Mikhail Zayats - Academia.edu (original) (raw)

Papers by Mikhail Zayats

Journal of Food Composition and Analysis

Journal of the Belarusian State University. Chemistry

The extraction of anabolic steroids (1,4-androstadiene-3,17-dione; 17α-methyltestosterone; 19-nor... more The extraction of anabolic steroids (1,4-androstadiene-3,17-dione; 17α-methyltestosterone; 19-norethiocholanolone; 4-hydroxytestosterone; 4-androstene-3,17-dione; 5α-androstane-3β,17β-diol; dehydroepiandrosterone; calusterone; clostebol; methandienone; methyldienolone; nandrolone; testosterone; epitestosterone; tibolone; 19-norandrostenedione; 1-methylene-5α-androstan-3α-ol-17-one) by aqueous-organic mixtures from hexane solutions was studied at the temperature (20 ± 1) °C. Based on the experimental data obtained, the partition ratios of anabolic steroids were calculated, which were used to optimise the standard sample preparation procedure in the process of determining the compounds under study in biologically active dietary supplements and specialised sports nutrition. It was found that the most effective and selective extractants from hydrocarbon solutions are water-acetonitrile mixtures containing from 10 to 20 % by volume of water. An extraction technique has been developed for...

Journal of Chemical Metrology, 2021

A quality control material (QCM) for the analysis of volatile compounds in alcoholic beverages wa... more A quality control material (QCM) for the analysis of volatile compounds in alcoholic beverages was developed. The problems of the development and production of QCM were investigated. The seven water-ethanol solutions, containing 9 volatile compounds (acetaldehyde, methyl acetate, ethyl acetate, methanol, propan-1-ol, propan-2-ol, 2-methylpropan-1-ol, butan-1-ol and 3-methylbutan-1-ol) with a concentration range from 1.20 to 5000 mg/L of anhydrous ethanol were prepared and studied according to the ISO Guide 80 and ISO Guide 35 in order to prove their stability over 6 months. The algorithm for the assessment of uncertainty associated with the characterization of QCM was developed. The studies were carried out by validated direct gas chromatography (GC) method with flame ionization detection (FID), based on using ethanol as an internal standard. The expanded relative uncertainty of QCM does not exceed 4.5 %.

The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rape... more The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed 27 oil (or oil solution in hexane)/organic solvents has been studied at 20 ± 1 C. The distribution constants

Аналитика и контроль, 2019

Journal of the Belarusian State University. Chemistry, 2018

Optimal conditions for the extraction of halauxifen-methyl from grain, straw and green mass of ba... more Optimal conditions for the extraction of halauxifen-methyl from grain, straw and green mass of barley; seeds, oil and green mass of rape, as well as the conditions for the purification of extracts were selected on the basis of the distribution constants (P) and distribution coefficients (D) experimentally determined at a temperature of (20 ± 1) °C. At the first stage, acetonitrile, or acidified acetonitrile, or a mixture of water and acetonitrile were used to extract the pesticide. Halauxi fen-methyl was found to be a weakly hydrophobic substance and it exhibits the properties of a weak base in aqueous solutions. For the purification of plant material extracts hexane – 1 mol/L aqueous solution of hydrochloric acid and hexane – 10 % K2HPO4 aqueous solution were successfully used (to neutralize the acid and increase the extraction constant due to the salting out effect). The samples obtained after purification are sufficiently pure. So, the residual amounts of halauxifen-methyl can be...

Journal of the Belarusian State University. Chemistry, 2019

Based on the literature data on the solubility of pymetrozine in water and organic solvents, as w... more Based on the literature data on the solubility of pymetrozine in water and organic solvents, as well as experimental data on the extraction of pymetrozine from water, soil and plant matrices, the optimal conditions for the extraction of pymetrozine from water; soil; cucumber; rape seeds, oil and green pods were selected. The conditions for cleaning extracts were selected as well. At the first stage, acetonitrile, a mixture of dichloromethane – isopropanol, or a mixture of dichloromethane – methanol in the presence or absence of inorganic salts were used for extraction of the pesticide. Pymetrozine was found to be a highly hydrophilic substance. For the purification of extracts of pymetrozine from plant matrices the extraction systems hexane – 0.02 mol/L aqueous solution of orthophosphoric acid, hexane or chloroform – aqueous solutions of ammonium sulfate were successfully used. The samples, obtained after this treatment, were pure enough to determine the residual amounts of pymetroz...

Analytical Chemistry Research, 2015

The distribution of 19 azole class pesticides in hexane/aqueous-organic mixtures systems and rape... more The distribution of 19 azole class pesticides in hexane/aqueous-organic mixtures systems and rapeseed oil (or oil solution in hexane)/organic solvents has been studied at 20 ± 1°C. The distribution constants (P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied pesticides are hydrophobic, i.e., in hexane-water system log P) 0. Replacement of water by organic solvents results in sharp log P falling, and their values become negative. It is revealed that solutions of strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in 50-2000 times for the majority of the studied pesticides. This phenomenon was used for the development of the improved technique for the quantitative analysis of a widely used azole class pesticides, which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate, and final GC-ECD (gas chromatography with electron capture detection) determination of azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below 10%. The obtained limits of quantitation, ranged from 3.0 to 300 lg kg À1 , are below the maximum residue levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully applied to different rapeseed oil samples.

Food Additives & Contaminants: Part A, 2016

ABSTRACT The distribution of 40 pesticides of basic nature in different extraction systems was st... more ABSTRACT The distribution of 40 pesticides of basic nature in different extraction systems was studied at 20 ± 1°C. The distribution constants (P) and distribution ratios (D) between n-hexane and polar phases are calculated. It was found that the studied pesticides are most fully and selectively extracted from hexane and vegetable oils by solutions of perchloric acid in acetonitrile. In particular, the acidification of acetonitrile decreases the D-value of fenpropimorph by 29,000 times. This phenomenon was used for the development of an improved technique for the quantitative analysis of widely used pesticides of basic nature in rapeseed, linseed, sunflower and olive oils by GC-MS. The proposed approach allows obtaining much purer sample extracts, compared with the use of standard solvent extraction with further purification by the freezing-out technique. This approach expands the range of pesticides (flutriafol, fenpropidine, metazachlor, cyprodinil and others) that can be determined by GC-MS. The recovery values of the studied pesticides from vegetable oils were between 85% and 115% with RSD values below 10%. The obtained limits of detection ranged from 0.001 to 0.1 mg kg–1, and are below or equal to the maximum residue levels (MRLs) set by the European Union for the corresponding pesticides. GRAPHICAL ABSTRACT

Russian Journal of Physical Chemistry A, 2012

The distribution of model oxygen containing organic nonelectrolytes in n hexane-aqueous solu tion... more The distribution of model oxygen containing organic nonelectrolytes in n hexane-aqueous solu tions of mineral salts (KF, (NH 4) 2 SO 4 , K 2 CO 3 , K 3 PO 4) and lower alcohol-saturated aqueous solutions of salt (KF, K 2 CO 3 , K 3 PO 4) systems are studied at a temperature of 20 ± 1°C. Increments of the methylene and functional groups of organic nonelectrolyte of partition constants logarithm are calculated. It is shown that the nature of the salting out effect primarily involves strengthening of the salt solution's structure and growth of the methylene group increment. A comparative characteristic of various salts according to the degree of their structuring effect and the effectiveness of the salting out of organic nonelectrolytes from aqueous solu tions is given.

Journal of Analytical Chemistry, 2008

ABSTRACT The distribution of ethanol and butanol between n-hexane and aqueous solutions of ammoni... more ABSTRACT The distribution of ethanol and butanol between n-hexane and aqueous solutions of ammonium sulfate at 20 ± 1°C was studied over an ideal concentration region of the substances in the organic phase. The distribution constants of the substances and the increments of the methylene and hydroxyl groups of the alcohols in the logarithm of the distribution constant were calculated. It was found that an increase in the salt concentration in the aqueous phase resulted in a considerable increase in the increment of the methylene group and significantly improved the alcohol separation efficiency. The dependence of the distribution coefficients of ethanol and butanol on the concentration of ethanol in the aqueous phase was studied. A dramatic decrease in the increment of the methylene group was found as the ethanol concentration in the salt phase was increased above 4.5 vol %. A procedure was developed for extraction sample preparation for the subsequent determination of the characteristic components of cognac products and for the authentication of these products by gas chromatography. The essence of this procedure consists in the hexane extraction of butanol and other hydrophobic substances from cognac product samples prediluted with an aqueous solution of ammonium sulfate. In this case, the major portion of ethanol, as well as hydrophilic and thermally unstable impurities, which complicate analysis with direct sample injection, remained in the salt solution. The procedure was tested with 16 samples of cognac and cognac spirits from Georgia, including both authentic and adulterated products.

Analytica Chimica Acta, 2013

h i g h l i g h t s • The extraction of 150 pesticides in different systems has been investigated... more h i g h l i g h t s • The extraction of 150 pesticides in different systems has been investigated. • The highest and most scattered values of Lg P are observed in hexane/water system. • The minimal and leveled values of Lg P are observed in hexane/acetonitrile system. • Conditions of pesticides separation and recovery are estimated on the basis of Lg P.

Journal of the Belarusian State University Chemistry, 2017

The distribution of a number of organophosphorus pesticides of different classes (phosphates, thi... more The distribution of a number of organophosphorus pesticides of different classes (phosphates, thiophosphates, dithiophosphates, phosphonothioates, phosphonodithioates, phosphoramidates, phosphoramidothioates) was studied at 20 ± 1 °C in extraction systems hexane – water, hexane – ethylene glycol, hexane – acetonitrile, hexane – a mixture of acetonitrile and water and hexane – a mixture of acetonitrile and ethylene glycol. The distribution constants (P) of the pesticides and the values of the functional groups increments (If) between hexane and the polar phase were calculated. The factors that affect these values are discussed. The possibility of prediction of change of the pesticide distribution constants at introduction or replacement of one functional group to another is considered on the basis of the principle of additivity of Gibbs energy of distribution, or the method of group increments. The factors affecting the deviation of the calculated distribution constants of substances...