[Determination of 2,4-dimethylhydroxybenzene by chromatographic methods in forensic toxicological research of biological material]. / Opredelenie 2,4-dimetilgidroksibenzola khromatograficheskimi metodami pri khimiko-toksikologicheskom issledovanii biologicheskogo materiala.

OBJECTIVE: Is to develop a method for determining 2.4-dimethylhydroxybenzene (2.4-DMHOB) in biological material. The analytical methods used in the experiments were extraction, column chromatography of normal pressure, TLC, GC-MS and HPLC. To extract the analyte from the bioactive matrix, maceration with the binary insulating agent acetone-ethyl acetate (3:7) was used, observing the 2:1 mass ratio of the «insulating agent-matrix¼. Optimal conditions of semi-preparative analyte chromatography were achieved in column (150×10 mm) of «Silasbor¼ S-18 sorbent in elution with a mixture of acetonitrile-water (7:3), which was used in the proposed cleaning scheme, combining extraction and reversed-phase column chromatography. The application of the mobile phase of tetrachloromethane-dioxane (9.5:0.5) has been substantiated for the selective determination of 2.4-DMHOB by TLC («Sorbfil¼ plates). The expediency of confirming identification of the analyte in the form of 2.4-dimethyltrymethylsilylphenol using GC-MS (DB-5MS EVIDEX column (25.000×0.2 mm), stationary phase (5%-phenyl)-methylpolysiloxane, carrier gas - helium) has been shown. The group of characteristic particles in the mass spectrum of trimethylsilyl analyte derivative was represented by 45; 59; 73; 82; 91; 105; 119; 135; 149; 163; 179; 194 m/z ions. HPLC (Discovery C18 250×4.6 mm column, eluting liquid - acetate buffer solution with pH 5.5 - acetonitrile, 50:50) was used to confirm the identification and quantification of 2.4-DMHOB. A method for determining 2.4-DMHOB by the HPLC method in biological material (liver tissue) is proposed, which corresponds to the criteria of linearity, selectivity, accuracy, precision and stability. The minimum detectable quantity of 2.4-DMHOB in the bioactive matrix is 0.5 µg/g, the minimum determined quantity is 1.2 ug/g.

A novel impedimetric sensor based on N-acetyl-L-cysteine for the determination of hydroxyl radicals in cell cultures in vitro.

We report a novel impedimetric sensor based on a graphite electrode impregnated with polyethylene and paraffin under vacuum (IGE) modified with electrochemically deposited gold and a self-assembled monolayer of N-acetyl-L-cysteine (NAC/Au/IGE) for selective and sensitive determination of extracellular hydroxyl radicals (OH•) generated by living cells. The application of a sulphur-containing molecule oxidized by OH• predicts the high selectivity of the sensor, and the utilization of the non-faradaic impedance spectroscopy for recording an analytical response makes it possible to achieve superior sensitivity with a detection limit of 0.01 nM and a linear dynamic range of 0.08-8 nM. Meanwhile, NAC/Au/IGE demonstrated a strong potential of detecting OH• generated by biological objects via successful determination of extracellular hydroxyl radicals generated by normal fibroblast cells and prostate carcinoma cells.

[Study of 2,6-di(propan-2-yl)phenol stability in biomaterial]. / Izuchenie ustoichivosti 2,6-di(propan-2-il)fenola v biologicheskom materiale.

The aim of this study is to research the stability of 2.6-di(propan-2-yl)phenol in biomaterial. GC-MS (column DB-5MS EVIDEX (25 m×0.2 mm); stationary liquid phase of 5%-phenyl-95% dimethylpolysiloxane), TLC (Sorbfil plates, mobile phase of hexane-diethyl ether (9:1) and spectrophotometry (solvent medium - 95% ethanol) were used as methods of analysis. 2.6-di(propan-2-yl)phenol was isolated from the biomatrix (liver tissue) by infusion with a mixture of ethyl acetate-acetone (7:3). The analyte was purified by combining extraction (water-ethyl acetate system) and semi-preparative chromatography on a column of silica gel L 40/100 µm, eluent - hexane-acetone (7:3). It was found that at -22 °C, 0 °C, 12 °C, 20 °C and 30 °C 2.6-di(propan-2-yl)phenol can be present in the liver tissue for 119, 98, 70, 56 and 42 days, respectively. The possibility of mathematical description of analyte decomposition dynamics in biomaterial (liver tissue) at the considered temperatures on the basis of hyperbola equation has been studied. The experimentally calculated coefficients in the hyperbola equation (km) for temperatures -22 °C, 0 °C, 12 °C, 20 °C and 30 °C are equal to 1823, 1130, 697, 510, and 255, respectively. The dependence km on the conserving temperature (tо) was educed. The equation for the description of dependence is offered: km=30.61∙(50-to)-402.39. It is shown that this equation can be the basis for prediction of 2.6-di(propan-2-yl)phenol stability in biomaterial (liver tissue) in the temperature range from -22 °C to 30 °C.

[Propofol: use, toxicology and assay features]. / Propofol: primenenie, toksikologicheskaya kharakteristika i osobennosti opredeleniya.

The study objective is to review the literature on the use, pharmacological properties, toxicology, and assay methods for intravenous anesthetic propofol. The scope and forms of propofol use, its pharmacokinetics, biotransformation features, which occurs more than 90% in the liver, and side effects associated with propofol use for anesthesia, are addressed. Propofol infusion syndrome (also known as PrIS) and deaths from propofol overdose due to medical errors, abuse, suicide attempts, and homicide are reported. Propofol identification and assay methods based on high-performance liquid chromatography (HPLC), gas chromatography with mass spectrometry (GC-MS), and liquid chromatography (LC) are described. The features of the methods performance are outlined; biological materials (the study objects) are listed: mainly blood and plasma, as well as urine, bile, hair, etc. The relevance of a comprehensive forensic chemical study of propofol is indicated, though there are few forensic studies of propofol.

[Study of the stability of 2-methoxy-4-(2-propenyl) hydroxybenzene in biological material]. / Izuchenie ustoichivosti 2-metoksi-4-(2-propenil) gidroksibenzola v biologicheskom materiale.

The purpose of this work is to study the stability of 2-methoxy-4-(2-propenyl)hydroxybenzene [2-MO-4-(2-P)HOB] in biological material. For analysis, gas chromatography-mass spectrometry (GC-MS) was used: column DB-5MS EVIDEX (25 m × 0.2 mm) with a stationary phase of 5%-phenyl-95%-dimethylpolysiloxane; thin layer chromatography (TLC): Sorbfil plates, hexane-dioxane-propanol-2 mobile phase (40:5:1) and UV spectrophotometry (solvent - 95% ethanol). 2-MO-4-(2-P)HOB was isolated from the biomatrix (liver tissue) by infusion with a mixture of ethyl acetate-acetone (7:3). Purification of the analyte was carried out by combining extraction (water-ethyl acetate system) and semi-preparative column chromatography [sorbent - silica gel L 40/100 µm, eluent - hexane-dioxane (8.5:1.5)]. It was established that at -22 °C, 4 °C, 12 °C, 20 °C and 30 °C 2-MO-4-(2-P)HOB is stored in the liver tissue for 385, 357, 301, 245 and 217 days, respectively. We studied the possibility of mathematical description of the dynamics of analyte decomposition in a biomaterial (liver tissue) at the indicated temperatures using the hyperbolic equation. The coefficients in the hyperbola equation (kav), calculated according to the results of the experiment, for temperatures of -22 °C, 4 °C, 12 °C, 20 °C and 30 °C amounted to 6223, 3036, 2387, 1903 and 932, respectively., which is described by the equation: kav=101.19∙(50-to)-1272.78. It was established that on the basis of this equation it is possible to predict the nature of the stability of 2-MO-4-(2-P)HOB in the biomaterial (liver tissue) at temperatures in the range from -22 °C to 30 °C.

[Features of assay and decomposition dynamics of 2-methoxy-4-(1-propenyl)hydroxybenzene in biological material]. / Osobennosti opredeleniya i dinamiki razlozheniya 2-metoksi-4-(1-propenil)gidroksibenzola v biologicheskom materiale.

The objective was to study the features of assay and dynamics of decomposition of 2-methoxy-4-(1-propenyl)hydroxybenzene in biological material. Extraction, semi-preparation chromatography, TLC, HPLC, GC-MS and UV-spectrophotometry were used as test methods. 2-Methoxy-4-(1-propenyl)hydroxybenzene was extracted from the biological material by double infusion (45 min each) with ethyl acetate at a 2:1 mass ratio of isolating agent and biomatrix. Purification was performed by extraction and chromatography in a semi-preparative (190×10 mm) L 40/100 µm silica gel column using a hexane-dioxane (7:3) eluent. The analyte was determined by TLC methods (Sorbfil plates, hexane-acetone 9:1 as a mobile phase), HPLC [Discovery C18 HPLC Column (250×4.6 mm), acetonitrile-acetate buffer pH 5.5 (5:5) as a mobile phase], GC-MS [DB-5MS EVIDEX (25 m×0.2 mm) column with 5%-phenyl-95% dimethyl polysiloxane as a stationary phase], UV-spectrophotometry (95% ethanol as a solvent). The proposed assay method for 2-methoxy-4-(1-propenyl)hydroxybenzene in biomaterial (liver tissue) is validated for linearity, selectivity, accuracy and precision. The study results showed that the decomposition rate of the analyte increases as the store temperature increases. At 0-2 °C, 8-10 °C and 18-22 °C 2-methoxy-4-(1-propenyl)hydroxybenzene is stable for 480, 390 and 260 days respectively.

[Development of methods for determining and studying the persistence of 2,4-dimethylhydroxybenzene and 2,6-dimethylhydroxybenzene in biological material]. / Razrabotka metodik opredeleniya i izuchenie sokhranyaemosti 2,4-dimetilgidroksibenzola i 2,6-dimetilgidroksibenzola v biologicheskom materiale.

OBJECTIVE: To study the features of the determination and preservation of 2.4-dimethylhydroxybenzene and 2.6-dimethylhydroxybenzene in biological material. Extraction, semi-preparative chromatography, TLC, GC-MS and UV spectrophotometry are considered as methods of analysis. The 2.4- and 2.6-dimethylhydroxybenzenes were isolated from the biomaterial by double infusion (30 minutes each) with a mixture of ethyl acetate-acetone (7: 3) at a weight ratio of the insulating liquid and biomaterial of 2:1. Purification was carried out by extraction and chromatography in a semi-preparative (190×10 mm) column of silica gel L 40/100 µm using the eluent hexane-dioxane-propanol-2 (80: 5: 1). Analytes were determined by TLC (Sorbfil plates, mobile phase hexane-dioxane-propanol-2 (120: 5: 1)), GC-MS (DB-5MS EVIDEX column (25 m × 0.2 mm) with a stationary phase (5%-phenyl) - methylpolysiloxane), UV spectrophotometry (solvent - 95% ethanol). The developed methods for the determination of 2.4- and 2.6-dimethyl derivatives of hydroxybenzene in biomaterial (liver tissue) are validated according to the criteria of linearity, selectivity, correctness and precision. The study of the dynamics of decomposition of 2.4- and 2.6-dimethyl hydroxybenzene derivatives in model mixtures with liver tissue, carried out using the developed techniques showed that with an increase in temperature the duration of preservation of analytes in biological material decreases. Moreover, the 2.4-isomer is more stable during storage than the 2.6-isomer. At temperatures of -25 °C, 0-2 °C, 8-10 °C, 20-22 °C, 36 °C the duration of retention of 2.4-dimethylhydroxybenzene is 402, 379, 358 and 224 days, respectively, the duration of retention of 2.6-dimethylhydroxybenzene is 356, 312, 224 and 136 days, respectively.

[Features of determination of 2-methoxyhydroxybenzene in the study of biological material]. / Osobennosti opredeleniya 2-metoksigidroksibenzola pri issledovanii biologicheskogo materiala.

The aim of the study was to develop a method for the determination of 2-methoxyhydroxybenzene in biological material. TLC, UV spectrophotometry, HPLC and GC-MS were used in the experiments. The use of a mixture of ethyl acetate-acetone (7:3 by volume) for the isolation of 2-methoxyhydroxybenzene from biological material is justified. Optimal isolation conditions are established. Purification of the substance was carried out by extraction and chromatography in sorbent column (KCC-3) 80/120 µm. For preliminary identification, TLC was used on Sorbfil PTSX-AF-A-UV plates. Confirmation of identification was carried out by the UV spectrum in ethanol by HPLC with the retention time in a 250×4.6 mm column «SunFire C18¼ (mobile phase acetonitrile-0.025 M potassium dihydrogen phosphate solution 6: 4). Confirmation identification and quantification was performed by GC-MS using a fixed phase capillary column of 5% phenyl-95% methyl polysiloxane after derivatization of the analyte with N-trimethylsilyl-N-methyl trifluoroacetamide (heating for 30 min at a temperature of 60 °C). Ions 45, 58, 73, 91, 107, 136, 151, 166, 181, 196 m/z are present in the mass spectrum of the derivative. The validation of the methodology for the determination of 2-methoxyhydroxybenzene in biomaterial based on the application of the GC-MS method was carried out. The compliance of the methodology with the criteria of linearity, selectivity, correctness, precision and stability is established. The detection limit and the limit of quantification are 8 and 15 µg per 100 g of biomaterial, respectively.