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Analytica Chimica Acta (v.647, #1)
Determination of HIV drugs in biological matrices: A review by Antonio Checa; Ramon Oliver; Santiago Hernández-Cassou; Javier Saurina (pp. 1-13).
The present paper reviews the recent advances on the determination of antiretroviral drugs against the human immunodeficiency virus (HIV). Methods have been reviewed with special emphasis on the principal analytical strategies for dealing with clinical samples as well as the determination of the newest drugs. The most critical steps of the analytical procedures including the sample treatment, separation and validation have been discussed. Finally, a brief description of representative applications is given.
Keywords: Antiretroviral drugs; Biological matrices; High-performance liquid chromatography; Ultraviolet detection; Mass spectrometry/mass spectrometry detection; Validation
Review: Bioanalytical applications of biomolecule-functionalized nanometer-sized doped silica particles by Dietmar Knopp; Dianping Tang; Reinhard Niessner (pp. 14-30).
Recent research has looked to develop innovative and powerful novel biofunctionalized nanometer-sized silica particles, controlling and tailoring their properties in a very predictable manner to meet the needs of specific applications. The silica shells of these particles facilitate a wide variety of surface reactions and allow conjugation with biomolecules like proteins and DNA. There exist a multitude of possible applications of fabricated nanoparticles in biotechnology and medicine. In particular, they have proved to be highly useful for biosensing, assay labelling, bioimaging, and in research on a variety of molecular tags in cellular and molecular biology. Techniques commonly rely on the use of silica-coated semiconductor quantum dots, organic dyes, magnetic particles, and Raman active particles. Inorganic-biological hybrid particles combine the properties of both materials, i.e., the spectroscopic characteristics of the entrapped nanocrystal, and the biomolecular function of the conjugated entity. Rather than being exhaustive, this review focuses on selected examples to illustrate novel concepts and promising applications. Approaches described include the encoding of silica nanoparticles with different groups, and conjugation with various biological entities. Further, promising applications in bioanalysis are considered and discussed.
Keywords: Silica nanoparticles; Bioconjugation; Bio-barcode; Biomolecules; Encapsulated molecular tags; Bioanalysis
Tutorial: The modelling of chemical processes by Nichola McCann; Marcel Maeder (pp. 31-39).
The modelling of chemical processes entails the computation of the concentration profiles of all reaction species as a function of the reaction time. The basis for the calculations is the system of differential equations (ODE's) that is defined by the reaction mechanism. Most textbooks on chemical kinetics concentrate on those few reaction mechanisms that lead to ODE's with explicit solutions. In this tutorial, we demonstrate that numerical integration is a viable alternative, that it can be applied to any mechanism, and that it is easy to do so. Matlab example programs illustrate the concepts and they allow the reader to explore the effects of changing conditions such as initial concentrations or rate constants etc. Example reaction mechanisms include a zero-th order enzymatic reaction and reactions at non-constant temperature and pH.
Keywords: Modeling; Chemical processes; Reaction mechanism; Numerical integration; ODE solver
Fermentation condition outweighed truffle species in affecting volatile organic compounds analyzed by chromatographic fingerprint system by Ya-Jie Tang; Guan Wang; Yuan-Yuan Li; Jian-Jiang Zhong (pp. 40-45).
The influences of fermentation conditions and truffle species (i.e., Tuber melanosporum, Tuber sinense, Tuber indicum, and Tuber aestivum) on the volatile organic compounds (VOCs) originated from truffle fermentation mycelia were studied by using chromatographic fingerprint system for the first time. Gas chromatography combined with statistical methods including similarity analysis and hierarchical cluster analysis was applied to develop chromatographic fingerprint system for truffle VOCs evaluation. Fermentation conditions affected the VOCs from truffle fermentation mycelia much more significantly than truffle species. This indicated that it is possible to adjust the aroma of truffle fermentation mycelia similar with the natural fruiting-body through the control of fermentation process.
Keywords: Truffle fermentation mycelia; Volatile organic compounds; Aroma; Fingerprints; Species; Fermentation conditions
Two-dimensional wavelet analysis based classification of gas chromatogram differential mobility spectrometry signals by Weixiang Zhao; Shankar Sankaran; Ana M. Ibáñez; Abhaya M. Dandekar; Cristina E. Davis (pp. 46-53).
This study introduces two-dimensional (2-D) wavelet analysis to the classification of gas chromatogram differential mobility spectrometry (GC/DMS) data which are composed of retention time, compensation voltage, and corresponding intensities. One reported method to process such large data sets is to convert 2-D signals to 1-D signals by summing intensities either across retention time or compensation voltage, but it can lose important signal information in one data dimension. A 2-D wavelet analysis approach keeps the 2-D structure of original signals, while significantly reducing data size. We applied this feature extraction method to 2-D GC/DMS signals measured from control and disordered fruit and then employed two typical classification algorithms to testify the effects of the resultant features on chemical pattern recognition. Yielding a 93.3% accuracy of separating data from control and disordered fruit samples, 2-D wavelet analysis not only proves its feasibility to extract feature from original 2-D signals but also shows its superiority over the conventional feature extraction methods including converting 2-D to 1-D and selecting distinguishable pixels from training set. Furthermore, this process does not require coupling with specific pattern recognition methods, which may help ensure wide applications of this method to 2-D spectrometry data.
Keywords: Wavelet; Principal component; Support vector machine; Pattern recognition; Gas chromatography; Differential mobility spectrometry
Analysis of the factors that significantly influence the stability of fluoroquinolone–metal complexes by Bartosz Urbaniak; Zenon J. Kokot (pp. 54-59).
The aim of the present study was to evaluate factors contributing to the differences between the overall stability constants (log β pqr) of the fluoroquinolone–metal ion complexes.The experiments were performed using potentiometric titration method in wide pH range. The overall stability constants (log β pqr) were determined using the Hyperquad program. Complexation equilibria of eight different fluoroquinolones with six divalent and trivalent metal ions were investigated in this study.The authors employed a multifactorial ANOVA analysis, fixed effect model to describe the influence of particular variables affecting the stability of the analyzed complex species. Four different variables were set at different levels labeled. The ligand number (LF) was the first factor. LF determined the number of fluorochinolone molecules in the complex structure, and could take the values 1, 2 or 3. The second factor (Me) was connected with the type of the metal ion bonded in the complex. Since six different metal cations were studied, the Me factor was described with six levels. The number of hydrogen or hydroxide groups substituted into the complex molecule was the third variable (HR) with many levels labeled: q, a, s, d, f and g. The last factor FQ described the type of the fluorochinolone used for complex formations. All variables analyzed here were statistically significant ( p value lower than 0.01), which indicates that all of them strongly affect the log β pqr value. Binary interactions (LF–Me, LF–FQ, Me–HR and Me–FQ) between variables were also stated, which suggests that the effects of these variables were higher than we could calculate based on the effect of each variable alone.The ANOVA analysis has shown that the following factors Me, LF and HR were the most important for the stability of the fluoroquinolone–metal ion complexes. It was also found that according to the FQ factor (type of ligand molecule) all analyzed fluoroquinolones formed stable complexes with metals. It was proved that the application of ANOVA for the entire complexation profile of analyzed fluoroquinolones with polyvalent metal ions was a valid technique for detecting the statistically significant differences in the complexation profiles. Such information may be very useful for better understanding and interpretation of differences in bioavailability of fluoroquinolones and their interactions with antacids and other multimineral drugs.
Keywords: Fluoroquinolones–metal ion complexes; Stability constants; Multifactorial analysis of variance analysis; Fixed-effect model
Fabrication of a new electrochemiluminescent sensor for fentanyl citrate based on glassy carbon microspheres and ionic liquid composite paste electrode by Hong Dai; Huifeng Xu; Xiaoping Wu; Yuwu Chi; Guonan Chen (pp. 60-65).
Due to the high performance of glassy carbon in the aspects of mechanical strength, electrical conductivity and high corrosion resistance, etc., glassy carbon has been widely used in the electrochemistry. A new form of glassy carbon, glassy carbon microsphere, was utilized to couple with ionic liquid in preparing a new electrochemiluminescent platform for Ru(bpy)3Cl2. Room temperature ionic liquid has been proposed to be very interesting and efficient pasting binder to replace the non conductive organic binders for the fabrication of composite paste electrode. Attributed to the special characteristics of glassy carbon microspheres and room temperature ionic liquid [N-octylpyridium tetrafluoroborate (OPFP)], this new electrochemiluminescent sensor exhibited excellent electrochemiluminescent performance in Ru(bpy)32+ solution. We first found that fentanyl citrate could increase the ECL of Ru(bpy)32+, hence an ECL approach was developed for the determination of fentanyl citrate based on this glassy carbon microspheres based electrochemiluminescent platform with high sensitivity. Under the optimized conditions, the enhanced electrochemiluminescent intensity versus fentanyl citrate concentration was linear in the range of 1.0×10−8 to 1.0×10−4molL−1 with a detection limit of 8.5×10−9molL−1, and the relative standard deviation for 1.0×10−6molL−1 fentanyl citrate was 1.90% ( n=10). This protocol has extended the application scopes of glassy carbon material and promoted the application of glassy carbon microspheres in electroanalysis.
Keywords: Electrochemiluminescence; Glassy carbon microsphere; N-octylpyridium tetrafluoroborate; Ru(bpy); 3; Cl; 2; Fentanyl citrate
Comparative studies of neodymium (III)-selective PVC membrane sensors by Vinod K. Gupta; Rajendra N. Goyal; Ram A. Sharma (pp. 66-71).
Sensors based on two neutral ionophores, N,N′-bis((1H-pyrrol-2-yl)methylene)cyclohexane-1,2-diamine (L1) and 3,3′-(cyclohexane-1,2-diylbis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)bis(5-hydroxymethyl)pyridine-2-ol) (L2) are described for quantification of neodymium (III). Effect of various plasticizers; 2-nitrophenyloctylether ( o-NPOE), dibutyl butylphosphonate (DBBP), tri-n-butyl phosphates (TBP), dioctylpthalate (DOP) and chloronapthalen (CN) and anion excluder, sodiumtetraphenylborate (NaTPB) has been studied. The membrane composition of PVC: o-NPOE:ionophore (L1):NaTPB (w/w; mg) of 150:300:5:5 exhibited best performance. The sensor with ionophore (L1) exhibits significantly enhanced selectivity towards neodymium (III) in the concentration range 5.0×10−7 to 1.0×10−2M with a detection limit of 1.0×10−7M and a Nernstian compliance (19.8±0.3mVdecade−1 of activity) within pH range 4.0–8.0. The response time of sensor was found as 10s. The influence of the membrane composition and possible interfering ions has also been investigated on the response properties of the electrode. The fast and stable response, good reproducibility and long-term stability of the sensor are observed. The sensor has been found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol or acetonitrile and could be used for a period of 3 months. The selectivity coefficients determined by using fixed interference method (FIM) indicate high selectivity for neodymium. The proposed electrode shows fairly good discrimination of neodymium (III) from other cations. The application of prepared sensor has been demonstrated in the determination of neodymium (III) in spiked water samples.
Keywords: Ion-selective electrode; Neodymium ion; Schiff base; Poly(vinyl chloride) membranes
Ultrasonic nebulization extraction coupled with headspace single drop microextraction and gas chromatography–mass spectrometry for analysis of the essential oil in Cuminum cyminum L. by Lu Wang; Ziming Wang; Huihui Zhang; Xueyuan Li; Hanqi Zhang (pp. 72-77).
A novel method for analysis of essential oil in Cuminum cyminum L. using simultaneous ultrasonic nebulization extraction and headspace single drop microextraction (UNE–HS-SDME) followed by gas chromatography–mass spectrometry was developed. Experimental parameters, including the kind of suspended solvent, microdrop volume, sample amount, extraction time, enrichment time and salt concentration were examined and optimized. Compared with hydrodistillation (HD), UNE–HS-SDME provides the advantages of a small amount of sample (50mg), time-saving (20min), simplicity, cheapness and low toxicity. In addition, UNE–HS-SDME also provided higher enrichment efficiency and sensitivity compared with stirring extraction (SE)–HS-SDME, ultrasonic assistant extraction (UAE) and UNE. Some constituents in the essential oil, were identified and the detection limits for β-pinene, p-cymene and γ-terpinene range from 6.67pLL−1 to 14.8pLL−1. The results indicated that the UNE–HS-SDME is simple and highly efficient extraction and enrichment technique.
Keywords: Cuminum cyminum; L.; Ultrasonic nebulization extraction; Headspace single drop microextraction; Essential oil; Gas chromatography–mass spectrometry
Portable microfluidic system for determination of urinary creatinine by Temsiri Songjaroen; Thitima Maturos; Aussawapong Sappat; Adisorn Tuantranont; Wanida Laiwattanapaisal (pp. 78-83).
A simple, low cost and portable microfluidic system based on a two-point alkaline picrate kinetic reaction has been developed for the determination of urinary creatinine. The creatinine reacts with picric acid under alkaline conditions, forming an orange-red colour, which is monitored on PDMS microchip using a portable miniature fibre optic spectrometer at 510nm. A linear range was displayed from 0 to 40mgL−1 creatinine ( r2=0.997) with a detection limit of 3.3mgL−1 (S/N=3). On-chip absorbance signals are reproducible, with relative standard deviations (RSDs) of 7.1%, when evaluated with 20mgL−1 creatinine ( n=10). The standard curves in which the intra-run CVs (4.7–6.8%) and inter-run CVs (7.9%) obtained were performed on three different days and exhibited good reproducibility. The method was highly correlated with the conventional spectrophotometric method when real urine samples were evaluated ( r 2 =0.948 ; n=15).
Keywords: Creatinine determination; Microfluidic system; Poly(dimethylsiloxane); Jaffé reaction; On-chip absorbance detection
Dual optoelectronic visual detection and quantification of spectroscopically silent heavy metal toxins: A multi-measurand sensing strategy based on Rhodamine 6G as chromo or fluoro ionophore by K.P. Prathish; D. James; J. Jaisy; T. Prasada Rao (pp. 84-89).
A novel colorimetric chemo-sensor for the simultaneous visual detection and quantification of spectroscopically silent heavy metal toxins viz. cadmium, lead and mercury has been developed. This is based on the proposed sequential ligand exchange (SLE) mechanism of iodide from Pb–I−–Rhodamine 6G ion associate with citrate (without affecting ion associates of Cd and Hg) and subsequently from Cd–I−–Rhodamine 6G ion associate with EDTA (without affecting Hg–I−–Rhodamine 6G). Multi-measurand detection and quantification by colorimetry is possible as the individual toxins gives identical bathochromic shifts in aqueous solution, i.e. from 530 to 575nm on formation of ternary ion associates in singular, binary and ternary mixtures. The visual detection provides a simple, quick and sensitive detection method in addition to quantification via spectrophotometry with Sandell sensitivities of 1.1, 15 and 2.5μgdm−2 for cadmium, lead and mercury, respectively. The developed procedure has been successfully tested for the analysis of environmental (cast alkali, lead acid battery and zinc manufacturing industry effluents) samples. Furthermore, the multi-measurand quantification of the above-mentioned heavy metal toxins based on fluorescence quenching and use of Pyronine G as chromo-ionophore instead of Rhodamine 6G is also described.
Keywords: Multi-measurand detection and quantification; Chemo-sensor; Heavy metal toxins; Sequential ligand exchange; Natural waters; Industrial effluents
Production and characterization of a broad-specificity polyclonal antibody for O, O-diethyl organophosphorus pesticides and a quantitative structure–activity relationship study of antibody recognition by Zhen-Lin Xu; Gui-Mian Xie; Yong-Xiang Li; Bing-Feng Wang; Ross C. Beier; Hong-Tao Lei; Hong Wang; Yu-Dong Shen; Yuan-Ming Sun (pp. 90-96).
Polyclonal antibody (PAb) with broad-specificity for O, O-diethyl organophosphorus pesticides (OPs) against a generic hapten, 4-(diethoxyphosphorothioyloxy)benzoic acid, was produced. The obtained PAb showed high sensitivity to seven commonly used O, O-diethyl OPs in a competitive indirect enzyme-linked immunosorbent assay (ciELISA) using a heterologous coating antigen, 4-(3-(diethoxyphosphorothioyloxy)phenylamino)-4-oxobutanoic acid. The 50% inhibition value (IC50) was 348ngmL−1 for parathion, 13ngmL−1 for coumaphos, 22ngmL−1 for quinalphos, 35ngmL−1 for triazophos, 751ngmL−1 for phorate, 850ngmL−1 for dichlofenthion, and 1301ngmL−1 for phoxim. The limit of detection (LOD) met the ideal detection criteria of all the seven OP residues. A quantitative structure–activity relationship (QSAR) model was constructed to study the mechanism of antibody recognition using multiple linear regression analysis. The results indicated that the frontier-orbital energies (energy of the highest occupied molecular orbital, EHOMO, and energy of the lowest unoccupied molecular orbital, ELUMO) and hydrophobicity (log of the octanol/water partition coefficient, log P) were mainly responsible for the antibody recognition. The linear equation was log(IC50)=−63.274 EHOMO+15.985 ELUMO+0.556log P−25.015, with a determination coefficient ( r2) of 0.908.
Keywords: Antibody recognition; Broad-specificity; Heterologous assay; Organophosphorus pesticides; Quantitative structure–activity relationship
Simultaneous determination of epinephrine, uric acid and xanthine in the presence of ascorbic acid using an ultrathin polymer film of 5-amino-1,3,4-thiadiazole-2-thiol modified electrode by Palraj Kalimuthu; S. Abraham John (pp. 97-103).
This paper describes the simultaneous determination of epinephrine (EP), uric acid (UA) and xanthine (XN) in the presence of ascorbic acid (AA) using electropolymerized ultrathin film of 5-amino-1,3,4-thiadiazole-2-thiol (p-ATT) modified glassy carbon (GC) electrode in 0.2M phosphate buffer solution (pH 5). Although bare GC electrode resolves the voltammetric signals of AA and XN, it fails to resolve the voltammetric signals of EP and UA in a mixture. However, the p-ATT modified electrode not only separates the voltammetric signals of AA, EP, UA and XN with potential difference of 150, 120 and 400mV between AA-EP, EP-UA and UA-XN, respectively but also shows higher oxidation current for these molecules. The p-ATT modified electrode exhibits excellent selectivity towards the oxidation of EP, UA and XN in the presence of 40-fold higher concentration of AA. Further, the p-ATT modified electrode was also used for the selective determination of EP in the presence of 40-fold higher concentrations of AA, UA and XN. Using amperometric method, we achieved the lowest detection of 40nM EP and 60nM each UA and XN. The amperometric current response was increased linearly with increasing EP concentration in the range of 4.0×10−8 to 4.0×10−5M and the detection limit was found to be 27×10−11M (S/N=3). The practical application of the present modified electrode was demonstrated by determining the concentration of EP in epinephrine tartrate injection and XN in human urine samples.
Keywords: Electropolymerization; Chemically modified electrodes; Ascorbic acid; Epinephrine; Uric acid; Xanthine
Combination of off-line solid-phase extraction and on-column sample stacking for sensitive determination of parabens and p-hydroxybenzoic acid in waters by non-aqueous capillary electrophoresis by Eva Blanco; María del Carmen Casais; María del Carmen Mejuto; Rafael Cela (pp. 104-111).
For the first time, a procedure based on solid-phase extraction (SPE) for the simultaneous extraction of a group of parabens (methyl, ethyl, propyl, butyl and benzyl p-hydroxybenzoates) and p-hydroxybenzoic acid (PHBA), from environmental water samples has been developed. Analysis of the extracts was performed by non-aqueous capillary electrophoresis (NACE) coupled with diode array detection (DAD), using large-volume sample stacking (LVSS) based on the electroosmotic flow pump as on-column preconcentration technique. Several water samples, such as tap, river, and wastewater samples, were analyzed using both SPE–NACE–DAD and SPE–LVSS–NACE–DAD methods. It has been observed that in addition to SPE parameters such as sorbent material, sample pH, breakthrough volume, addition of an organic solvent and elution solvent, also sample characteristics, such as organic matter content, have influence on SPE extraction yields, especially in the case of PHBA. The presence of PHBA and some parabens was detected at trace levels in surface water samples. Concentrations up to 8.4ngmL−1 were found in raw wastewater, with the highest levels corresponding to methylparaben, propylparaben, and their main degradation product, PHBA.
Keywords: Large-volume sample stacking; Non-aqueous capillary electrophoresis; Parabens; p; -Hydroxybenzoic acid; Solid-phase extraction; Water samples
Microvolume turbidimetry for rapid and sensitive determination of the acid labile sulfide fraction in waters after headspace single-drop microextraction with in situ generation of volatile hydrogen sulfide by I. Lavilla; F. Pena-Pereira; S. Gil; M. Costas; C. Bendicho (pp. 112-116).
In this work, we demonstrate the feasibility of applying headspace single-drop microextraction with in-drop precipitation for the quantitative determination of the acid labile sulfide fraction (H2S, HS−, and S2− (free sulfide), amorphous FeS and some metal sulfide complexes–clusters as ZnS) in aqueous samples by microvolume turbidimetry. The methodology lies in the in situ hydrogen sulfide generation and subsequent sequestration into an alkaline microdrop containing ZnO22− and exposed to the headspace above the stirred aqueous sample. The ZnS formed in the drop was then determined by microvolume turbidimetry. The optimum experimental conditions of the proposed method were: 2μL of a microdrop containing 750mgL−1 Zn(II) in 1molL−1 NaOH exposed to the headspace of a 20-mL aqueous sample stirred at 1600rpm during 80s after derivatization with 1mL of 6molL−1 HCl. An enrichment factor of 1710 was achieved in only 80s. The calibration graph was linear in the range of 5–100μgL−1 with a detection limit of 0.5μgL−1. The repeatability, expressed as relative standard deviation, was 5.8% ( N=9). Finally, the proposed methodology was successfully applied to the determination of the acid labile sulfide fraction in different natural water samples.
Keywords: Microvolume turbidimetry; Single-drop microextraction; Sulfide; Water analysis
Development of a model for the rational design of molecular imprinted polymer: Computational approach for combined molecular dynamics/quantum mechanics calculations by Cunku Dong; Xin Li; Zechong Guo; Jingyao Qi (pp. 117-124).
A new rational approach for the preparation of molecularly imprinted polymer (MIP) based on the combination of molecular dynamics (MD) simulations and quantum mechanics (QM) calculations is described in this work. Before performing molecular modeling, a virtual library of functional monomers was created containing forty frequently used monomers. The MD simulations were first conducted to screen the top three monomers from virtual library in each porogen–acetonitrile, chloroform and carbon tetrachloride. QM simulations were then performed with an aim to select the optimum monomer and progen solvent in which the QM simulations were carried out; the monomers giving the highest binding energies were chosen as the candidate to prepare MIP in its corresponding solvent. The acetochlor, a widely used herbicide, was chosen as the target analyte. According to the theoretical calculation results, the MIP with acetochlor as template was prepared by emulsion polymerization method using N,N-methylene bisacrylamide (MBAAM) as functional monomer and divinylbenzene (DVB) as cross-linker in chloroform. The synthesized MIP was then tested by equilibrium-adsorption method, and the MIP demonstrated high removal efficiency to the acetochlor. Mulliken charge distribution and1H NMR spectroscopy of the synthesized MIP provided insight on the nature of recognition during the imprinting process probing the governing interactions for selective binding site formation at a molecular level. We think the computer simulation method first proposed in this paper is a novel and reliable method for the design and synthesis of MIP.
Keywords: Molecular imprinted polymer; Molecular dynamics; Density functional theory; Acetochlor