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Analytical and Bioanalytical Chemistry (v.361, #3)

Analytical Chemistry in Russia by Y. A. Zolotov (pp. 223-226).
Analytical Chemistry in the former Soviet Union and Russia is considered. Areas of the present analytical science in the country are noted and significant achievements are mentioned. Important centers of the researches are listed and education in Analytical Chemistry is examined.

The importance of the Avogadro constant for amount-of-substance measurements by P. De Bièvre; S. Valkiers; P. D. P. Taylor (pp. 227-234).
One of the routes to re-determine the Avogadro constant requires ultra-high accuracy isotopic measurements of amount ratios of Si isotopes to 10–5 reproducibilities on the ratio measurements and calibrating the results by synthetic isotope mixtures prepared to 2 · 10–5 relative combined uncertainty. The route to these results is described, followed by a description of the improvement of our knowledge of the Avogadro constant N A through these measurements. The same route has recently been opened for other gases and has opened the way to the establishment of “Primary Standards of Measurements” for gas isotopic measurements. It is described how these highly accurate measurements of ratios of amount of substance have considerably contributed to clearer thinking about concepts for measurements of amount of substance. The acquired expertise in measurement instrumentation and measurement procedures can now be extended to a more general use in measurements of isotope amount ratio (i.e. in other elements). It can also be combined with isotope dilution. This latter combination opens up a new route towards a realization of traceability of an amount-of-substance measurement to the SI and to the (measurement procedure and instrumentation leading to) Avogadro constant.

The methodology of knowledge acquisition from the collection of IR and UV spectra by B. D˛ebska; B. Guzowska-Świder (pp. 235-238).
An expert system for identification of parts of chemical molecules from IR and UV spectra is described. To develop the system, the intelligent knowledge engineering program environment SCANKEE1 (elaborated at the Department of Computer Chemistry) was applied. The expert systems for identification of a chemical compound described in the literature use hand-crafted knowledge bases. To eliminate the time-consuming writing of the rules, a module for the automatic creation of rule knowledge bases was developed. The knowledge derives from the collection of molecular spectra of organic compounds and their structural formulae. The algorithm for the automatic generation of the production rules (in the rule knowledge base) is realized in two steps: (i) the creation of the correlation tables and (ii) the generation of the production rules base.

Molecular recognition: Supramolecular, polymeric and biomimetic coatings for chemical sensors and chromatographic columns by T. Wessa; Wolfgang Göpel (pp. 239-245).
Complete control of the selective and reversible interaction of molecules from the gas or liquid phase at complementary recognition sites is of increasing interest for both basic science and practical applications. This recognition may occur at the surface or in the bulk of optimized chemically sensitive coatings. It is either monitored discontinuously by chromatography or continuously by a suitable sensor. The latter contains the optimized coating and converts the chemical information about concentrations of certain molecules by means of a certain transducer into an electronic signal. Generally speaking, these transducers form the essential part of ‘chemical sensors’; they monitor the molecular interactions at the chemically sensitive layer by changes in resistivity, impedance, mass, capacitance, work function, heat, electrochemical potential, optical thickness, or optical absorption in a certain spectral range. Three selected case studies of such molecular recognition devices which utilize supramolecular, polymeric, and biomimetic coatings are presented. Examples are given for both gas and liquid sensing devices. For simplification, because of its general applicability and its easy absolute calibration, particular emphasis is put on signal transduction via quartz crystal oscillators. The measurement principle is based on frequency changes which are directly correlated with mass changes and thus provide a particularly suitable signal transduction. The examples presented here concern systematic variations in the design of supramolecular cages, of selective interaction sites in polymeric matrices, and of covalently attached biomimetic recognition sites to monitor antibodies or enzyme interactions.

Capillary electrophoresis and inductively coupled plasma spectrometry: Status report by Ramon M. Barnes (pp. 246-251).
This report focuses on the status, requirements, and potentials of CE-ICP-MS. The ultimate goal of a viable CE-ICP-MS system is to obtain quantitative elemental speciation information and isotopic ratio data for practical biological and environmental metal containing compounds. To make use of the CE separation features, the CE analyte must be introduced efficiently into the ICP. For practical samples, pre- and post-separation enrichment techniques probably are required. The features of electrospray ion sources that can be incorporated in CE-ICP-MS and the potential for microfabricated CE are discussed.

Electrochemical properties of photocurable membranes for all-solid-state chemical sensors by S. Levitchev; A. Smirnova; A. Bratov; Y. Vlasov (pp. 252-254).
The development of ion-selective electrodes with inner solid contact is described using photocurable acrylated polyurethane matrices and electron-ion exchanger (EI), which provides a reversible transition from electrical conductivity in the metal to ionic conductivity in the membrane phase. The application of a photocurable polymer matrix gives the possibility to use modern photolithographic techniques for the formation of all-solid-state chemical sensors. The influence of the polymer matrix and of the preparation of the membrane on the electro-chemical properties of calcium-selective membrane sensors is shown. For carbonate-selective membranes the possibility of improvement of electrochemical characteristics by incorporation of the anionic additive tetrakis (4-chlorophenyl) borate was studied.

Non-selective chemical sensors in analytical chemistry: from “electronic nose” to “electronic tongue” by Y. Vlasov; Andrey Legin (pp. 255-260).
Development, recent historical background and analytical applications of promising sensor instruments based on sensor arrays with data processing by pattern recognition methods have been described. Attention is paid to the “electronic tongue” based on an array of original non-specific (non-selective) potentiometric chemical sensors. Application results for integral qualitative analysis of beverages and for quantitative analysis of biological liquids and solutions, containing heavy metals are reported. Discriminating abilities and precision obtained allow to consider “electronic tongue” as a perspective analytical tool.

Direct sampling time-of-flight mass spectrometers for technological analysis by Alexander A. Sysoev; Alexey A. Sysoev; S. S. Poteshin; V. I. Pyatakhin; I. V. Shchekina; A. S. Trofimov (pp. 261-266).
The practicability of direct sampling time-of-flight mass spectrometers for routine technological analysis is considered. The discussed set incorporates two TOF instruments together covering analysis of solid, liquid, and gas samples without the need for time consuming sample preparation. Both an electron ionization reflectron TOF mass analyzer designed for the analysis of gas and liquid samples and a laser ionization axial electrostatic TOF mass analyzer designed for analysis of solid and powder samples use a single system for data acquisition, collection and processing. These instruments achieve ng/g range sensitivity and mass resolution exceeding 1000. Because of its compact design the system also can be realized as a mobile laboratory for on-site analysis. Prospects for applying the instruments to different technological applications are discussed.

Speciation of metal complexes with biomolecules by reversed-phase HPLC with ion-spray and inductively coupled plasma mass spectrometric detection by Hubert Chassaigne; R. Lobinski (pp. 267-273).
Complementarity of ion-spray MS and ICP-MS as detection techniques in reversed-phase HPLC for the characterization of metals complexed by biomacromolecules is discussed by the example of the speciation of metallothionein-bound cadmium. The commercially purified rabbit liver MT-2 isoform is eluted from a microbore C8 column with a gradient of up to 50% methanol in acetate buffer (pH 6.0) to give one major and three minor peaks detected at 254 nm. The preparation is further characterized by using an ICP mass spectrometer interfaced with HPLC via a direct injection nebulizer which allows for the specific detection of cadmium down to the 10 ng mL–1 level. On-line detection by mass spectrometry with an ion-spray (pneumatically-assisted electrospray) ion source further allows the determination of the molecular masses of the eluted compounds.

Modeling of internal pH-gradients in chromatofocusing by A. V. Garmash; A. B. Tessman; P. N. Nesterenko; A. V. Ivanov (pp. 274-275).
A new model of the internal pH-gradient formation, based on the description of both homogeneous and heterogeneous equilibria through explicit forms of appropriate equilibria constants is proposed. The corresponding program “CF” for computation of the profile of an internal pH-gradient generated in systems containing a weak anion-exchanger and mixture of acids as an eluent was developed based on this model. The crucial effect of ionic strength on the profile of pH-gradient was found for the first time.

Determination of the true form of overlapping peaks, deformed by the base line in the case of stripping voltammetry by A. G. Stromberg; S. V. Romanenko (pp. 276-279).
A way to determine the form of an analytical signal without accounting of the base line is described. It is based on subtraction of two peaks. The validity of correction of the base line inclination with the help of a linear function is indicated. The ability to determine the true form of the analytical signal in case of overlapping signals is proved. The approach was applied to define the degree of non-additivity of the analytical signal and the character of change of the peak shape as a function of concentration.

Calibration model of simultaneous multielement atomic-emission analysis using analytical line groups of each determined element by Irina E. Vasilyeva; Elena V. Shabanova (pp. 280-282).
A calibration model of multielement methods for simultaneous determination of micro- and macro-concentrations of elements by computing the arc atomic-emission spectra has been developed. A calibration procedure for the analytical line group of the elements to be determined is offered. It allows the lower and upper limits of the concentration range for each line of the determined element to be calculated by means of the least-square method (LSM) and the Weibull distribution law is used to extend the concentration region. The calibration model was successfully tested for different arc optical emission spectroscopy (OES) methods.

Use of four-factorial design in ion-selective potentiometry for analysis of multi-ionic solutions by A. Akhmetshin; V. Baranovsky; A. Akhmetshina (pp. 282-284).
Even with small selectivity of electrodes the application of multi-factorial design produces good results for complex ion mixtures. Carrying out serial analyses with this method, the time for the preparation of specimens is shortened and the accuracy of the determination is increased. The electrode selectivity is characterized using regression equations and an interference level diagram. A graphical representation of data is suggested taking into account the dependence of response on the number of interfering cations.

True detection limit of rare earth elements in atomic emission analysis with an arc two-jet plasmatron by Elena V. Smirnova; I. E. Vasilyeva (pp. 285-286).
The “true detection limit” CL,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of CL,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show that there is a significant increase of CL,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra.

X-Ray analysis of aqueous concentrates using organic glassy specimens by L. P. Eksperiandova; A. B. Blank; I. I. Fokina (pp. 287-288).
A simple and accessible method for the production of glassy specimens from aqueous concentrates based on saccharose is proposed. During the process of such a specimen preparation an additional concentration of impurities takes place. These saccharose specimens were used for the X-ray fluorescence determination of Se in waste water with crystallization preconcentration.

Silicas modified by polyelectrolyte complexes for the ion chromatography of anionic complexes of transition metals by A. V. Pirogov; N. V. Svintsova; O. V. Kuzina; O. V. Krokhin; M. M. Platonov; O. A. Shpigun (pp. 288-293).
An approach, which is based on the fact that an anion-exchange layer may be bound at the surface of a cation-exchanger by electrostatic interaction of reversibly-charged functional groups, was used for producing polyelectrolyte anion-exchangers. Water-soluble polymers containing positively charged nitrogen atoms were used instead of anion-exchanging latex. A sulfonated co-polymer of styrene and divinylbenzene was replaced with a sorbent for reversed-phase chromatography (silica coated with dodecylbenzenesulfonic acid). The ion-chromatographic behavior of transition metal complexes with ethylenediaminetetraacetic acid (EDTA) and cyclohexanediaminetetraacetic acid (CDTA) separated on sorbent Silasorb-C18, modified by polyvinylpyridinium bromide (PEVP), polydimetyldiallylammonium chloride (PDMDAA), and polyhexamethyleneguanidine chloride (PGMG) was investigated. The limits of detection were 0.1–1 mg/L and 0.01–0.05 mg/L for single and dual-columns, respectively. A comparison of synthesised Silasorb C18-DBSA-PEVP anion-exchanger with several commercial packed materials (Hiks-1, Anieks, TSK gel IC-Anion-PW, TSK gel IC-Anion-SW, BT XI An, Nucleosil 10 SB) was carried out. It was shown that BT I An and BT II An anion-exchangers cannot be used in determining transition metal complexes with EDTA due to high non-ion-exchange sorption of hydrophobic complex anions on the polymer matrix. Silasorb C18-DBSA-PEVP showed the highest selectivity in separating anion complexes of transition metals with EDTA.

Optimization of instrumental neutron activation analysis for studying the chemical composition of silicate rocks by N. Shubina; G. Kolesov (pp. 294-296).
Software for optimization of instrumental neutron activation analysis of geological samples, preferentially silicate rocks, and a technique for evaluation and minimization of interference of gamma-ray lines are given. The maximum relevant signal-to-noise ratio was taken as a criterion for optimization by taking into account information available from a large number of lines in the gamma spectra studied.

Membranes for chemical sensors selective to doubly charged anions by A. Smirnova (pp. 296-300).
The main results concerning selective properties for carbonate, sulfate and phosphate polyvinyl chloride (PVC) membranes based on neutral carriers and anion-exchangers are discussed. It is shown that for the investigated systems selectivity depends on the concentration ratio between anion-exchanger and neutral carrier. The shape of the curves (selectivity vs. neutral carrier concentration) corresponds to a mathematical model described earlier and determines the stoichiometry of the complexes of the anions with neutral carrier. The incorporation of anionic sites inside the anion-selective membrane, e.g., carbonate-selective, leads to an increase of carbonate selectivity in presence of lipophilic anions of the internal solution.

New test tools: Benzidine on cellulose and silica gel by V. M. Ostrovskaya; Y. A. Zolotov; E. I. Morosanova; D. Y. Marchenko (pp. 300-303).
Chromogenic reagents based on covalent and non-covalent immobilization of benzidine on cellulose and silica gels have been developed and investigated. New test tools and test methods have been elaborated for the determination of chlorine in the concentration range of 0.05–120 mg/L.

New test tools for determination of trace metals using polydentate cellulose by V. M. Ostrovskaya (pp. 303-305).
New test tools have been developed for the rapid determination of trace metals: Ag, Cd, Co, Cu(II), Fe(II,III), Hg(II), Pd and Zn, using polydentate irregular α-celluloses, containing in the 6 position the fragments heterylformazane or heterylhydrazone, with a pocket device for preconcentration.

New sorbents and indicator powders for preconcentration and determination of trace metals in liquid samples by E. Morosanova; A. Velikorodny; Y. Zolotov (pp. 305-308).
Two approaches to immobilize complex-forming analytical reagents (PAN, PAR, Xylenol orange, Brombenzothiazo, Crystal violet, Cadion, and Sulfochlorophenolazorhodanine) for the preparation of new sorbents and indicator powders are suggested: on-line coating of reversed-phase silica gel by reagents or doping of porous sol-gel silica with reagents. The retention of Ag, Cd, Cu(II), Co(II), Fe(III), Mn(II), Ni, Pb, and Zn on the sorbents developed was investigated. Quantitative sorption and desorption conditions were optimized. Procedures for the determination of Cd, Cu(II), Fe(III), Pb, and Zn with flame atomic absorption, spectrophotometric, and diffusion scattering spectrometric detection were elaborated. Detection limits for Cd, Cu(II), Fe(III), Pb, and Zn were 3 μg/L, 6 μg/L, 5 μg/L, 40 μg/L, and 1 μg/L, respectively. The procedures were used for the analysis of various real samples, e.g., natural and waste waters, and food.

Determination of weak acids by indirect potentiometry without titration by O. E. Ruvinskii; V. E. Akulinin (pp. 309-310).
The simple determination of the sum of weak (polycarboxylic) acids in aqueous solutions and titratable acidity of wines based on indirect iodate-iodide potentiometry without titration was described.

Voltammetric stripping analysis of metal concentrates with polymers soluble in aqueous solutions by E. A. Osipova; V. E. Sladkov; A. I. Kamenev; V. M. Shkinev (pp. 311-313).
The conditions were worked out for the simultaneous stripping voltammetric determination of components of the ternary Pb(II)-Cu(II)-Cd(II) and binary Ag(I)-Cu(II) systems at a carbon-paste electrode in 2% aqueous solutions of the water soluble polymer polyethyleneimine (PEI) and its thiourea-containing derivative (TU-PEI). Water-soluble polymers are shown to reduce the mutual effects of the components of the binary and ternary system at the electrode surface. The different complex stability of Ag(I), Pb(II) or Cd(II) and Cu(II) with PEI and TU-PEI allows Ag(I), Pb(II) and Cd(II) to be determined in the presence of a large excess of Cu(II).

Chromatographic determination of phenylarsenic compounds by R. Haas; Torsten C. Schmidt; Klaus Steinbach; Eberhard von Löw (pp. 313-318).
Gas chromatographic (GC) and liquid chromatographic methods for the investigation of phenylarsenic compounds are presented. With gas chromatography using an electron capture detector (ECD), the chemical warfare agents PFIFFIKUS, CLARK I and CLARK II can be detected. After derivatization with mercaptans and dimercaptans the sum of diphenylarsenic compounds resp. phenylarsenic and phenylarsonic compounds can be detected as the mercapto resp. dimercapto derivatives. High performance liquid chromatography (HPLC) analysis may be used for the detection of triphenylarsenic compounds and ADAMSITE.

In-situ methylation of strongly polar organic acids in natural waters supported by ion-pairing agents for headspace GC-MSD analysis by Peter L. Neitzel; Wolfgang Walther; W. Nestler (pp. 318-323).
Strongly polar organic substances like halogenated acetic acids have been analyzed in surface water and groundwater in the catchment area of the upper Elbe river in Saxony since 1992. Coming directly from anthropogenic sources like industry, agriculture and indirectly by rainfall, their concentrations can increase up to 100 μg/L in the aquatic environment of this catchment area. A new static headspace GC-MSD method without a manual pre-concentration step is presented to analyze the chlorinated acetic acids relevant to the Elbe river as their volatile methyl esters. Using an ion-pairing agent as modifier for the in-situ methylation of the analytes by dimethylsulfate, a minimal detection limit of 1 μg/L can be achieved. Problems like the thermal degradation of chlorinated acetic acids to halogenated hydrocarbons and changing reaction yields during the headspace methylation, could be effectively reduced. The method has been successfully applied to monitoring bank infiltrate, surface water, groundwater and water works pumped raw water according to health provision principles.

Determination of small quantities of nitrogen oxides in air by ion chromatography using a chromatomembrane cell for preconcentration by H. Erxleben; L. N. Moskvin; T. G. Nikitina; J. Simon (pp. 324-325).
Chromatomembrane (CM) cells operate in computer-aided FIA systems as unique manifolds for extraction and preconcentration procedures. By coupling with ion chromatography an instrumentation was obtained allowing sample preparation and detection of nitrogen oxides in air in a quick and automated way. The aim of this paper is to study the absorption of acid components from air inside the new devices.

Determination of metal-cofactors in respiratory chain complexes by total-reflection X-ray fluorescence spectrometry (TXRF) by A. Wittershagen; P. Rostam-Khani; V. Zickermann; I. Zickermann; S. Gemeinhardt; B. Ludwig; B. O. Kolbesen (pp. 326-328).
Total Reflection X-Ray Fluorescence Spectrometry (TXRF) offers many advantages for the detection of trace elements in enzymes as compared to other well known analytical techniques like flame-AAS or ICP-AES because of the significantly smaller amounts of sample required. Without any decomposition, elements like Fe, Ni, Cu, Zn, Mn and Mo could be determined with high accuracy, in spite of the large bio-organic matrix. Besides the metals also sulfur can be determined in protein samples. The two terminal oxidases, cytochrome c oxidase and quinol oxidase, isolated from the soil bacterium Paracoccus denitrificans, were transferred from their usual salt buffer into a solution of 100 mmol/L tris(hydroxymethyl)aminomethane (TRIS) acetate containing an appropriate detergent. By this procedure an improved signal/noise ratio is attained. The data for cytochrome c oxidase are in good agreement with values obtained by ICP-AES. Further results of quinol oxidase, which has different element ratios, also fit the expected values. The investigations lead to the conclusion that the method is well suited for the quantitative determination of metals in enzymes, and in particular their molar ratios, and requires only small amounts of the biological sample without any extensive pretreatment.

Development of an enzyme-linked immunosorbent assay for gentamicin in human blood serum by A. Y. Kolosova; A. N. Blintsov; J. V. Samsonova; A. M. Egorov (pp. 329-330).
An enzyme-linked immunosorbent assay (ELISA) for the quantitative detection of gentamicin in human blood serum was developed. Peculiarities of the adsorption on the microtitre plate surface of the gentamicin-protein conjugate were investigated. Different conditions of the competition stage of the analysis were studied and conditions for gentamicin monitoring in human blood serum in the clinical range were optimized. The matrix effect on the assay results, the specificity of the analytical system and the stability of the reagents were examined. The method permits gentamicin concentrations to be determined in human blood serum, diluted 1/1000, in the linear range from 1 to 30 ng/mL. The assay is characterized by high sensitivity (0.5 ng/mL), good reproducibility (CV < 12%) and good correlation with PFIA (r = 0.943).
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