The article is devoted to the development of a simple chromatographic method for the simultaneous determination of the well-known antiseptics – chlorhexidine and triclosan – in new generation of antiseptic liquids. The dependences of the retention times of chlorhexidine and triclosan on the acetonitrile concentration in the mobile phase (from 30 to 60%) and pH (in the range of 3–8 units) for sorbents Luna C18, Nucleosil CN, Diaspher C4 were studied. A perfect separation of chlorhexidine, p-chloraniline (the most toxic product of chlorhexidine decomposition), dibutylphthalate (as a component of cosmetic alcohol), triclosan and ionol (butylhydroxytoluene, BHT, E321 – antioxidant agent) during 20 minutes in the gradient elution mode on the column with a domestic sorbent Diaspher C4 has been demonstrated.

One of the most important directions of the development of pharmacological science is the development and introduction into clinical practice of medicines of natural and synthetic origin. A striking representative of domestic cytoprotectors is malic acid salt. 3-hydroxy-6-methyl-2-ethylpyridine, patented under the trade name "Ethoxidol". It is not inferior, and sometimes surpasses similar drugs in its pharmacological activity. Only one work has been found in the literature devoted to the determination of ethoxidol in medicinal preparations by voltammetry. Sensitivity is not sufficient for its determination in blood plasma. It was necessary to develop a more sensitive and selective method. Microemulsions are often used in variants of capillary electrokinetic chromatography or sample preparation, but the method of microemulsion liquid chromatography (MLC) has not been so widely used. The method has certain advantages over HPLC. In this work, the determination of ethoxidol in blood plasma was carried out by high-performance microemulsion chromatography with fluorimetric detection. 300 mm3 microemulsions were added to 300 mm3 of plasma and thoroughly mixed to precipitate plasma proteins. The addition of microemulsion prevents the co-deposition of ethoxidol together with proteins. The filler fluid was taken and injected into a chromatograph. The degree of extraction was controlled chromatographically by adding a known amount of ethoxidol to the extract from the blank plasma. In a micellar medium, substances can be solvated differently than in aqueous methanol/acetonitrile solutions. Changes in the spectral characteristics of substances are caused by the presence of oil in the composition of the microemulsion, the introduction of substances into a drop of which leads to a spectral shift. When determining ethoxidol, the excitation and detection wavelengths of λex 287 nm and λem 399 nm, respectively, were selected. It should be emphasized separately that the microemulsion additionally allows you to stabilize the components being determined. Thus, in the case of determination of ethoxidol in blood plasma, standard methods of sample preparation (liquid and solid-phase extraction, precipitation of proteins with organic solvents, acids, metal ions) did not lead to the desired result. In the case of dilution of the sample with microemulsion, the extraction was quantitative. The calibration dependence was linear in the concentration range 0.1-10 mg/dm3. The graph is described by the linear equation S=23.97C-1.257. The correlation coefficient R2=0.998. The detection limit is 50 micrograms/dm3. The relative standard deviation of S(r) is 0.08 (n=3). Thus, a new chromatographic method for determining ethoxidol in human blood plasma is proposed. It is shown that the use of microemulsion as an eluent leads to the stabilization of the drug in solutions and a significant increase in the extraction of ethoxidol from real samples.

The possibility of using a new graphene-based carbon monolith for searching new oil deposits or branches adjacent to the already registered oilfields by areal geochemical survey is demonstrated. The material has been developed at the Faculty of Chemistry of M. V. Lomonosov Moscow State University. Sorption of volatile organic compounds (VOCs) from soil air at the oilfield was carried out using two sorbents (carbon adsorbent and Tenax-TA traditionally used for such analyses) with subsequent determination by gas chromatography with mass spectrometric detection and thermal desorption as a way of sample injection (TD/GC/MS). The new material absorbs more hydrocarbons (n-alkanes and monoaromatics) in the range from C8 to C16 than Tenax-TA, the intensities of the chromatographic peaks of the compounds also being higher. The phenomenon of irreversible sorption from carbon materials is observed for VOCs from C17 and more. However, the concentration of such substances in the soil air is rather low due to the low pressure of saturated vapors of these compounds under normal conditions. Hence, the chromatogram of carbon monolith reflects the macro-characteristics of this oil deposit better than Tenax-TA. To increase the sensitivity of the determination, a preliminary optimization of thermal desorption conditions was carried out. The values of the helium flow rate through the sorbent sample and the desorption time of the compounds are chosen to get the largest peak area. The regeneration of sorbent samples is carried out to provide the possibility of their reusage. Tenax-TA decomposes at lower temperatures compared to carbon sorbent and thus cannot be purified completely unlike the new monolith. The graphene-based sorbent is reusable and much cheaper in the manufacture than imported polymer Tenax-TA since it is made of domestic materials.

The work is devoted to the search for conditions for the sample preparation and determination of carbamazepine and oxcarbazepine and identification of the products of their metabolism and degradation in human liver (post mortem) and material evidences by gas chromatography–mass spectrometry. A QUECHERS approach was developed to the sample preparation of carbamazepine and oxcarbazepine. Amitriptyline was proposed as an internal standard. Degradation products of carbamazepine and oxcarbazepine were studied in model solutions upon alkaline and acid hydrolysis and oxidation; 14 metabolites and degradation products were identified. The main analytical characteristics of the developed procedure were determined. The limits of detection are 0.1 and 0.2 µg/g for carbamazepine and oxcarbazepine, respectively. The developed procedure complies with the Validation Guidelines of the Russian Center for Forensic Medical Examination.

The effective mineralization of nitrofurazone (10–100 mg L−1) was performed in aqueous solutions in the presence of chloride ions by electrochemical treatment. The destruction of the organic pollutant molecules was due to their interaction with active oxygen- and chlorine-containing species forming at the inert anode (Pt/Ti or BDD) during electrolysis. Measurements of nitrofurazone concentration, chemical oxygen demand (COD) and total organic carbon (TOC) were used to estimate the removal efficiency of the pollutant. Both the pollutant oxidation rate and the degree of its mineralization were higher for the BDD anode due to the higher anode potentials on it in the course of electrolysis, which provides a high rate of active oxidizer species generation. As a result, practically full nitrofurazone molecule destruction (>99%) was achieved in 30 min at an anodic current density of 0.1 A cm−2, a volume current density of 1.33 A L−1 and pH 2 using BDD anodes. On the other hand, the nitrafurazone degradation efficiency was about 95% for Pt/Ti anodes under the same conditions. Additionally, byproducts of nitrofurazone electrooxidation were investigated by means of liquid chromato-mass-spectrometry (LC/MS). It was found that the initial decolorization of nitrofurazone solution, which occurs during the first 5 min of electrolysis, is due to the formation of a dichloro derivative of nitrofurazone, which causes the destruction of the π−conjugated bond system. Further electrolysis resulted in the almost complete destruction of the dichloro derivative within 30 min of electrochemical treatment.

A domestic composite material based on silicon carbide and nitrile butadiene rubber was used to identify volatile substances of banana, banana flavor, and creamy chewing candies by passive adsorption in combination with thermal desorption GC–MS. This method can be used to determine a wide range of compounds, for example, esters of carboxylic acids, terpenoids, aldehydes, aromatic hydrocarbons, alkanes, heterocyclic compounds, phenols, glycerides, and fatty acids. The obtained chromatographic profiles of the samples were compared. In the chromatogram of “Banana” flavor, five peaks (out of eight) corresponded to the compounds that form the aroma of a banana, and in the chromatogram of “Love is” candies with banana flavor, three corresponding peaks (out of 21) were found.

The possibility of improving the detection of 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) by HPLC-SPD under preliminary derivatization with 2-nitrobenzaldehyde (2NBA) and 4‑nitrobenzaldehyde (4NBA) in water with micellar catalysis is studied. The conditions for the derivatization of UDMH (pH, concentrations of reagent and surfactant, temperature, and reaction time) are optimized. The derivatization reactions proceed completely at pH 9 in the presence of 87 mM sodium dodecyl sulfate (SDS) solution and an excess of reagents at room temperature for 45 and 30 min for 2NBA and 4NBA, respectively. Quantitative yield of the reaction products, which is found by the absence of UDMH in the reaction mixture with ion chromatography, is achieved under these conditions. The micellar catalysis allows derivatization under milder conditions and provides the completeness of the reaction under low UDMH concentrations, which expands the linear range of the concentrations determined. A ZORBAX Eclipse Plus C18 chromatographic column (150 × 3.0 mm × 3.5 μm) was used for HPLC-SPD detection of UDMH, and a mixture of acetonitrile and 10 mM ammonia buffer solution at pH 7 (50/50, vol %) at a flow rate of 0.7 mL/min in isocratic mode was used as a mobile phase. The 2NBA and 4NBA dimethylhydrazones were detected at the wavelengths of 308 and 394 nm, respectively. The detection limits for UDMH ( S / N = 3) were 3 and 1.5 μg/L for 2NBA and 4NBA, respectively. The chromatographic analysis time was 15 min. The method developed for water analysis provides a simple, sensitive, and reproducible detection of UDMH in the concentration range of 5–1000 μg/L by the HPLC-SPD method without additional concentration.

A monolith based on foamed graphite is used for the sorption of hydrocarbons (alkanes, cycloalkanes, arenes) as markers of oil pollution. This material is patented by chemical engineers from the Department of Chemistry of the Moscow State University. It is shown that absorbed compounds can be determined qualitatively and quantitatively by GC/GC/MS with a thermal desorption system.

Adsorbents used to analyze air for concentrations of various organic compounds with their subsequent determination by thermal desorption gas chromatography–mass spectrometry (GC–MS) are considered. Tenax-TA is the most commonly used material for such tasks, but it has drawbacks. The characteristics of adsorbents of Tenax, Carbosieve, Carboxen, Carbotrap, Capbopack, Porapak, Chromosorb families, XAD polymer resins, activated carbons, and some monolithic carbon materials are given. Their advantages and disadvantages for the adsorption/thermal desorption of hydrocarbons are discussed. The advantages of monolithic carbon materials and the need in the development of a new domestic material for analytical gas chromatography–thermal desorption mass spectrometry in solving oil-prospecting problems are substantiated.

A simple, rapid, and sensitive method is developed for the simultaneous determination of hydrazine, methylhydrazine, and 1,1-dimethylhydrazine in waters based on precolumn derivatization with benzaldehyde and the determination of the resulting products by reversed-phase HPLC with spectrophotometric detection at 300, 282, and 298 nm, respectively. The effect of imine and micellar catalysis is applied for the first time to obtain hydrazine derivatives on their simultaneous presence. The conditions of derivatization are chosen: the type, pH and concentration of the buffer system; the concentration of the reagent and the surfactant; and the temperature and duration of the reaction. It is found that the derivatization reaction proceeds completely at pH 9.4 in the presence of a catalytic system based on 0.6 M ammonium and 87 mM sodium dodecyl sulfate, and also 3.5 mM reagent at room temperature for 5 min. The quantitative yield of the derivatization products is confirmed by ion chromatography. The limits of detection (S/N = 3) without additional preconcentration are 0.3, 2.3, and 1.3 μg/L, and the linearity range is 1–500, 7–1000, and 5–1000 μg/L for hydrazine, methylhydrazine, and 1,1-dimethylhydrazine, respectively.

INTRODUCTION:Alcohol, tobacco and illicit drug use combined are the largest modifiable health risk factors. Wastewater-based epidemiology (WBE) is a complementary approach for monitoring substance use in the population. In this study we applied WBE technique to a community in the Moscow region to estimate population-level consumption of alcohol, tobacco and morphine. METHODS:Wastewater sampling was carried out over 47 days, in 2018 and 2019, including the New Year period. Analysis of the samples for consumption biomarkers (ethyl sulphate, cotinine and morphine) were undertaken using liquid chromatography tandem mass spectrometry (LC-MS/MS). Daily consumption estimates were then compared with sales/production/prescription data and between different days of the week using Mann-Whitney U test. RESULTS:Alcohol consumption was significantly higher on Sundays and during the New Year and Russian Christmas period compared to weekdays and Saturdays. Tobacco consumption estimates were largely consistent throughout the week. Morphine was detected by WBE during the monitoring period but was inconsistent with prescription record data. DISCUSSION AND CONCLUSIONS:This study provides evidence for the feasibility of conducting WBE in Russia. Estimates of alcohol consumption derived from WBE were higher than average alcohol sales data for the country. The estimated consumption of nicotine is generally consistent with the production data, with estimates higher than in most other countries. Our results also suggest potential illegal use of opioids (morphine-based) in the population. Given the considerable health and economic costs of substance use in Russia, more extensive WBE testing is recommended to inform and evaluate public health policies.

In this work, simple, rapid and highly sensitive method of hazardous chemical 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) determination based on pre-column derivatization with unsubstituted aromatic aldehydes and reversed-phase high performance liquid chromatography-ultraviolet-tandem mass spectrometry (RP HPLC-UV-MS/MS) has been developed. Along with benzaldehyde, commercially available aromatic aldehydes, namely: 2-naphthaldehyde, 2-pyridinecarboxaldehyde, and 2-quinolinecarboxaldehyde, were used as derivatizing reagents in the analysis of hydrazines for the first time. The reactions were studied in a wide pH range by varying reaction time and other conditions. A slightly alkaline pH 9 was shown to be optimal for the derivatization of UDMH by aromatic aldehydes. The quantitative yield of derivatization products under the established conditions was confirmed by HPLC analysis with ampemmetric detection. For all studied reagents, wide linear ranges of concentrations (0.01-1000 mu g/L) in natural water samples were observed. The limits of detection for UDMH in natural water were in the 3.7-130 ng/L range. 2-Quinolinecarboxaldehyde was selected as the most appropriate reagent for HPLC-UV-MS/MS determination of UDMH. In case of using this reagent, the accuracy was in the range of 97-102%, and precision, expressed as RSD was less than 8%. The developed approach does not require laborious stages of pre-concentration and isolation of UDMH from natural water components.

A method for determination of framycetin sulfate in a Framidex preparation (eye and ear drops) by HPLC-UV (λ = 365 nm) using 2, 4-dinitrofluorobenzene as a derivatizing agent has been developed The characteristics of analytical methods determined for the purpose of their validation and relevant criteria for the validity of validated methods with the goal of the quality control of drugs (pharmaceutical substances and drugs) are presented. According to the results of an intralaboratory experiment on the validation assessment of the method by the parameters of the specificity, limit of determination (LOD), linearity, precision and laboratory accuracy, it is shown that the LOD decreases by an order of magnitude, the correlation coefficient is not less than 0.99 correctness (average value — 97.5 – 102.5%; variation coefficient — not more than 2.0%; the confidence range should include 100% of values), convergence (variation coefficient — not more than 1.5%), intermediate precision (variation coefficient — not more than 1.5%). It is shown that the obtained values of metrological characteristics do not exceed the validation criteria and the developed method matches all the well-known requirements of GMP (Good Manufacturing Practice).

The review surveys the works of staff members, students, and graduate students of the Divison of Analytical Chemistry, Department of Chemistry, Lomonosov Moscow State University on the use of microemulsions in liquid and electrokinetic chromatography. Microemulsions are used as promising extractants for the extraction of hydrophobic target substances from food, pharmaceutical, environmental, etc., samples. The possibility of the subsequent separation of microemulsions and the preconcentration of components to be determined in an organic phase was demonstrated. The approaches proposed are characterized by low detection limits; they considerably simplify a sample preparation process to shorten the total analysis time and to decrease the total number of stages, which decreases the error of determination.

A method for determination of framycetin sulfate in a Framidex preparation (eye and ear drops) by HPLC-UV (λ = 365 nm) using 2, 4-dinitrofluorobenzene as a derivatizing agent has been developed The characteristics of analytical methods determined for the purpose of their validation and relevant criteria for the validity of validated methods with the goal of the quality control of drugs (pharmaceutical substances and drugs) are presented. According to the results of an intralaboratory experiment on the validation assessment of the method by the parameters of the specificity, limit of determination (LOD), linearity, precision and laboratory accuracy, it is shown that the LOD decreases by an order of magnitude, the correlation coefficient is not less than 0.99 correctness (average value — 97.5 – 102.5%; variation coefficient — not more than 2.0%; the confidence range should include 100% of values), convergence (variation coefficient — not more than 1.5%), intermediate precision (variation coefficient — not more than 1.5%). It is shown that the obtained values of metrological characteristics do not exceed the validation criteria and the developed method matches all the well-known requirements of GMP (Good Manufacturing Practice).

The possibility of improving the HPLC-UV determination of 1, 1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) with preliminary derivatization with 2-nitrobenzaldehyde (2NBA) and 4-nitrobenzaldehyde (4NBA) in an aqueous medium when using micellar catalysis of the reaction to obtain the derivatives is studied. Conditions of UDMH derivatization (pH, concentrations of the reagent and surfactant (SAS), temperature and reaction time) were optimized. It is shown that complete derivatization occurs at room temperature during 45 and 30 min (for 2NBA and 4NBA, respectively) at pH 9 in the presence of 87 mM sodium dodecyl sulfate (SDS) and the excess content of the reagents. Ion chromatography was used to prove the quantitative yields under conditions of derivatization by the absence of UDMH in the reaction mixture. Micellar catalysis provides the completeness of derivatization carried out under milder conditions and in the region of low UDMH concentrations thus expanding the linear range of UDMH determination in water. ZORBAX Eclipse Plus C18 column (150 × 3.0 mm, 3.5 μ m) was used for separation of the components. A mixture of acetonitrile and 10 mM ammonia buffer solution pH 7 (50/50 vol.%) at a flow rate of 0.7 ml/min in isocratic mode was used as a mobile phase. Detection of dimethylhydrazines (2NBA and 4NBA) was performed at 308 and 394 nm, respectively. The obtained detection limits of UDMH ( S / N = 3) were 3 and 1.5 μ g/L for 2NBA and 4NBA, respectively. Duration of chromatographic analysis was 15 min. The developed technique of water analysis provides simple, sensitive and reproducible HPLC-UV determination of UDMH in a concentration range of 5 – 1000 μ g/L without additional preconcentration.

Non-ionic surfactants are permanent components of wastewater of various origins, and their removal is necessary for sewage treatment. A new method of electrochemical treatment of wastewater for non-ionic surfactant destruction has been proposed. Effective destruction of both alkoxylated and phenoxylated non-ionic surfactants was performed using β-Pb1–xBixO2–0.5x anodes prepared by electrodeposition. The method proposed is based on the generation of active oxygen-containing species (e.g., OH•, HO2•) at the anode followed by chemical interaction between these radicals and organic molecules, which results in the destruction of pollutants. Oxide materials obtained by electrodeposition contained ~ 4.5 % of bismuth and have the β–PbO2 lattice. The insertion of bismuth into the composition of lead dioxide prepared by electrodeposition resulted in an increase in their specific surface area from 0.66 to 2.5 m2 g−1. Modification of β–PbO2 by bismuth led to the shift of oxygen evolution potentials toward more positive values. Effective electrooxidation of non-ionic surfactants was achieved in the solutions exposed to electrochemical treatment. There were no accumulations of metabolites in the solutions during electrolysis. Chemical oxygen demand decreased from 80 to 5 mg O2 dm−3, and total organic carbon (TOC) decreased from 24 to 1.5 ppm during 1 h of the electrochemical treatment. The electrode material was stable under electrolysis conditions. No accumulation of both lead and bismuth species in the solution under electrochemical treatment was found.