Vol 72, No 9 (2017)

The review is devoted to the consideration of adsorption preconcentration of synthetic anionic food dyes for their subsequent determination in various samples. The main classes of adsorbents and their features, conditions for extraction and desorption of the compounds to be determined in batch and dynamic modes, characteristics of procedures using adsorption preconcentration, and examples of their application to the determination of dyes in various food products are given.

Determination of the total concentration (с_Σ) of similar organic compounds as an total index (TI), expressed in terms of a standard substance of X_st, is a widely used but poorly studied type of chemical analysis. The main problem is the inaccuracy of estimate с_Σ. The article considers reasons for the appearance of systematic errors, rules of formation of groups of simultaneously determined compounds, and the choice of X_st. A classification of TI taking into account the nature of X_st is proposed. To improve the accuracy of analysis, it is expedient to simultaneously use of several standards and construct multivariate calibration dependences.

Magnetite nanoparticles coated with silica and hydrophobic octadecyl layers were successfully synthesized and used in magnetic solid phase extraction of tetracyclines from water samples. The magnetite nanoparticles facilitated a convenient magnetic separation of sorbent from an aqueous sample, the octadecyl layer helped to enhance the adsorption ability and the silica layer helped to prevent the aggregation of the magnetite nanoparticles. The effect of various parameters on the extraction efficiency were optimized including the amount of sorbent, sample pH, stirring rate, extraction time and desorption conditions. Under the optimum conditions, the recoveries were in the range of 82 to 88%, the calibration curves were linear over the concentration range of 0.002 to 1.0 μg/mL for oxytetracycline and 0.01 to 1.0 μg/mL for tetracycline and chlortetracycline, respectively. The developed method had several advantages such as simplicity, convenience, cost-effectiveness and high extraction efficiency.

This paper proposes a total phenolic acid estimation technique for samples with unknown phenolic acid composition and preliminary sample screening in resource-constrained settings. Phenolic acids constitute one of the important secondary metabolites for industry and researchers, but appropriate technique for its estimation by rural entrepreneurs is unclear. This study compared spectrophotometric Arnov test (AT) and potassium iodate test (PT) on the basis of seven parameters namely input requirements, process, limit of detection (LOD), limit of quantification (LOQ), linearity range, interferences and different phenolic compounds response. As per the results of the study PT is better than AT in input requirements, process, interference and different phenolic compounds response whereas AT is better than PT in LOD, LOQ and linearity range. Therefore, the study concluded that PT could be more suitable for rural entrepreneurs.

For aromatic amine determination in workplaces, stabilities of six types of carcinogenic aromatic amines (2,4-diaminotoluene, 4,4'-diamino-3,3'-dimethyldiphenylmethane, o-tolidine, 3,3'-dichlorobenzidine, 4,4'-methylenebis(2-chloroaniline), and o-dianisidine) were evaluated with air or argon gas bubbling for 45 min in aqueous solution under light irradiation (desk lamp) and heating conditions. Gas chromatography–mass spectrometry (GC–MS) was used to identify and quantify the aromatic amines. The following conditions were selected: temperature program 70°C (1 min), 7 grad/min up to 120°C (1 min), 10 grad/min up to 300°C (5 min), carrier gas flow rate 1.0 mL/min. 3,3'-Dichlorobenzidine concentration decreased by approximately 10% after irradiation with a desk lamp for 45 min in distilled water, and a monochloro compound was detected by GC–MS. The other aromatic amines were rarely different from the 0-min concentration. The shielding prevented the decomposition of 3,3'-dichlorobenzidine in distilled water.

Polyaromatic hydrocarbons in samples of thermally treated petroleum products and thermal destruction products of organic materials of various origins are studied. Samples of kerosene, diesel fuel, and gasoline of different grades, that is, light flammable petroleum products often used as combustion initiators; wood; flooring (linoleum); and offset paper are selected as test samples. A pattern for determining these samples by chromatography–mass spectrometry against the background of other products formed under fire conditions is developed. It is suggested to use the limiting value of the intensity ratios of the peaks of tri- and bicyclic condensed arenes in trace residues of the combustion initiator, modified as a result of evaporation and burnup, as an identification parameter. This approach expands the range of tasks in identifying the source of environmental pollution and in determining traces of combustion initiator for forensic and fire-technical expertise.