Analytical and Bioanalytical Chemistry (v.375, #8)
PCR technology for screening and quantification of genetically modified organisms (GMOs)
by Arne Holst-Jensen; Sissel B. Rønning; Astrid Løvseth; Knut G. Berdal (pp. 985-993).
Although PCR technology has obvious limitations, the potentially high degree of sensitivity and specificity explains why it has been the first choice of most analytical laboratories interested in detection of genetically modified (GM) organisms (GMOs) and derived materials. Because the products that laboratories receive for analysis are often processed and refined, the quality and quantity of target analyte (e.g. protein or DNA) frequently challenges the sensitivity of any detection method. Among the currently available methods, PCR methods are generally accepted as the most sensitive and reliable methods for detection of GM-derived material in routine applications.The choice of target sequence motif is the single most important factor controlling the specificity of the PCR method. The target sequence is normally a part of the modified gene construct, for example a promoter, a terminator, a gene, or a junction between two of these elements. However, the elements may originate from wildtype organisms, they may be present in more than one GMO, and their copy number may also vary from one GMO to another. They may even be combined in a similar way in more than one GMO. Thus, the choice of method should fit the purpose. Recent developments include event-specific methods, particularly useful for identification and quantification of GM content. Thresholds for labelling are now in place in many countries including those in the European Union. The success of the labelling schemes is dependent upon the efficiency with which GM-derived material can be detected. We will present an overview of currently available PCR methods for screening and quantification of GM-derived DNA, and discuss their applicability and limitations. In addition, we will discuss some of the major challenges related to determination of the limits of detection (LOD) and quantification (LOQ), and to validation of methods.
Keywords: Event-specific Validation Detection and quantification limit Real-time PCR Multiplex PCR Reference materials
A combinatorial approach to obtain affinity media with binding properties towards the aflatoxins
by Cinzia Tozzi; Laura Anfossi; Claudio Baggiani; Cristina Giovannoli; Gianfranco Giraudi (pp. 994-999).
In our work we performed a combinatorial solid-phase synthesis in aqueous medium to prepare peptide libraries from which to select an amino acid sequence with binding properties towards aflatoxins.We used polystyrene beads, functionalised with carboxylic groups as solid support and eight amino acids as monomers. During the first step 64 different sequences of two amino acids were prepared by exploiting the principles of combinatorial chemistry; then the binding properties of all sequences towards aflatoxin B1 were checked. We determined binding constants towards aflatoxin B1 and towards aflatoxins B2, G1 and G2. Results were promising, so we prepared a new library by using the selected dipeptide as the starting solid phase. After selecting the best tetrapeptide sequences, we determined binding constants towards the quoted aflatoxins. We obtained binding constants (K>104 M−1) similar to those shown by human serum albumin for similar compounds. Preliminary studies on an extraction column were promising for the development of an SPE system and for its application in food matrices.
Keywords: Amino acid Aflatoxins Combinatorial libraries Binding properties Affinity column
Molecular heterogeneity, detected by two electrophoretic micro procedures, of IgG in human cerebrospinal fluid (CSF)
by T. O. Kleine; T. Damm (pp. 1000-1005).
Semi-automated electrophoretic procedures in the PhastSystem (Amersham Pharmacia Biotech) with micro polyacrylamide gels (PAGs) and SDS–PAG gradients were modified to analyze IgG in human cerebrospinal fluid (CSF) and matched serum samples with respect to the molecular IgG structure L-H-H-L. Isoelectric focusing (IEF) with specific immunofixation detected discrete IgG bands in CSF standing out against a polyclonal and monoclonal background pattern in CSF and serum; they were denoted oligoclonal bands (IgG OBs) (OB assay positive) indicating IgG synthesis in the central nervous system (CNS) of patients with subacute and chronic processes of inflammatory CNS disorders; assay was negative with identical (mirror) bands in CSF and serum for other CNS processes. IgG OBs were specified as lambda (kappa) IgG subfractions, precipitated with the anti-light (L) chains lambda (kappa) and anti-heavy (H) chain fragments (Fd, Fc, CH2) as well as with anti-F(ab′)2, and as duplex IgGs with kappa and lambda OBs at the same pI. With SDS–PAG gradient electrophoresis and specific immunofixation more than six IgG fractions were detected and classed according to apparent molecular weights of a S-sulfonated human IgG standard; they were characterized with the monospecific antibodies against the L and H chain fragments as 25, 50, 75, 100, 125 and 150 kD fractions containing combinations of L and H chains as well as mixtures of both L and H chain fragments of varying dimensions. Generally, this molecular IgG heterogeneity could not be connected with the IgG OB heterogeneity revealed by IEF; but single OBs in the strongly alkaline pH region of PAG may correspond to H fragments with basic pI. Nevertheless, evidence for the existence of both free L chains and the free H chain were revealed as specific OBs with IEF and with the anti-L and anti-H antibodies in the 25 kD and 50 kD fractions, respectively, of CSF samples of six patients with diverse CNS diseases. Further experiments are needed to elicit the origin of the molecular IgG heterogeneity during the immune response of subacute and chronic inflammatory processes in human CNS.
Keywords: Oligoclonal bands Molecular IgG heterogeneitiy IgG subfractions Free light chains Free gamma chain fragments Cerebrospinal fluid
Comparison of potassium ion preference of potassium-sensing oligonucleotides, PSO-1 and PSO-2, carrying the human and Oxytricha telomeric sequence, respectively
by Shigeori Takenaka; Hiroyuki Ueyama; Takahiko Nojima; Makoto Takagi (pp. 1006-1010).
Human [G3(TTAG3)3] and Oxytricha [G4(T4G4)3] telomere model oligonucleotides, PSO-1 and PSO-2, bearing two fluorophores, 6-carboxyfluorescein (6-FAM) and 6-carboxytetramethylrhodamine (6-TAMRA) at their 5′- and 3′-termini, respectively, were synthesized. Both of them can form an intramolecular antiparallel tetraplex upon addition of K+, and an enhanced fluorescence resonance energy transfer (FRET) was observed. PSO-1 showed a 43,000 times higher selectivity for K+ against Na+. Fluorometric and circular dichroism spectrophotometric studies revealed that this system is useful for the evaluation of the interaction of different telomeric repeat oligonucleotide sequences with metal ions.
Keywords: Fluorescence resonance energy transfer (FRET) G-quartet Potassium-sensing oligonucleotide (PSO) Telomere Tetraplex
Determination of antioxidant properties of aromatic herbs, olives and fresh fruit using an enzymatic sensor
by L. Campanella; A. Bonanni; G. Favero; M. Tomassetti (pp. 1011-1016).
The aim was to experimentally evaluate the antioxidant capacity of different fresh aromatic herbs (field balm, marjoram, parsley, rosemary, sage, sweet basil), several varieties of olives from Central Italy ('Carboncello', 'Rosciolo', 'Olivastro', 'Coratello', 'Leccino', 'Frantoio') and several types of fresh fruit (apple, apricot, banana, cherry, fig, grape, medlar, melon, peach, pear, pineapple, plum, water melon, yellow plum) using a superoxide dismutase (SOD) biosensor developed by the present authors.Measurements were carried out by comparing the biosensor response to the concentration of superoxide radical produced in solution using a xanthine/xanthine oxidase system in the presence and absence of the antioxidant sample considered. Tests carried out on different samples of fruit and aromatic herbs showed that the homogenised samples had better antioxidant properties than the centrifuged ones (obtained by centrifuging the homogenate), which sometimes gave extremely low antioxidant capacity values.The reliability of the proposed method was checked by comparing the trend of some experimental results found using the SOD biosensor with those reported in the literature obtained using the classic (ORAC) method. The precision of this method of analysis was found to be good for samples of aromatic herbs (RSD% ≤8%), acceptable for homogenised fruit samples (RSD% ≤13%) and less good for homogenised and centrifuged samples (RSD% ≤20%).
Keywords: Antioxidant capacity Evaluation Superoxide dismutase Biosensor
Determination of 4- n -nonylphenol in water by enzyme immunoassay
by Jeanne V. Samsonova; Maya Yu. Rubtsova; Milan Franek (pp. 1017-1019).
A range of monoclonal antibody-based competitive immunoassays in the format of microtitre plate ELISA and dipstick tests for quantitative and semi-quantitative detection of 4- n -nonylphenol in water was developed. A simple visual dipstick test was based on changing of spot colour from green to brown in the presence of 4- n -nonylphenol at concentrations within the range 10–100 ng mL−1. Two different detection systems were used for quantitative immunoassay. Application of enhanced chemiluminescence (ECL) resulted in an increase of the sensitivity of ELISA when compared to conventional colorimetric detection. Thus a detection limit of 0.06 ng mL−1 of 4- n -nonylphenol was achieved with IC50 2.0 ng mL−1. The tests developed were applied to natural and spiked water samples.
Keywords: 4- n -Nonylphenol Enzyme immunoassay Membrane immunoassay Enhanced chemiluminescent reaction Water
Permanently oriented antibody immobilization for digoxin determination with a flow-through fluoroimmunosensor
by P Fernández; JS Durand; C Pérez-Conde; G Paniagua (pp. 1020-1023).
This paper reports a new flow-through fluoroimmunosensor, the function of which is based on antibodies immobilized on an inmunoreactor of controlled-pore glass (CPG), for determination of digoxin, used in the treatment of congestive heart failure and artery disease. The immunosensor has a detection limit of 1.20 μg L−1 and provides high reproducibility (RSD=4.5% for a concentration of 0.0025 mg L−1, and RSD=6.7% for 0.01 mg L−1). The optimum working concentration range was found to be 1.2×10−3–4.0×10−2 mg L−1. The lifetime of the immunosensor was about 50 immunoassays; if stored unused its lifetime can be extended to three months. A sample speed of about 10–12 samples per hour can be attained. Possible interference from substances with structures similar to digoxin (morphine, heroin, tebaine, codeine, pentazocine and narcotine) was investigated. No cross-reactivity was seen at the highest digoxin: interferent ratio studied (1:100). The proposed fluoroimmunosensor was successfully used to determine digoxin concentrations in human serum samples.
Keywords: Flow-through fluoroimmunosensor Digoxin Permanent immobilization
Comparison of the voltammetric studies at mercury and glassy carbon electrodes for the interaction of lumichrome with DNA and analytical applications
by M. S. Ibrahim; M. M. Kamal; Y. M. Temerk (pp. 1024-1030).
The determination of the interaction between lumichrome (LC), one of the products of decomposition of the biologically important flavins, and calf thymus double-stranded DNA was performed by using cyclic voltammetry (CV) and differential pulse stripping voltammetry (DPSV) in connection with a hanging mercury drop electrode (HMDE) or glassy carbon electrode (GCE). The nature of the process taking place at both electrode surfaces was clarified. It was found that the addition of DNA to a buffered LC solution results in the decrease of redox peak currents with changes in the peak potentials at both electrodes. We assume that LC interacting with DNA produces an electrochemically inactive supramolecular complex via intercalation. There was a difference between the electrochemical parameters determined at the HMDE and those at the GCE. The binding constants (K) of the LC–DNA complex at HMDE and GCE were determined through the changes of peak currents and their values at the 105 level and 104 level with each nucleotide residue of DNA binding one LC molecule, respectively. Furthermore, the calibration graph for the determination of DNA was obtained by the decrease in the DPSV peak current of LC in the presence of DNA. Different variables, such as the concentration of LC, the accumulation time and solution conditions, were studied and optimised to maximize the sensitivity; in addition, the detection limit and the reproducibility were determined.
Keywords: Voltammetry Lumichrome DNA HMDE GCE Interaction
Comparative study of coulometric and amperometric detection for the determination of macrolides in human urine using high-performance liquid chromatography
by Maria-José González de la Huebra; Guy Bordin; Adela R. Rodríguez (pp. 1031-1037).
A high-performance liquid chromatography (HPLC) method using chromatographic conditions optimised in a previous work was applied for the separation of three macrolide antibiotics roxithromycin (Rox), oleandomycin (Ole) and rosamicin (Ros) and further determination of two of them, roxithromycin (Rox) and oleandomycin (Ole), in human urine samples. A comparative study of the behaviour of these macrolides under the two types of electrochemical detection (EC) widely coupled with HPLC, that is coulometric (EC–C) and amperometric (EC–A), was carried out by applying the same multiresidue method. From the assays performed using both detectors the comparison was made taking relevant criteria such as detection limits, linearity, recovery and precision values into account. As a result of this comparison, the coulometric detector appears slightly more suitable than the amperometric one for macrolide analysis.
The use of thermal lensing for the determination of pyrogens
by N. V. Orlova; M. A. Proskurnin; V. A. Samburova; I. D. Dryagleva; A. V. Brusnichkin (pp. 1038-1044).
Based on the optimized spectrophotometric determination of pyrogens (of various classes (p-aminophenol and endotoxins), thermal lensing was applied to the determination of these substances at the submicrogram level. The limit of detection of p-aminophenol, a pyrogenic impurity in pharmaceutical formulations of paracetamol, by reaction with resorcinol in alkaline solutions is 100 ng mL–1. Phloroglucinol was considered as an analog of resorcinol as a reagent in this reaction. The conditions of spectrophotometric determination of pyrogenic lipopolysaccharides (endotoxins) by ion-pair formation with methylene blue (the limit of detection is 100 ng mL–1), by ion-pair formation with Stains-All (1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl]naphtho[1,2-d]thiazolium bromide) (the limit of detection is 500 ng mL–1), and by reaction of 2-keto-3-deoxyoctonic acid with thiobarbituric acid (the limit of detection is 800 ng mL–1) were proposed. The optimized procedure for 2-keto-3-deoxyoctonic acid was applied for thermal lensing that provided a decrease in the limit of detection to 70 ng mL–1 and was also used for lipopolysaccharide determination in the endotoxin standard from E. coli.
Keywords: Thermal lensing Pyrogens Endotoxins Lipopolysaccharides p-Aminophenol
Detection of odour emissions from a composting facility using a QCM sensor array
by A. S. Yuwono; P. Boeker; P. Schulze Lammers (pp. 1045-1048).
Odour emissions from a composting facility were detected by using a quartz crystal microbalance (QCM) sensor array. The array consists of six sensor elements, which were coated with different materials. A series of tests under field conditions showed that considerable sensor frequency changes were detected during the compost-turning period. Using principal component analysis, it was found that more than 90% of the data variance could still be explained by use of two principal components.
Keywords: Odour Composting facility Sensor array
Analysis of the relationship between the structure and aromatic properties of chemical compounds
by Barbara Dębska; Barbara Guzowska-Świder (pp. 1049-1061).
This paper presents the results of research on the relationship between the structure and odour properties of a selection of chemical compounds. The research concerns five groups of esters, each with a different smell: almond, apricot, apple, pineapple and rose. The supposed relationship between the smell and certain selected attributes of each molecule was examined by various pattern recognition techniques using programs developed in the Department of Computer Chemistry at Rzeszów University of Technology.
Keywords: Smell–structure relationship Prediction of compounds properties
The importance of trace element speciation in biomedical science
by Douglas M. Templeton (pp. 1062-1066).
According to IUPAC terminology, trace element speciation reflects differences in chemical composition at multiple levels from nuclear and electronic structure to macromolecular complexation. In the medical sciences, all levels of composition are important in various circumstances, and each can affect the bioavailability, distribution, physiological function, toxicity, diagnostic utility, and therapeutic potential of an element. Here we discuss, with specific examples, three biological principles in the intimate relation between speciation and biological behavior: i) the kinetics of interconversion of species determines distribution within the organism, ii) speciation governs transport across various biological barriers, and iii) speciation can limit potentially undesirable interactions between physiologically essential elementsWe will also describe differences in the speciation of iron in states of iron overload, to illustrate how speciation analysis can provide insight into cellular processes in human disease.
Keywords: Bioavailability Toxicity Metal–metal interactions Isotopic composition Biokinetics
Speciation of Mg, Mn and Zn in extracts of medicinal plants
by Günther Weber; Paweł Konieczyński (pp. 1067-1073).
Aqueous extracts of birch leaves ( folium Betulae), peppermint leaves ( folium Menthae), sage leaves ( folium Salviae), valerian roots ( radix Valerianae), and dandelion roots ( radix Taraxaci) are analysed for the three essential elements magnesium, manganese and zinc. Ultrafiltration reveals that 60–100% of these metals are present as low molecular weight species (<5000 Da). Further characterisation of the low molecular weight fraction is done by using size exclusion chromatography and different detectors, namely element specific AAS detection, diode array UV–VIS detection and electrochemical detection. The similarities and differences of the plant extracts are well reflected by the respective chromatograms, and typical plant constituents can be identified by their spectral and electrochemical properties (e.g. flavonoids in Betula). Mg and Mn species are selectively detected by AAS in closely neighbouring chromatographic regions for all five samples. However, there are significant differences between the samples investigated. In all cases a good correlation exists between detection of these metals (Mg, Mn) and pulsed amperometric detection (PAD), which is selective for carbohydrates. The respective molecular weight of carbohydrate species is in the range of approximately 300–600 Da. The distribution of zinc species (detectable only in the Betula extract) is totally different from that of Mg and Mn species. For zinc, many more species are detected, and there is no correlation to carbohydrates; instead (poly)phenols are involved in zinc complexation.
Keywords: Speciation Medicinal plants Magnesium Manganese Zinc Electrochemical detection AAS
On-line speciation of bromine and bromide using sequential injection analysis with spectrophotometric detection
by J. F. van Staden; L. V. Mulaudzi; R. I. Stefan (pp. 1074-1082).
An on-line procedure for the simultaneous determination of bromine and total bromine (bromine+bromide oxidised to bromine) is proposed, which lead to the determination of bromide by subtraction. Phenol red was used as chromogenic reagent for bromine and total bromine after bromide was oxidised to bromine by Chloramine T. The linear range found is 1–10 mg L−1 with a detection limit of 0.6 mg L−1 for bromine, and a linear range of 0.8–15 mg L−1 with a detection limit of 0.4 mg L−1 for total bromine. The calculated RSD for bromine is less than 0.8% and for total bromine less than 0.7%. The system is fully computerised and able to run 30 samples per hour with an automated rinsing step that eliminates sample carry-over. The results for both bromine and bromide from the proposed sequential injection analysis (SIA) system compare favourably with standard manual methods and statistical evaluation proves no significant difference between the results of the proposed SIA system and the standard method at the 95% confidence level. The presence of other halides was found not to interfere.
Keywords: Speciation Bromine Bromide On-line Sequential injection analysis Phenol red
Solid-phase reagent for molecular spectroscopic determination of heavy metal speciation in natural water
by Rostyslav P. Linnik; Olga A. Zaporozhets (pp. 1083-1088).
A solid-phase reagent based on 1-(4-adamantyl-2-thiasolylazo)-2-naphthol adsorbed onto silica gel was prepared for Co(II) recovery and preconcentration prior to its sorption-spectroscopic detection. The immobilized reagent was applied to the determination of free cobalt ions in natural water. The solid-phase reagent and chemiluminescent method coupled with membrane filtration, gel-permeation and ion-exchange chromatography were applied to the study of the speciation of iron and cobalt in water from the Dnieper reservoirs and lakes of Kyiv City; their predominant forms were complexes of Fe(III) and Co(II) with dissolved organic matter and fulvic acids play a main role in their complexation.
Keywords: Speciation Iron Cobalt Humic substances Solid-phase reagent 1-(4-Adamantyl-2-thiasolylazo)-2-naphthol
Study of extraction conditions for the quantitative determination of Hg bound to sulfide in soils from Almaden (Spain)
by Rodolfo Fernández-Martínez; María Isabel Rucandio (pp. 1089-1096).
Almaden mine (Spain) is the largest source of cinnabar (HgS) in the world. The purpose of this study is to evaluate, compare and optimize the analytical conditions for the quantitative determination of Hg bound to sulfide in soil samples from mining area of Almaden. A sequential extraction procedure was performed in two stages. The first one was based on a nitric acid leaching. An optimization of certain extraction conditions in this stage was carried out. In order to assess the suitability of the nitric acid leaching, an additional study of possible interfering compounds that might promote the solubility of HgS in nitric acid was developed. The quantitative determination of Hg bound to sulfide was considered in a second stage. A comparative study was carried out among three different procedures: i) extraction with a saturated Na2S solution from the residue remaining in the first stage, ii) microwave assisted dissolution of the remaining Hg in this residue with aqua regia, and iii) quantification by difference between total Hg content and Hg extracted in the first stage.The recoveries of Hg bound to sulfide were found to be comparable for the three proposed procedures. Soil samples coming from Almaden mining area were analysed by this method. The distribution of Hg chemical forms was found to be similar for the two parcels tested, and the recoveries of bound to sulfide Hg ranged from 83% to 96% of total Hg content.
Keywords: Mercury Almaden Speciation HgS Sequential extraction Soil
Tangential-flow ultrafiltration: a versatile methodology for determination of complexation parameters in refractory organic matter from Brazilian water and soil samples
by L. P. C. Romão; G. R. Castro; A. H. Rosa; J. C. Rocha; P. M. Padilha; H. C. Silva (pp. 1097-1100).
In this work the copper(II) complexation parameters of aquatic organic matter, aquatic and soil humic substances from Brazilian were determined using a new versatile approach based on a single-stage tangential-flow ultrafiltration (TF-UF) technique (cut-off 1 kDa) and sensitive atomic spectrometry methods. The results regarding the copper(II) complexation capacity and conditional stability constants obtained for humic materials were compared with those obtained using direct potentiometry with a copper-ion-selective electrode. The analytical procedure based on ultrafiltration is a good alternative to determine the complexation parameters in natural organic material from aquatic and soil systems. This approach presents additional advantages such as better sensibility, applicability for multi-element capability, and its possible to be used under natural conditions when compared with the traditional ion-selective electrode.
Keywords: Complexation parameters Copper Organic matter Humic substances Ultrafiltration Ion-selective electrode
Trace elements determination by energy dispersive X-ray fluorescence (EDXRF) in human placenta and membrane: a comparative study
by P. J. Custódio; M. L. Carvalho; F. Nunes (pp. 1101-1106).
This work is an application of energy dispersive X-ray fluorescence (EDXRF) as an analytical technique for trace elemental determination in human membrane and placenta and elemental concentrations correlations in both tissues. Whole samples were collected during the delivery from healthy mothers and full-term pregnancies. The age of the mother was between 25 and 40 years old, and the weight of the infants ranged from 2.56 to 4.05 kg. Samples were lyophilised and analysed without any chemical treatment. No significant differences in elemental content of placenta and membrane samples were observed except for Ca. Very low levels of Se, As and Pb were observed in all the analysed samples. Zn, considered as one of the key elements in newborn health, was not significantly different in the analysed samples, all of which originated from healthy mothers and healthy babies. The obtained values agree with the literature except for Ca, which is much higher in the studied samples.
Keywords: EDXRF Biological samples Human placenta Elemental analysis Trace elements
Analysis of iodine species in aqueous solutions
by H. Bruchertseifer; R. Cripps; S. Guentay; B. Jaeckel (pp. 1107-1110).
Iodine is a biologically important trace element. Its behaviour in the environment and in human metabolism is determined by the type of iodine species which takes part in chemical reactions. Knowledge of their concentrations is necessary to understand and describe the iodine reaction paths. A separation procedure is proposed for quick determination of common forms of iodine—iodide, iodate ions, molecular iodine and organoiodine (in the form of CH3I). The procedure consists of sequential sorption by passing the sample solution first through a solid-phase extraction cartridge to separate I2 and CH3I from IO3 − and I− then through an anion-exchange resin in a cartridge to retain the latter two species. Each loaded cartridge is eluted to separate the sorbed pair of species. Concentration determination of the resulting four solutions can be performed by standard methods, e.g. by spectrophotometry, tracer counting or with ion-selective electrodes.
Keywords: Iodine species Analysis Separation Solid-phase extraction Ion exchange
Quantitative on-line high-resolution NMR spectroscopy in process engineering applications
by Michael Maiwald; Holger H. Fischer; Young-Kyu Kim; Hans Hasse (pp. 1111-1115).
In many technical processes, complex multicomponent mixtures have to be handled, for example, in reaction or separation equipment. High-resolution NMR spectroscopy is an excellent tool to study these mixtures and gain insight in their behavior in the processes. For on-line studies under process conditions, flow NMR probes can be used in a wide range of temperature and pressure. A major challenge in engineering applications of NMR spectroscopy is the need for quantitative evaluation. Flow rates, recovery times, and other parameters of the on-line NMR experiments have to be optimized for this purpose. Since it is generally prohibitive to use deuterated solvents in engineering applications, suitable techniques for field homogenization and solvent signal suppression are needed. Two examples for the application of on-line NMR spectroscopic experiments in process engineering are presented, studies on chemical equilibria and reaction kinetics of the technically important system formaldehyde–water–methanol and investigations on reactive gas absorption of CO2 in aqueous solutions of monoethanolamine.
Keywords: On-line NMR spectroscopy Reaction monitoring Process monitoring Flow NMR Formaldehyde
Novel infrared optical probes for process monitoring and analysis based on next-generation silver halide fibers
by H. M. Heise; L. Küpper; L. N. Butvina (pp. 1116-1123).
Mid-infrared spectroscopy has proved to be a powerful method for the study of various samples and chemical media as found in different industrial processes. In general, the analysis of such samples takes advantage of the fact that multiple analytes can be quantified simultaneously and rapidly without the need for additional reagents. When compared to near-infrared spectroscopy, for which quartz fiber probes can be successfully applied, the application of previously used mid-infrared fiber materials was restricted due to deficiencies with regard to their optical transmission and mechanical properties. Progress in the quality of infrared transparent silver halide fibers and their extrusion with different cross-sections enabled us to construct several flexible fiber-optic probes of different geometries which are particularly suitable and inert for process monitoring. Transmission and attenuated total reflection measurement techniques have mainly been employed for the analysis of liquid and gaseous media. One larger field, for which results are reported, is chemical reactor monitoring. Other applications are concerned with bio-reactor monitoring, or quasi-continuous measurements for the food industry. Infrared spectroscopic cosmetic assays for determining the chemical composition of skin-care formulations are a further promising field of application, for which an example is given.
Keywords: Fourier-transform infrared spectroscopy Silver halide fiber probes Process monitoring Chemical analysis Attenuated total reflection Transmission spectroscopy
Process analysis of biofilms by photoacoustic spectroscopy
by T. Schmid; C. Helmbrecht; U. Panne; C. Haisch; R. Niessner (pp. 1124-1129).
Biofilms are aggregates of microorganisms and biopolymers which occur at aqueous interfaces. Biofilms play an important role in the degradation of pollutants in natural water systems as well as in wastewater treatment plants. In this communication, the use of photoacoustic spectroscopy (PAS) as a new biofilm monitoring technique is presented. PAS combines features of optical spectroscopy and ultrasonic tomography and allows a depth-resolved analysis of optically and acoustically inhomogeneous media. For the first time, both biofilm and bulk liquid were monitored by photoacoustic sensor heads. In this way, sorption of suspended iron(III) oxide particles on the outer and inner surfaces of the biofilm could be observed on-line and in situ. Colloids can act as carriers of pollutants and influence stability and degradation efficiency of biofilms.
Keywords: Photoacoustic spectroscopy Biofilms Particles Colloids
On-line monitoring of opaque liquids by photoacoustic spectroscopy
by T. Schmid; C. Helmbrecht; C. Haisch; U. Panne; R. Niessner (pp. 1130-1135).
A new photoacoustic sensor system for on-line monitoring of highly concentrated and optical opaque liquid samples is presented. The dyeing of textiles is performed with highly concentrated dye solutions with concentrations ranging from 50 mg L−1 up to 40 g L−1. For process optimization and control of the wastewater, an on-line monitoring of the dye concentration is needed. Optical transmission measurements allow the determination of the dye concentration in a relatively small range. Samples with concentrations in the upper mg L−1 and g L−1 range have to be diluted before the measurement due to their optical opacity. Additionally, light-scattering particles have a strong effect on the transmitted light intensity. By photoacoustic spectroscopy, concentrations in condensed matter can be determined over several orders of magnitude. Furthermore, scattering particles do not generate any photoacoustic signal.
Keywords: Photoacoustic spectroscopy Opaque liquids Textile dyes On-line monitoring
Development and characterization of a mobile photoacoustic sensor for on-line soot emission monitoring in diesel exhaust gas
by H. A. Beck; R. Niessner; C. Haisch (pp. 1136-1143).
Upcoming regulations for vehicle exhaust emission demand substantial reduction of particle emission in diesel exhaust. To achieve these emission levels, the car manufacturing industry is developing new combustion concepts and exhaust after-treatment techniques such as the use of catalysts and particle filters. Many of the state-of-the-art analytical instruments do not meet the required detection limits, in combination with a high temporal resolution necessary for engine optimization. This paper reports a new detection system and the first results of its application to on-line diesel exhaust soot measurements on a engine test bench (MAN diesel engine facility Nürnberg, Germany). The instrument is based on differential photoacoustic (PA) spectroscopy of black carbon aerosol. It contains two identical PA cells, one for the measurement of the aerosol particles and one which analyses the particle-free gas. Thus, a potential cross-sensitivity to gaseous absorbers in the exhaust gas can be excluded. The PA cells were characterized in a laboratory set-up, with water vapor as reference gas and artificial soot generated by a spark discharge generator. The detection limit was found to be 2 µg m-3 BC (for diesel soot) with a sampling rate of 3 Hz. The temporal response of the system was found to be in the order of 1 s. After full characterization of the cells, the system was transferred into a mobile 19"-rack. Characterization of the mobile sensor system under real-world conditions was performed during several measurement campaigns at an engine test bench for heavy-duty diesel engines. Results for the limit of detection, the time resolution, accuracy, repeatability, and robustness of the sensor system are very promising with regards to a routine application of the system in engine development.
Remote, real-time, on-line monitoring of high-temperature samples by noninvasive open-path laser plasma spectrometry
by José M. Vadillo; Pedro L. García; Santiago Palanco; D. Romero; José Mª Baena; J. Javier Laserna (pp. 1144-1147).
A remote detection system based on optical emission spectrometry of laser-induced plasmas has been developed to record spectra in the visible region from samples placed at remote distances from the excitation source. Unlike from fiber-optic-based systems, light collection is performed remotely as well. Laboratory-scale experiments have shown the possibility of performing real-time analysis of samples placed remotely. The application in the noninvasive analysis of hot samples (at 1,200 °C) has been demonstrated as well, allowing the dynamic monitoring of selective elemental migration.
Keywords: Remote analysis Laser plasmas LIPS Stainless steel analysis
Towards a new conservation method for ancient manuscripts by inactivation of iron via complexation and extraction
by B. Wagner; E. Bulska (pp. 1148-1153).
The aim of this work was to study the efficiency of extraction of iron from model paper samples by use of different ligands (deferoxamine mesylate, the potassium–magnesium salt of phytic acid and diethylenetriaminepentaacetic acid) at varied concentrations (0.01, 0.005, and 0.001 mol L−1) and pH (7, 8, 9). Graphite furnace atomic absorption spectrometry (GFAAS) was used to monitor the total amount of iron in solutions of the respective ligands. Two types of model were used to investigate the behaviour of various iron species present in ancient iron-gall ink. Requirements for the optimal procedure, which could possibly be used in the conservation of ancient manuscripts, included high effectiveness of iron extraction from samples which modelled free iron ions (samples "Fe"), while iron deposited in the form of ink (samples "A") should remain without any visible change of the ink's intensity. The best results were achieved with the solution of 0.005 mol L−1 diethylenetriaminepentaacetic acid (pH=9), which allowed extraction of 97±1% of iron from "Fe" model samples and only 64±1% from "A" samples.
Keywords: Iron-gall ink corrosion Paper Iron extraction GFAAS
Analysis of earthy pigments in grounds of Baroque paintings
by Tomáš Grygar; Janka Hradilová; David Hradil; Petr Bezdička; Snejana Bakardjieva (pp. 1154-1160).
Sixteen samples of orange–red and yellow Fe-oxide earthy pigments mainly from bole grounds of Baroque paintings were studied by elemental and phase analysis and voltammetry. Fe, K, and Ti content were found to be suitable for further classification of those earthy pigments. According to the chemical and phase composition the yellow grounds were natural yellow ochres formed by intense chemical weathering in a moderate climate. Very similar phase and elemental composition of part of the orange–red boles indicated their similar geological origin or even their formation by calcination of yellow ochres. Part of the orange–red boles differed significantly from the yellow boles, especially in their increased content of Ti, indicating their relation to end products of intense weathering, e.g. laterites formed in a tropical climate. Analogous materials with a correspondingly large Ti content are not currently commercially available and their geological origin (provenance) is not clear. In several orange–red boles the intentional addition of rather coarse-grained haematite to natural ochre by the painters was assumed on the basis of Fe oxide content and crystallinity.
Keywords: Painting Bole grounds Earthy pigments Haematite
Application of SEM/EDX and metallographic techniques to the diachronic study (6th–18th century) of metallurgical materials found in archaeological excavations on the island of Ibiza (Spain)
by J. V. Gimeno Adelantado; M. A. Ferrer Eres; F. M. Valle Algarra; J. Peris Vicente; F. Bosch Reig (pp. 1161-1168).
This work is the archaeometric study of the different types of materials recovered in the same excavation or archaeological dig (which makes it possible to accurately date the remains found) on the island of Ibiza (Spain). The samples found belong only to the phase of iron forging and span a very wide historical period from the 6th to the 18th century, including the Islamic period. Scanning Electron Microscopy (SEM) is proposed to observe the images obtained of the surfaces of the samples, in order to study the topographical, morphological and microstructural characteristics providing information on the materials contained in the samples. It also permits chemical analysis of the elements in the sample using X-ray Microanalysis (SEM/EDX), which provides both qualitative and semi-quantitative information on the elements in the sample. The archaeometric results suggest that the sole use of the area studied was as a forge workshop over a long period of time. The slag studied show that no reduction or refining activities took place in the area. However, in this forge, pieces of other metals were also produced, especially bronze alloys, polymetallism being a common characteristic throughout history.
Keywords: Archaeological iron Forged object Bronze Slag SEM/EDX Archaeometry
Electrochemical identification of anthraquinone-based dyes in solid microsamples by square wave voltammetry using graphite/polyester composite electrodes.
by A. Doménech-Carbó; M. T. Doménech-Carbó; M. C. Saurí-Peris; J. V. Gimeno-Adelantado; F. Bosch-Reig (pp. 1169-1175).
An electrochemical method for identifying anthraquinone-type dyes in microsamples from works of art, based in the voltammetry of microparticles approach, is reported. Upon attachment onto graphite/polyester composite electrodes, natural pigments aloe, henna, cochineal red, madder lake, kermes, shellac, and alizarin and purpurin taken as reference materials can be identified from their square wave voltammetric profiles in MeCN (0.10 mol L−1 Bu4NPF6) and aqueous (0.25 mol L−1 acetic acid+0.25 mol L−1 sodium acetate) electrolytes.
Keywords: Anthraquinone dyes Square-wave voltammetry Sample-modified electrodes
SEM/EDX and vis spectrophotometry study of the stability of resin-bound mortars used for casting replicas and filling missing parts of historic stone fountains
by José-Luis Roig-Salom; María-Teresa Doménech-Carbó; Juana de la Cruz-Cañizares; Fernando Bolívar-Galiano; María-José Pelufo-Carbonell; Yaiza Peraza-Zurita (pp. 1176-1181).
A study by SEM/EDX and spectrophotometry in the visible region attempting to assess the stability of new resin-bound mortars used for casting replicas of marble historic fountains is presented in this paper. Different accelerating tests such as thermal ageing, UV light ageing, ageing in an SO2 pollutant chamber, freezing cycles ageing, salt crystallisation ageing, natural ageing and biological attack have been applied to a series of test specimens prepared with polyester-, epoxy- and gel-coat-bound mortars. Examination of morphology, measurement of chemical composition and chromatic coordinates before and after ageing treatments establish the higher stability and resistance properties of these resin-bound mortars by comparison to those from the natural marbles.
Keywords: Resin-bound mortars Synthetic polymer Fountain Marble SEM/EDX Spectrophotometry Biological attack
Influence of the nature of the pasting liquid on the accumulation of nitroanilines at carbon paste electrode during determination by absorptive stripping voltammetry
by N. Kuz'mina; F. Kudasheva; V. Maistrenko; S. Sapel'nikova (pp. 1182-1185).
The accumulation of ortho-, para-nitroanilines, 2,4-dimetyl-6-nitroaniline, and meta-nitrobenzoic acid at carbon paste electrode (CPE) has been studied. For the preparation of CPE different pasting liquids have been used: esters, aromatic hydrocarbons, saturated hydrocarbons, and polymethylsiloxane. Distribution ratios of o- and p-nitroanilines between the pasting liquid and water have been determined. Correlation between peak current constants and distribution ratios has been found. It has been demonstrated that during the determination of analyte on the CPE with aromatic hydrocarbons, the main influence on nitro-compound accumulation is executed by the extraction into the pasting liquids, and on the CPE with saturated hydrocarbons – by the process of depolarizer sorption onto the graphite. The selective determination of nitroanilines in the presence of hindering compounds with adsorptive stripping voltammetry has been carried out.
Keywords: Carbon paste electrode Nitroanilines Absorptive stripping voltammetry Extraction
A novel 1,10-phenanthroline-sensitive membrane sensor for potentiometric determination of Hg(II) and Cu(II)cations
by Sayed A. M. Marzouk; Wadie T. Al-Ariqui; Saad S. M. Hassan (pp. 1186-1192).
Preparation, characterization, and applications of a 1,10-phenanthrolinium cation (phenH+)-sensitive potentiometric sensor are described. The sensor incorporates a liquid polymeric membrane consisting of phenH-tetraphenylborate, nitrophenyloctyl ether, and poly(vinyl chloride) as ion exchanger, plasticizer, and polymeric support, respectively. The sensor exhibits a fast and Nernstian response to phenH+ over the concentration range of 6×10−6–2×10−4 M with a monovalent cationic slope of 58.0±0.5 mV/log[phenH+] in acetate buffer of pH 4.2. The sensor is successfully applied to the monitoring of the potentiometric titration of Hg(II) and Cu(II) ions with phen solution in the presence of citrate and acetate buffers of pH 4.2, respectively. Sharp inflection breaks (90–180 mV) at 1:1 (metal:phen reaction) are obtained in the presence of chloride and thiocyanate background. This stoichiometry is explained by the formation of insoluble [HgCl2(phen)], [Hg(SCN)2(phen)], and [Cu(SCN)2(phen)] complexes. Optimization of each titration and the effect of foreign ions are evaluated. The method offers the advantages of adequate sensitivity, accuracy, and selectivity for the determination of mercury and copper in pharmaceutical, rock, and tea samples. The results are in good agreement with those obtained using the standard atomic absorption spectrometric and United States Pharmacopeial methods.
Keywords: Polymeric membrane sensors Potentiometric titration 1,10-Phenanthroline Determination of Hg(II) and Cu(II) Copper in tea Mercury in pharmaceuticals
Monomer and polymer quinoxaline derivatives for cationic recognition
by H. Březnová; R. Volf; V. Král; J. L. Sessler; A. C. Try; T. V. Shishkanova (pp. 1193-1198).
Monomeric and polymeric 5-nitroquinoxaline derivatives disubstituted in the 2 and 3 positions with 2-pyrrolyl (A), 2-furyl (B) and 2-thienyl (C) groups were prepared and characterized. The substituted 5-nitroquinoxalines were used as active components in poly(vinyl chloride)-membrane and electropolymerized electrodes that were then tested as possible sensors for various cationic species. In contrast to the difurylnitroquinoxaline-based systems, the monomeric and polymeric dipyrrolyl- and dithienylquinoxaline electrodes displayed a good selectivity for Ag+ ions, providing a near-Nernstian response in the 10−5 to 10−2 mol L−1 concentration range. The similar potentiometric behavior displayed by the monomeric and polymeric forms of systems A and C supports the contention that the main binding modes displayed by the monomeric forms are retained in the corresponding polymeric structures.
Keywords: Nitroquinoxaline Ion-selective electrode Cationic selectivity
Application of polyelectrolyte complexes as novel pseudo-stationary phases in MEKC
by A. V. Pirogov; A. V. Shpak; O. A. Shpigun (pp. 1199-1203).
Polyacrylic acid (PAA) and polymethacrylic acid (PMAA) with carboxyl groups partially blocked by dodecyltrimethylammonium bromide (DTAB) and tetrabutylammonium bromide (TBAB) were tested as new pseudo-stationary phases in micellar electrokinetic chromatography (MEKC). The separation of was examined using PAA and PMAA. Excellent resolution of the substituted phenols and derivatized amino acids was demonstrated using additives of PAA-DTAB polyelectrolyte complex in the running phosphate buffer. It was found that the capacity factors were proportional to the concentration of the complex PAA/DTAB. Critical micelle concentration was effectively zero. It was found that the migration times and efficiency of separation of phenols and derivatives of amino acids depended on the type of polymers and alkyltrimethylammonium salts used.
Keywords: Capillary electrophoresis Pseudo-stationary phases MEKC Polyelectrolyte complexes Polyacrylic acid Polymethacrylic acid
Optical photothermal detection in HPLC
by M. A. Proskurnin; A. Yu. Luk'yanov; S. N. Bendrysheva; A. A. Bendryshev; A. V. Pirogov; O. A. Shpigun (pp. 1204-1211).
A mode-mismatched parallel dual-beam thermal lens spectrometer with a far-field single-channel detector system was used as a detector in HPLC. An expert estimation of the measurement results was applied to optimize the optical-scheme configuration of the spectrometer to achieve the longest linear calibration range and highest repeatability under chromatographic flow conditions. Chelates with 4-(2-pyridylazo)resorcinol were separated and determined with the limits of detection of n × 10−8–n × 10−7 mol L−1; the relative standard deviation of measurements was 46%. Xylenol Orange, 4-(2-thiazolylazo)resorcinol, and dithizone were studied as post-column reagents in thermal lens detection in ion chromatography. The limits of detection were n × 10−8–n × 10−7 mol L−1; the linear calibration ranges were about three orders; the relative standard deviation of measurements was 3–7%. A combined photothermal–refractometric detector for HPLC based on a polarization interferometer is proposed. Metal complexes as 4-(pyridylazo)resorcinol chelates (limits of detection of n × 10−8–n × 10−7 mol L−1) and sugars (limits of detection of 10–20 ng L−1) were investigated as model substances. Obtained results were compared with results for traditional detectors, which show that photothermal detection has higher sensitivity than photometric and other absorption detectors.
Keywords: Thermal lensing Photothermal interferometry, Optical-scheme design optimization HPLC Ion chromatography
Optimization of gas chromatography using short glass capillary column with mass spectrometry for identification and evaluation of commercial heavy alkylbenzene structures
by S. M. Ghoreishi; M. Beiggy; M. Mazloum Ardekani (pp. 1212-1220).
Heavy alkylbenzene (HAB) is one of the by-products when producing linear alkylbenzene (LAB). Identification of the fine structures of HAB is difficult because of its complex structure and high boiling point. The gas chromatography/mass spectrometry (GC/MS) technique with a short glass capillary column is the best method applicable to analysis of high-boiling and thermally labile compounds. The column efficiency is evaluated on the basis of Van Deemter curves.The experimental results show that the reduction in the optimum column efficiency for a short glass capillary column occurs along with a reduction in effective theoretical plates. A second important result is that the shift in the value of the flow velocity is related to the optimum point in height equivalent theoretical plate (HETP). The flow velocity is higher than that of conventional gas chromatography(GC).The optimized conditions were used to analyse HAB produced through the hydrogen fluoride (HF) alkylation process. The results show acceptable relative separation of a product in an extended boiling point range. The optimized conditions were also used to analyse three other special samples supplied by BASF company's AlCl3 alkylation process and to approve the previous structures. The results also show that HAB from Iran Chemical Industries Investment Company (ICIIC) produced through LAB complex consists of an additional part and has more linearity than the other three samples of HAB obtained from BASF.
Keywords: GC/MS Heavy alkylbenzene LAB Optimization
Heterocyclic acetals in Madeira wines
by J. S. Câmara; J. C. Marques; A. Alves; A. C. Silva Ferreira (pp. 1221-1224).
The maturation of Madeira wines usually involves exposure to relatively high temperatures which affect the aroma and flavour composition leading to the formation of the typical and characteristic bouquet of these wines. The formation of heterocyclic acetals (1,3-dioxanes and 1,3-dioxolanes) was investigated in order to determine levels and for possible use as indicators of wine age. The results show a linear correlation of the investigated acetals with wine age but suggest that the acetalization reaction is not particularly affected by the drastic oxidative conditions observed during maturation.
Keywords: Acetals 1,3-Dioxanes 1,3-Dioxolanes Wine-ageing Madeira wine GC–MS
Microwave extraction of organochlorine pesticides from soils
by E. Concha-Graña; M. Barriada-Pereira; M. I. Turnes-Carou; S. Muniategui-Lorenzo; P. López-Mahía; D. Prada Rodríguez (pp. 1225-1228).
The purpose of this work was to develop a rapid, reliable and sensitive method for the extraction of organochlorine pesticides from soils using microwave energy with closed vessel technology. Three oven programs were assayed with two different solvent mixtures in order to achieve adequate experimental conditions for the complete extraction of organochlorine pesticides from the matrix. The method was validated using a certified reference soil material (CRM804-050).
Keywords: Organochlorine pesticides Soil analysis Microwave-assisted extraction Pesticides Environmental analysis GC-ECD
On-line ion-exchange preconcentration and determination of traces of platinum by electrothermal atomic absorption spectrometry
by M. M. González García; F. Sánchez Rojas; C. Bosch Ojeda; A. García de Torres; J. M. Cano Pavón (pp. 1229-1233).
A method to determine trace amounts of platinum in different samples based on electrothermal atomic absorption spectrometry is described. The preconcentration step is performed on a chelating resin microcolumn [1,5-bis(2-pyridyl)-3-sulfophenyl methylene thiocarbonohydrazide (PSTH) immobilized on an anion-exchange resin (Dowex 1×8–200)] placed in the autosampler arm. The combination of a peristaltic pump for sample loading and the atomic absorption spectrometer pumps for elution through a selection valve simplifies the hardware. The peristaltic pump and the selection valve are easily controlled electronically with two switches placed in the autosampler, which are activated when the autosampler arm is down. Thus, the process is fully automated without any modification of the software of the atomic absorption spectrometer. Under the optimum conditions with a 60-s preconcentration time, a sample flow rate of 2.4 mL min−1, and an injection volume of eluent of 40 µL, a linear calibration graph was obtained in the range 0–100 ng mL−1. The enrichment factor was 14. The detection limit under these conditions is 1 ng mL−1, and the relative standard deviation (RSD) is 1.6% for 10 ng mL−1 of Pt. The method has been applied to the determination of platinum in catalyst, vegetation, soil, and natural water samples. The results showed good agreement with the certified value and the recoveries of Pt added to samples were 98–105%.
Keywords: Platinum Electrothermal atomic absorption spectrometry Preconcentration Microcolumn Flow injection Vegetation, soil, waters, and catalyst samples
Sampling strategies exploiting multi-pumping flow systems
by João A. V. Prior; João L. M. Santos; José L. F. C. Lima (pp. 1234-1239).
In this work new strategies were exploited to implement multi-pumping flow systems relying on the utilisation of multiple devices that act simultaneously as sample-insertion, reagent-introduction, and solution-propelling units. The solenoid micro-pumps that were initially used as the only active elements of multi-pumping systems, and which were able to produce pulses of 3 to 25 μL, were replaced by syringe pumps with the aim of producing pulses between 1 and 4 μL. The performance of the developed flow system was assessed by using distinct sample-insertion strategies like single sample volume, merging zones, and binary sampling in the spectrophotometric determination of isoniazid in pharmaceutical formulations upon reaction with 1,2-naphthoquinone-4-sulfonate, in alkaline medium. The results obtained showed that enhanced sample/reagent mixing could be obtained with binary sampling and by using a 1 μL per step pump, even in limited dispersion conditions. Moreover, syringe pumps produce very reproducible flowing streams and are easily manipulated and controlled by a computer program, which is greatly simplified since they are the only active manifold component. Linear calibration plots up to 18.0 μg mL−1, with a relative standard deviation of less than 1.48% (n=10) and a throughput of about 20 samples per hour, were obtained.
Keywords: Multi-pumping flow systems Binary sampling Isoniazid 1,2-Naphthoquinone-4-sulfonate Pharmaceuticals
Surface plasmon resonance and Raman scattering effects studied for layers deposited on Spreeta sensors
by Pavel Matějka; Pavel Hrubý; Karel Volka (pp. 1240-1245).
The possibility to detect and prospectively to characterize deposited organic layers directly on Spreeta sensors by Fourier transform Raman spectroscopy was studied. A special holder of sensors that enabled measurement of FT Raman spectra was developed. The effects of various angles of incidence of the laser beam on the sensor surface were studied with respect to the intensity of Raman spectra and to the risks of artifacts. No effect of measurement of FT Raman spectra on SPR functionality of sensors was proven. The key role of the surface morphology of the sensing gold layer on repeatability of SPR curves and the possibility to check the surface by optical microscopy was demonstrated.
Keywords: Surface plasmon resonance FT Raman spectroscopy Deposited layers Optical sensor Sensing surface
Vibrational analysis of 2-[4-( N -dodecanoylamino)phenyl]-5-(4-nitrophenyl)-1,3,4-oxadiazole
by B. Jordanov; D. Tsankov; K. Hinrichs; R. Dietel; E. H. Korte (pp. 1246-1249).
The infrared absorption spectra of 2-[4-( N -dodecanoylamino)phenyl]-5-(4-nitrophenyl)-1,3,4-oxadiazole (also denoted AF51) in solution and in the solid state as well as the solid-state Raman spectrum of the powdered compound are compared with the infrared linear dichroic (LD) spectra recorded at two orthogonal polarizations. The IR-LD spectra were measured in an anisotropic solvent—the nematic liquid crystal ZLI-1695 (Merck). The solvent spectrum taken under precisely the same experimental conditions and polarized radiation azimuths was subtracted from the polarized sample spectra in order to achieve pure oriented spectra of the compound studied. These spectra were further processed using a stepwise reduction procedure that allows for assignment of vibrational modes having mutually orthogonal dipole moments.
Keywords: IR polarized spectra Nematic solutions 1,3,4-Oxadiazoles
Fourth-derivative spectrophotometric determination of fungicide ferbam (iron(III) dimethyldithiocarbamate) in a commercial sample and wheat grains using 2,2′-bipyridyl
by Ashok Kumar Malik; Sonam Bansal; Jatinder Singh Aulakh (pp. 1250-1253).
A procedure has been developed for the direct fourth-derivative spectrophotometric determination of iron(III) dimethyldithiocarbamate by converting it into an iron(II) 2,2′-bipyridyl complex, which is then dissolved in Triton X-100. Beer's law is obeyed over the concentration range 0.5–20 µg mL−1 in the final solution. Various parameters such as the effect of pH and interference of large number of ions on the determination of ferbam have been studied in detail. The method is sensitive, highly selective and can be used for the determination of ferbam in a commercial sample and in mixtures with various dithiocarbamates (ziram, zineb, maneb, etc.) and from wheat grains.
Keywords: Ferbam determination Derivative spectrophotometry Commercial sample 2,2′-Bipyridyl Residue analysis
Comparison of three spectrophotometric methods for the determination of γ-oryzanol in rice bran oil
by Remo Bucci; Andrea D. Magrì; Antonio L. Magrì; Federico Marini (pp. 1254-1259).
A comparison of the results obtained by applying three spectrophotometric methods (at fixed wavelength, second-derivative and multicomponent analysis) to the determination of γ-oryzanol in rice bran oil is reported.At fixed wavelength the results are more accurate when using isopropyl alcohol, rather than n-heptane, to dilute the oil samples, because the absorption bands of γ-oryzanol are red-shifted and the absorbance, measured at λmax=327 nm, is less affected by the interference of the oil "matrix" (λmax=314 nm in n-heptane).However, to obtain accurate results also in oils with a low content of γ-oryzanol, it is necessary to perform the analysis using second-derivative (2D330.365) or multicomponent (λ=310–360 nm) methods. The first one fully removes the interference of oil matrix whilst the second, which needs a specific computational program to process the spectrophotometric data, furnishes evidence the presence of some unexpected interference in the analysis and/or standards which are not representative of the analysed samples, from the square root of the sum of the squared differences at each point between the linear combination of the standards and the unknown spectra (RMS error).Finally, some aspects of the chemical, spectroscopic (UV, IR) and thermoanalytical (TG, DSC) behaviour of γ-oryzanol and the values of the parameters which enable "computation" of its UV spectra are reported.
Keywords: γ-Oryzanol Spectrophotometry Rice bran oil
Use of a multichannel photometer (Multiskan MS) for determination of humic materials in soil after their dichromate oxidation
by Alvyra Slepetiene; Bronislava Butkute (pp. 1260-1264).
Methodology for the determination of humus and humic materials content in soil after dichromate oxidation using a multichannel automatic photometer (Multiskan MS) has been developed. The study presented here demonstrates the benefits of using this methodology for the rapid, reliable and accurate determination of humus and humic materials content in various soils. The method is characterised by good data repeatability and low labour and reagent inputs. Photometric estimation is assessed in various respects, and determination procedures are presented. We have compared the data obtained by the titrimetric method and the photometric method with the photometer Multiskan MS. The methods are well correlated. The regression equations and determination coefficients relating to the data obtained by different methods have been calculated. The best statistics of a comparison between the titrimetric (y) and photometric (x) methods of humus determination were obtained with a series of standards prepared from the soil samples of known humus content: R 2=0.99; y=1.05x−0.37; BIAS=0.24% of humus; SED=0.27% of humus.
Keywords: Humic materials Organic carbon Soil Titrimetric and photometric determination Multiskan MS
Application of LA–ICP–MS in polar ice core studies
by H. Reinhardt; M. Kriews; H. Miller; C. Lüdke; E. Hoffmann; J. Skole (pp. 1265-1275).
The direct determination of element signatures in polar ice core samples from Greenland by laser ablation with subsequent inductively coupled plasma mass spectrometry analysis has been investigated. A cryogenic sample chamber enables the element determination in ice directly from the solid (frozen) state. A procedure was developed to analyse up to 38 elements (traces: Mg, Al, Fe, Zn, Cd, Pb and rare earth elements; minor constituents: Na) in ice samples from Greenland with a previously unachievable spatial resolution of 4 mm along the core axis. This resolution is helpful to detect seasonal variations of element concentration in thin annual layers of deep ice. We report operating conditions and analytical performance of the experimental set up, the improvement of signal stability by 17OH internal standardisation and application of a desolvation unit. Calibration of the system was performed with frozen multielement standard solutions along a special preparation procedure. Detection limits for the tracers Na, Mg (sea salt), Al (mineral dust) and Zn (anthropogenic source) are 0.1–1 µg kg−1. Best detection limits in the range of 0.001–0.01 µg kg−1 were reached for Co, Pb and all rare earth elements. To validate the method, frozen standard reference materials were measured. The recovery is about ±10%. Greenland ice core samples from different ages were analysed with the new technique. The results obtained by laser ablation were compared with values from solution analysis, available published data and the particle content. Most elements have shown good correlation with the particle content in the Greenland samples; however, differences could be seen between the values obtained by laser ablation and solution bulk analysis after a tri-acid digestion. The influence of particles is discussed. The high spatially resolved 2D mapping of element concentrations shows strong inhomogeneities along the core axis most probably due to seasonal variations of element deposition.
Keywords: LA–ICP–MS Ice core 2D mapping Cryogenic chamber Element signatures Greenland Polar research
X-ray photoelectron spectroscopy for detection of the different Si–O bonding states of silicon
by Dieter Pleul; Ralf Frenzel; Michael Eschner; Frank Simon (pp. 1276-1281).
X-ray photoelectron spectroscopy (XPS) was used to detect the bonding between a silica particle surface and attached silanes. In addition to the commonly recorded Si 2p spectrum, the Si 1 s level is also accessible when monochromatic Ag Lα X-rays are applied. Furthermore, the spectrum of the Si 1 s level shows a fine structure. After spectrum deconvolution, we assigned the fitted spectral peaks to Si–C bonds of the silanes and to the Si–O bonds of the silica network. The recorded Si 1 s spectra were deconvoluted into peaks originating from Si–C bonds and the Si–O–Si silica network. To check the results of spectrum deconvolution, several differently functionalized silanes containing stoichiometric amounts of heteroatoms were applied for silica surface modification. We conclude that spectra deconvolution of the Si 1 s signal is an appropriate means for quantification of surface attached silane molecules.
Keywords: X-ray photoelectron spectroscopy (XPS) Silane coupling agents Silanization Silica
Study of the morphology of a laser-produced aerosol plume by cavity ringdown laser absorption spectroscopy
by Valery Bulatov; Aktam Khalmanov; Israel Schechter (pp. 1282-1286).
Cavity ring-down laser absorption spectroscopy (CRLAS) was applied for the first time to detection and characterization of laser breakdown generated aerosols. The method provided time-resolved morphological information on the aerosol plume, which is of importance in laser ablation (LA) and deposition, in laser-induced breakdown spectroscopy (LIBS) analysis, and in laser ablation inductively coupled plasma (LA–ICP) methods. This method provides sensitive detection of a variety of aerosols produced under ambient conditions. The morphological investigation revealed that the aerosol density has a reproducible pattern as a function of distance from the surface, although its details depend on time, on geometrical parameters and on the surface characteristics.
Keywords: Cavity ring-down Laser ablation Aerosols Laser-induced breakdown spectroscopy (LIBS)