Zhurnal Analiticheskoi Khimii

The possibility to identify and establish the fact of turmeric adulteration by simple and affordable methods using methods of infrared spectroscopy, digital colorometry and chemometric processing of spectral data was shown. Near-infrared spectroscopy was used to differentiate between samples of turmeric powder purchased in India, made by grinding the roots, and commercial samples, and to separate them from samples with impurities of flour, starch, breadcrumb and chalk by analyzing diffuse reflectance spectra using principal component methods, hierarchical cluster analysis and formal independent class analogy modeling. The same approaches were applied to the simpler and less costly colorometric method. Chemometric processing of the obtained data confirmed the lack of similarity of the analyzed turmeric samples with samples containing additives and allowed the determination of impurities using multivariate regression analysis algorithms. Comparison of the results obtained by IR spectroscopy and digital colorometry showed their equivalent efficiency, which allowed us to recommend the more affordable colorometric method for routine quality control and detection of turmeric adulteration.

For trinitrotoluene isomers by gas chromatography-mass spectrometry (GC-MS), the processes of chromatographic separation and formation of negative ion (NI) mass spectra in the mode of resonant electron capture, implemented by a minimal technical modification of the domestic serial GC-MS complex “Chromatech-Crystal”, were investigated and compared with the basic mode of positive ions (PI) under electron ionization. The chromatographic retention time of the isomers was found to increase in direct proportion to the dipole moment of the molecules, illustrating the significance of intermolecular dipole interactions between polar molecules of the analyte and the stationary phase. It is shown that the chromatograms of full current OI, which are recorded at fast constant scanning of ionizing electron energy in the low-energy range of 0-10 eV, well reflect the component composition of the analyzed sample, and the integral mass spectra of OI are characteristic and selective to isomers, being complementary in informativeness to the standard mass spectra of PI. This is due to the predominance of nitro-nitrite rearrangements and simple C-NO₂bond breaking at negative ionization over H-shift reactions, which dominate in the formation of PIs from TNT isomers.

The atmospteric pressure laser plasma ionization (APLPI) method in combination with machine learning methods is investigated to solve the problem of classification of vegetable oils. Samples of olive oil, rapeseed oil, sunflower oil and linseed oil were studied. The samples were classified on the basis of mass spectrometric profiles of volatile organic compounds emitted by the oils. It was shown that when hierarchical cluster analysis (HCA) with pre-selection of features by analysis of variance (ANOVA) and reduction of the dimensionality of the response matrix by t-distributed stochastic neighbor embedding (t-SNE), each type of oil forms a distinct cluster. Using the example of olive and rapeseed oil blends analysis, it was demonstrated that the combination of the APLPI method with the multiple linear regression (MLR) method allows to quantify the share of oils in the studied blends. The developed approach allows for rapid, direct nondestructive analysis of vegetable oils without sample preparation and can be used for detection of adulterated products.

Hyper cross-linked polystyrene was proposed for purification of extracts after sample preparation by QuEChERS method using multicomponent dispersive solid-phase extraction for determination of 19 pesticide residues in wheat grain by gas chromatography with tandem mass spectrometric detection. Sample preparation included extraction with water and acetonitrile and further purification of the extracts using hyper cross-linked polystyrene. The method provided quantitative separation of pesticides (degrees of separation ranged from 66 to 100 %). Pesticides were identified by selected transitions in multiple reaction monitoring mode. Determination was carried out by matrix graduation method and the limits of detection and determination were 0.03–0.3 and 0.1–1.0 µg/kg, respectively. The analysis of contaminated wheat samples showed that the results satisfactorily coincide with the data obtained by the classical QuEChERS method for determination of pesticide residues in agricultural products.

The article reveals the role of the Laboratory of Plant Anatomy and Physiology of the Academy of Sciences created by Academician A.S. Famintsyn in the birth and development of the idea of the chromatographic method of analysis by M.S. Tsvet in 1897– 1901. On the basis of previously unknown documentary and other materials it is established that M.S. Tsvet in fact discovered chromatography in 1901, and not in 1903, as it is commonly believed, and not in Warsaw, but in St. Petersburg, and in many respects thanks to the assistance of the academic community and first of all academician A.S. Famintsyn. The data on the establishment and activities of the Laboratory, on the life and creative pursuits of M.S. Tsvet in St. Petersburg, on his communication with colleagues and on the attitude of the Academy of Sciences staff to his works are presented.