New organosilicon derivatives of some analytical reagents: sorbents and metallochromic agents

A synthesis of organosilicon monomeric and polymeric derivatives of 1,4-phenylenediamine, 4-aminoantipyrine, and aniline, which are analytical agents possessing sorption properties, was accomplished. The synthesized organosilicon polymers were studied as sorbents of heavy metals Fe^III, Hg^II and noble metals Ag^I, Au^III, Rh^III, Pd^II, Pt^IV. Poly[(3-N-silsesquioxanylpropyl-4aminoantipyrine)] exhibited high sorption activity with respect to platinum group metals in comparison with poly[N,N´-bis(3-silsesquioxanylpropyl)-1,4-phenylenediamine]. The reaction of poly[(3-N-silsesquioxanylpropyl-4-aminoantipyrine)] practically with all the elements under study was accompanied by coloring. The starting monomer exhibited similar metallochromic properties.     

Modern aspects of toxicological analysis

The field of analytical toxicology has evolved from wet chemistry to one of complex instrumental methods. The combination of chromatography and mass spectrometry has provided particularly exciting possibilities.     

Synthetic aspects of the characterization of some silica-bound complexing agents

A number of synthetic aspects of silica-bound complexing agents are considered. Modifications of the procedure for amidization of bound amines and of the diazotizationcoupling sequence are discussed. The amidization of aminopropyl silica gel appears to be complete while that of ethylenediamine silica gel is less so. Loss of activity of the dried, bound diazonium salt appears to result from return to the Ar-NH₂ form, while a decrease in metal-ion complexation capacity for 8-quinolinol silica gel compared to the aminopropyl or ethylenediamine silica gel seems to be related to steric clogging of the matrix pores by bound organic moieties. A method of stripping the azo-coupled ligand from the appendage is examined, and some infrared and thermogravimetric characterizations are presented.     

Phytosterols and anabolic agents versus designer drugs

Cholesterol is a well-known component in fats of animal origin and it also is the precursor of natural hormones. Phytosterols appear in plants and only differ slightly in structure from cholesterol. An important difference however is the low absorption in the gut of phytosterols and their saturated derivatives, the phytostanols. As a result, there is time for all kind of reactions in faecal material inside and outside of the gut. Determination of the abuse of natural hormones may be based on gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Abuse of natural hormones changes the 13C/12C ratio of some metabolites during a relatively long time. The formation of (natural) hormones in the gut may interfere with this method. Designer drugs are mainly known from sports doping. In animal fattening, designer drugs may be used as well. Small changes in the structure of (natural) hormones may lead to a new group of substances asking for new strategies for their detection and the constatation of their abuse.     

Experimental studies on some aspects of toxicological effects of gas phase cigarette smoke (GPCS)

We have studied the toxicological effects of gas phase cigarette smoke (GPCS) on: 1) lecithin-formed liposome lipid peroxidation; 2) the liposomal membrane fluidity; 3) conformation changes of rat lung cell membrane proteins; and 4) respiratory burst of human polymorphonuclear leukocytes. The results of these investigations suggested that by stimulating lipid peroxidation, GPCS can cause changes of membrane fluidity and alterations of membrane protein conformations as well as damages to membrane-bound enzymes. We conclude that oxidative damage to cells and tissues is an important toxicological property of GPCS.     

Kinetic aspects of analytical chemistry

A broad view of the role of kinetics in analytical chemistry is presented. Two principal themes are that the role of kinetic methods is much greater than is generally acknowledged and that the most commonly used kinetic approaches make inadequate use of information that is available. After a brief discussion of historical developments that date back to the latter part of the 1800s, primary attention is focused on a classification of measurement and data-processing approaches that have been developed. Approaches are grouped into methods for single components without and with error compensation and methods for resolving two or more components in mixtures. They are further grouped into direct-computation and curve-fitting approaches and into integral and derivative methods within these more general categories. Correlations are then drawn between these approaches as applied to chemical processes and to physicochemical and purely physical processes such as luminescence, electrode responses, and flow systems, including chromatographic processes. It is argued that all analytical methods are either kinetic or equilibrium in character and that kinetic-based methods represent a much larger fraction of the total than is generally recognized.     

Polarography of proteins and its analytical aspects

A review of the polarography of proteins and its analytical aspects is presented.     

Philosophical aspects of modern analytical chemistry

Several important aspects are considered: the definition of analytical chemistry, the intercorrelation of this field and other sciences, the content of the theory of the discipline, and the internal structure of analytical chemistry. Attention is paid to the incentive for the development of analytical chemistry as a science. The ratio of basic and applied aspects is discussed. Finally the name of this branch of science is considered.     

LC-MS in analytical toxicology: some practical considerations

Liquid chromatography, coupled with single-stage or tandem mass spectrometry, is a powerful tool increasingly used in analytical toxicology. However, the atmospheric pressure ionization processes involved are complex, and subject to interference from matrix components, for example. Further, the techniques used in sample preparation, chromatography and mass analysis are developing rapidly. An understanding of the advantages and limitations of LC-MS ensures appropriate analyses are performed, and that reliable results are generated. Consideration should be given to the influence of the sample preparation and chromatographic conditions on the ionization of the analyte at the mass spectrometer interface. This review aims to provide some practical guidance and examples to aid method development for commonly encountered analytes in analytical toxicology.     

Arsenic contamination in groundwater: some analytical considerations

For countries such as Bangladesh with a significant groundwater arsenic problem, there is an urgent need for the arsenic-contaminated wells to be identified as soon as possible and for appropriate action to be taken. This will involve the testing of a large number of wells, potentially up to 11 million in Bangladesh alone. Field-test kits offer the only practical way forward in the timescale required. The classic field method for detecting arsenic (the 'Gutzeit' method) is based on the reaction of arsine gas with mercuric bromide and remains the best practical approach. It can in principle achieve a detection limit of about 10 mug l(-1) by visual comparison of the coloured stain against a colour calibration chart. A more objective result can be achieved when the colour is measured by an electronic instrument. Attention has to be paid to interferences mainly from hydrogen sulfide. Due to analytical errors, both from the field-test kits and from laboratory analysis, some misclassification of wells is inevitable, even under ideal conditions. The extent of misclassification depends on the magnitude of the errors of analysis and the frequency distribution of arsenic observed, but is in principle predictable before an extensive survey is undertaken. For a country with an arsenic distribution similar to that of Bangladesh, providing care is taken to avoid sources of bias during testing, modern field-test kits should be able to reduce this misclassification to under 5% overall.     

An amperometric nitrate reductase-phenosafranin electrode: kinetic aspects and analytical applications

The enzyme-catalysed reduction of nitrate was studied utilising Aspergillus niger nitrate reductase (NR) and phenosafranin in solution as the enzyme regenerator, working at lower potentials than that of the more common methyl viologen mediator. Cyclic voltammograms when enzyme, phenosafranin and substrate were together put in evidence the enzyme-catalysed reduction of nitrate, although with a relatively slow kinetics. From slope values not dependent on mediator concentration, the apparent Michaelis-Menten constant was evaluated. Analytical parameters for the enzyme-modified electrode in the presence of phenosafranin for the determination of nitrate content in water were assessed, including a recovery assay for nitrate added to a river water sample. The stability of the electrode was checked.     

Some aspects of analytical instrumentation: models, techniques, instruments

Summary The paper gives a review of investigations aimed at the development of instruments and techniques for analytical chemistry performed by the Institute for Analytical Instrumentation of the USSR Academy of Sciences. Advances in mass spectrometry of non-volatile labile compounds, determination of amino acid sequence in peptides, multidimensional Mössbauer spectroscopy, EPR recording optical techniques, microcolumn chromatography, field flow fractionation (FFF), and flow injection analysis (FIA) are considered.

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Einige Aspekte des analytischen Gerätebaus: Modelle, Verfahren, Instrumente

     

Isotopologs and isotopomers: New analytical aspects of isotopic mass spectrometry in biology

Metabolic products of biological systems in most cases are polyatomic molecular structures containing polyisotopic elements (hydrogen, carbon, nitrogen, oxygen, sulfur, chorine, etc.) that are different in genesis and biosynthetic pathways. In the molecules carrying two and more atoms of polyisotopic element in different positions (sites), the probability of detection of isotopes by sites in the pool (array) of analyzed molecules may be different, i.e., there is intramolecular isotopic heterogeneity by the specified element. Detection and quantitative estimation of isotopic heterogeneity of polyisotopic elements in molecules by the methods of isotopic mass spectrometry is a novel source of information about the processes involving the respective polyisotopic element. An isotopic equation has been proposed, the coefficients of which are normalized peak intensities of isotopically different molecular ions in the mass spectrum of the analyte. Solutions of this equation reflect the abundance ratios of isotopic atoms of polyisotopic element by its positions in molecules comprising the analyzed pool. During homogenous (equally probable) distribution of isotopic atoms of the element by all of its sites in molecules of the analyzed pool, solutions of the isotopic equation are equal to each other. In the case of non-homogenous isotope distribution of the polyisotopic element in the pool of molecules, solutions of the isotopic equation take on different values and may be presented by both real and complex numbers. Solutions of the isotopic equation reflect the peculiarities of distribution of element isotopes in a molecule and possible pathways of formation of a pool of analyzed molecules under laboratory and natural conditions.     

Macroreticular ion-exchange resins: some analytical applications to petroleum products

Extraction and subsequent recovery, in four separate fractions, of naphthenic acids, alkylphenols, pyrrollic compounds and nitrogen bases can be made from petroleum products using macroporous ion-exchange resins. Distinctive features of the technique are the use of dissolved gases in polar solvents as eluants and the application of the carbonate form of anion-exchange resins. The transition metal form of a macroreticular cation exchanger is shown to extract ligands from non-aqueous systems and a specific application to petroleum analysis is given.     

Comprehensive two-dimensional gas chromatography improves separation and identification of anabolic agents in doping control

The application of comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC × GC-TOFMS) for the analysis of six anabolic agents (AAs) in doping control is investigated in this work. A non-polar–polar column configuration with 0.2 μm film thickness (d_f) second dimension (²D) column was employed, offering much better spread of the components on ²D when compared to the alternative 0.1 μm d_f²D column. The proposed method was tested on the “key” AA that the World Anti-Doping Agency (WADA) had listed at the low ng mL⁻¹ levels (clenbuterol, 19-norandrosterone, epimethendiol, 17α-methyl-5α-androstane-3α,17β-diol, 17α-methyl-5β-androstane-3α,17β-diol and 3′-OH-stanozolol). The compounds were spiked in a blank urine extract obtained by solid-phase extraction, hydrolysis and liquid–liquid extraction; prior to analysis they were converted to the corresponding trimethylsilyl (TMS) derivatives. The limit of detection (LOD) was below or equal to the minimum required performance limit (MRPL) of 2 ng mL⁻¹ defined by WADA, and the correlation coefficient was in the range from 0.995 to 0.999. The method allows choosing an ion from the full mass spectra which shows the least interference from the matrix and/or the best sensitivity; this can only be done if full scan mass spectral data are available. The advantage of GC × GC over classical one-dimensional GC (1D GC), in terms of separation efficiency and sensitivity, is demonstrated on a positive urine control sample at a concentration of 5 ng mL⁻¹. The obtained similarity to the in-house created TOFMS spectra library at this level of concentration was in the range from 822 to 932 (on the scale from 0 to 999). Since full mass spectral information are recorded, the method allows the retro-search of non-target compounds or new “designer steroids”, which cannot be detected with established GC–MS methods that use selected ion monitoring (SIM) mode.