Search

A procedure was developed for determining chromium(VI) in the soil organic fraction; it consisted of three steps: the preparation of a soil solution; the isolation and separation of chromium(VI) and chromium(III); and the determination of chromium(VI). Soil solutions were prepared by leaching soil samples with a Na4P2O7 solution (the Rudd method). Chromium(VI) was extracted from the soil solution with a solution of sodium diethyldithiocarbamate in n-amyl alcohol; the conditions of the extraction and separation of chromium(VI) and chromium(III) were optimized. Chromium(VI) in solutions was determined after back extraction by spectrophotometry with diphenylcarbazide or by flame atomic absorption spectrometry. The procedure was validated using a reference soil sample, and the material balance of chromium in the systems under study was calculated. [ABSTRACT FROM AUTHOR]

The composition of vodkas, rectified food alcohols, cognacs, cognac spirits, and other strong alcoholic beverages was studied by chromatography and compared with the composition of industrial (synthetic and hydrolysis) ethyl alcohols, adulterated cognacs, and homemade spirits (samogon) from the illicit market. It was found that the majority of the test alcohol-containing liquids were close to commercial alcoholic beverages in terms of chemical composition and toxic properties. The samples containing ethylene glycol and enriched components of the head fraction of rectification should be considered most toxic. [ABSTRACT FROM AUTHOR]

A procedure for distinguishing synthetic ethyl alcohols from those obtained by fermentation using gas chromatography-mass spectrometry is discussed. To reveal the nature of alcohols, the following special chemical markers (characteristic components of the impurity composition of synthetic alcohol) are used: 2-butanol, acetone, and crotonaldehyde. It was found that 2-butanol is the most informative marker of synthetic alcohol because it is not present in fermentation alcohols. Acetone and crotonaldehyde are additional markers of synthetic alcohol because they can occur in food alcohols. The results of studying the stability of the above impurity components and crotonaldehyde degradation products are presented. [ABSTRACT FROM AUTHOR]

To improve the reliability and information content of the quality control of cognacs and cognac spirits and to detect the signs of adulterated products, quality tests and methods for the instrumental analysis of cognacs and brandies by gas chromatography, high-performance liquid chromatography, gas chromatography-mass spectrometry, and UV-VIS spectrophotometry are considered. A set of marker substances, the concentrations of and ratios between which allow one to detect various types of adulterations and violations in manufacturing processes, was determined and methodologically substantiated. The marker substances were tentatively subdivided into several groups: volatile components, which are characteristic of cognac and affect its organoleptic properties; oak-wood substances, which are accumulated in cognac spirit in the course of aging; flavoring components; denaturing agents; and other substances that are uncharacteristic of cognac. Particular kinds of cognac products were experimentally examined, and the most characteristic types of adulterations and technological violations in the manufacture of both domestically produced and imported cognac products were exemplified. Recommendations on the effective quality control of cognac products are given, and a high level of identification methods in use is noted. [ABSTRACT FROM AUTHOR]

The interaction of primary aromatic amines (PAAs) with 4-dimethylaminocinnamaldehyde (DMACA) is studied in various media by UV, IR, and 1H NMR spectroscopy. The optimum conditions for these reactions have been found, and the reasons for better analytical effects in the condensation reaction of PAAs with this reagent have been revealed. The physicochemical properties of the analytical form are studied using the aniline–DMACA model system as an example. A correlation has been found between the pHopt of the reactions under study and the pKa values of arylamines. [ABSTRACT FROM AUTHOR]

The use of gas chromatography (GC), gas chromatography–mass spectrometry (GC–MS), and UV–VIS spectrophotometry for identifying the falsification of strong alcoholic beverages (vodka, gin, cognac, and whiskey) was considered. In the GC analysis of ethyl alcohol and vodkas based on it, the test alcohol was assigned to synthetic alcohol or to biochemically produced alcohol using a set of typical impurities, markers of the alcohol nature, which present in the test alcohol in a certain ratio and can be determined by GC or GC–MS analysis. The multicomponent analysis of cognacs and related liquors can reveal the replacement of cognac spirit with alcohol produced from nongrape raw materials, to determine whether the cognac spirit was in contact with oak wood and how long was the duration of its aging, and to detect the falsification of the age by adding certain ingredients. The limitations of chromatographic and spectrometric analytical techniques in the identification of adulterated alcoholic beverages was demonstrated. The validation criteria for testing the identification of alcoholic beverage components by chromatographic techniques received special attention. [ABSTRACT FROM AUTHOR]

An atomic absorption spectrometric method for the determination of trace amounts of nickel after adsorption of its 1 -(2-pyridylazo)-2-naphthol complex on microcrystalline naphthalene has been developed. This complex is adsorbed on microcrystalline naphthalene in the pH range 4.5-7.8 from large volumes of aque ous solutions of various alloys and biological and environmental samples containing nickel. After filtration, the solid mass consisting of nickel complex and naphthalene was dissolved in 5 mL of dimethylformamide, and the metal was determined using a flame atomic absorption spectrometer at a wavelength of 232 nm. Alternatively, nickel can be quantitatively adsorbed on [l-(2-pyridylazo)-2-naphthol]-naphthalene adsorbent packed in a column and determined similarly. The calibration curve is linear over the concentration range 2.0-100 Μg of nickel in 5 mL of the final dimethylformamide solution. Eight replicate determinations of 20 Μg of nickel give a mean absorbance of 0.072 with a relative standard deviation of 1.3%. The sensitivity for 1% absorption is 0.24 Μg/mL. Various parameters such as the effect of pH, the volume of the aqueous phase, and the interference of a large number of metal ions with the determination of nickel have been studied in detail to optimize the conditions for its determination in various standard alloys and biological and environmental samples. [ABSTRACT FROM AUTHOR]

Abstract -- Molybdenum was quantitatively extracted form large volumes of aqueous solutions of various samples by 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) and tetradecyldimethylbenzylammonium chloride (TDBA) on microcrystalline naphthalene in the pH range [...]