutions. This may be important in relation to different bioavailability of solutions prepared from different polymorphs. Eutectic temperature of −4.7 °C in water–glycine system allows us to suggest that the unknown polymorph of glycine exists.

Keywords: DSC; Eutectic melting; Eutectic temperature; Glycine; Polymorphism; Water

Fast-scan vs conventional differential scanning calorimetry (DSC) techniques in detection of crystallization events of tolbutamide–polyethylene glycol composite by N. Musa; T. W. Wong (pp. 2195-2202).
This study investigated the capacity of fast-scan (400 °C min−1) against conventional (10 °C min−1) differential scanning calorimetry (DSC) techniques to track crystallization phenomenon in tolbutamide–polyethylene glycol 3000 composites prepared by hot melt method (mass ratios 1:1, 1:5, and 1:9) and stored at 25 and 75 % relative humidities. Drug crystallization in composites was indicated by X-ray diffractometry (XRD) and scanning electron microscopy characterization over 40 days storage. With reference to XRD as gold measurement standard, fast-scan DSC could not map the crystallization events of composites (Pearson correlation: fast-scan DSC peak temperature and enthalpy versus XRD peak intensity and area, p > 0.05). Conventional DSC was able to indicate marked drug crystallization through an increase in endothermic enthalpy value of peaks at high temperature regimes between 250 and 360 °C due to formation of high melting point crystal form.

Keywords: Crystallization; DSC; Polyethylene glycol; Tolbutamide

Effect of fractional crystallization on composition and thermal characteristics of avocado (Persea americana) butter by N. A. M. Yanty; J. M. N. Marikkar; Y. B. Che Man (pp. 2203-2209).
Fractionation of plant butters like avocado (Persea americana) may yield useful fat derivatives with distinct physical and functional properties. In this study, avocado butter was sequentially crystallized in acetone at 5 °C (2 h), 0 °C (24 h), and −20 °C (24 h) until the mother-liquor becomes devoid of any crystal formation. The high-melting stearin isolated at 5 °C and low-melting olein isolated at −20 °C were compared with the original sample in terms of fatty acid and triacylglycerol (TAG) compositions and thermal profiles. With respect to the original sample, low-melting olein is possessed with higher proportions of diunsaturated and triunsaturated TAG while high-melting stearin is found to become enriched with disaturated and trisaturated TAG molecules. These differences in compositions make the basic physico-chemical parameters as well as the thermal profiles of high-melting stearin and low-melting olein to be distinctly different from those of the original sample.

Keywords: Avocado butter; Fractional crystallization; Differential scanning calorimetry (DSC)

Structural, physico-chemical, thermal and pasting properties of potato (Solanum tuberosum L.) flour by Carolina Lopes Leivas; Fernanda Janaína Oliveira Gomes da Costa; Rafael Ramirez de Almeida; Renato João Sossela de Freitas; Sônia Cachoeira Stertz; Egon Schnitzler (pp. 2211-2216).
In this work, two varieties of potato flour (Ágata and IAPAR Cristina) were studied by simultaneous thermogravimetry–differential thermal analysis (TG–DTA), differential scanning calorimetry (DSC), rapid viscoamylographic analysis (RVA), and microscopy (NC-AFM) that were compared with conventional physico-chemical analysis, according different granulometry of each flour. Flours of IAPAR Cristina showed higher levels of starch, fiber, and phosphate and it showed higher thermal stability (TG–DTA), as well as higher pasting temperature and viscosity (RVA), and lower enthalpy of gelatinization (DSC) in the two granulometries. Flours of Agata showed higher gelatinization enthalpy (DSC) and lower pasting temperature (RVA). Atomic force microscopy—non contact method (NC-AFM), was important to check for protrusions and pores of the flour surfaces. The differences between cultivars can be attributed mainly to the genotypes and growth conditions of the tubers, which can modify the flour properties.

Keywords: Potato flour; Starch; Gelatinization; DSC; Pasting properties

Thermal, rheological, and structural behaviors of natural and modified cassava starch granules, with sodium hypochlorite solutions by Cleoci Beninca; Tiago André Denck Colman; Luiz Gustavo Lacerda; Marco Aurélio da Silva Carvalho Filho; Ivo Mottin Demiate; Gilbert Bannach; Egon Schnitzler (pp. 2217-2222).
The use of chemically modified starches is widely accepted in various industries, with several applications. In this research, natural cassava starch granules were treated with standard sodium hypochlorite solution at 0.8, 2.0, and 5.0 g Cl/100 g starch. The native and modified starch samples were investigated by means of the following techniques: simultaneous thermogravimetry–differential thermal analysis, which allowed us to verify the thermal decomposition associated with endothermic or exothermic phenomena; and differential scanning calorimetry that was used to determine gelatinization enthalpy as well as the rapid viscoamylographic analysis that provided the pasting temperature and viscosity. By means of non-contact-atomic force microscopy method and X-ray powder patterns diffractometry, it was possible to observe the surface morphology, topography of starch granules, and alterations in the granules’ crystallinity.

Keywords: Cassava starch; Thermal analysis; Gelatinization; Enthalpy; Oxidized starch

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