Application of carbon monolith based on exfoliated graphite for sorption and subsequent chromatographic determination of volatile organic compounds in soil air

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.

Headspace gas chromatographic determination of β-caryophyllene in Epilobium angustifolium L. extracts

Epilobium angustifolium L. is a plant widely used in folk medicine. It is rich in biologically active compounds including phenols, flavonoids, terpenes, aliphatic acids and sterols; however, until now, little attention has been paid to its volatile components. This research demonstrated that Epilobium angustifolium L. is rich in β-caryophyllene that is possibly responsible for its unique therapeutic properties. The leaves of Epilobium angustifolium L. are traditionally used as a tea. On the other hand, β-caryophyllene is soluble in oils, thus an extract of Epilobium angustifolium L. in edible oils should also demonstrate a healing effect. Therefore, quick and reliable methods of β-caryophyllene determination in edible oils and in water solutions are required. In this work, headspace gas chromatography is suggested to determine β-caryophyllene. At the optimized chromatographic conditions for β-caryophyllene solutions in coconut oil the calibration curve was linear up to 10 mg g–1, the detection limit was 60 µg kg–1, for β-caryophyllene solutions in water the calibration curve was linear up to 40 µg l–1, and the detection limit was 6 µg l–1. The methods were applied for the β-caryophyllene determination in the extract of Epilobium angustifolium L. in sunflower oil and in Epilobium angustifolium L. tea.

Simple extraction procedure for free amino acids determination in selected gluten-free flour samples

The simple extraction of flours samples followed by free amino acids determination procedures was studied and optimised. The conditions of amino acids derivatisation reaction with ninhydrin for chromatographic determination of free amino acids sum was discussed. The developed method was processed in terms of linearity, precision, accuracy, and limits of detection and quantification. Moreover, capillary isotachophoresis and HPLC methods were applied for individual free amino acids determination. The proposed extraction procedure is simple, fast and convenient for different flours samples. Studied procedures were used for free amino acids determination in twelve gluten-free flour samples (corn, oat, soy, rice, pumpkin, millet, peanut, hemp seed, buckwheat, amaranth, pea and chickpea) and the obtained results were compared with wheat flour.

Spectrophotometric and High Performance Liquid Chromatographic Determination of Carbamazepine in Tablets Dosage Form

Today, millions of people suffer from epilepsy, one of the most common chronic neurological diseases worldwide. Carbamazepine is a first-line drug used in the treatment of epilepsy. High performance liquid chromatographic and spectrophotometric methods have been developed for the determination of carbamazepine in tablet dosage forms. UV spectrums were recorded in the wavelength range of 200-800 nm using methanol solvent, and the wavelength for determining carbamazepine was selected as 286 nm. LC analysis was performed using Agilent Extend-C18 column and mobile phase composed of KH2PO4 solution(pH: 3.5) and acetonitrile (40:60 v/v) at a flow rate of 1.2 mlmin-1. These analytical methods were validated in agreement with the International Conference on Harmonization (ICH) guidelines using the following analytical parameters: specificity, linearity, precision, accuracy, detection and quantification limits, and robustnes. Analytical methods showed wonderful linearity (r2>0.999) in the concentration range of 5-25 μg mL-1 for boths methods. Precision (R.S.D%<1.17) and recevery for both methods was in the range of 99-101%, which shows accuracy of these methods. These proposed methods were found to be accurate, reliable, fast, simple, The F-test and t-test were used to perform statistical comparison of these methods, and the results of both analytical methods indicated no significant difference. As a result, the proposed methods can be used to analyze carbamazepine in pharmaceutical formulations.

Chromatographic determination of organohalogen compounds in swimming pool water

The purpose of the work was to search for a sorbent with good selective properties for water purification. For this purpose, we determined the organohalogen compounds in the water of a swimming pool. A method of gas-liquid chromatography was used, using packed and capillary chromatographic columns. To concentrate the impurities of the organohalogen compounds, an automatic vapour-phase dispenser was used. This established that the swimming pool water, taken in the evening, had a complex composition of components, including 33 organohalogens, which have different toxicities for the human body. These are classed as belonging to the first and second groups of hazards. Identification of the individual component composition was carried out by determining the relative retention times of the test compounds and standard samples of the organohalogen compounds dissolved in methanol. Out of the entire range of the organohalogen compounds contained in the swimming pool water it was determined that the highest concentration of chloroform was 0.024 mg/dm3 and the highest concentration of carbon tetrachloride was 0.018 mg/dm3. The total content of organohalogen substances in the swimming pool water was 0.370 mg/dm3, which increases the risk of human diseases while the swimming pool is in operation. It is proposed to clean the water in the swimming pools from toxic impurities by an adsorption method using rocks containing zeolite from the Tatar-Shatrashan deposit, which are characterized by a sufficiently high sorption capacity in relation to the organohalogen compounds.

Extraction sample preparation for chromatographic determination of residual quantities of acidic penicillins in milk

The distribution of six acid-type penicillins (penicillin G, penicillin V, oxacillin, cloxacillin, nafcillin, dicloxacillin) in the extraction systems of chloroform–aqueous solutions of ammonium sulfate was studied. The reported distribution coefficients values of penicillins demonstrated the effectiveness of using ammonium sulfate as a salting-out agent. Based on the data obtained, a procedure for milk sample preparation was developed for the quantification of the residual content of six acid-type penicillins.

Extraction-chromatographic determination of narcotic drugs and psychotropic substances in objects of complex matrix composition

A comparison of the capabilities of two methods for extraction-chromatographic determination of narcotic drugs and psychotropic substances in various objects (syrups, ointments, tablets, herbal mixtures, etc.), the screening methanol method commonly used in the practice of customs and forensic examination and the proposed extraction method based on the use of water phase (in particular, water solutions of salts) for preliminary effective separation of analytes from matrix components was made. In extraction systems of hexane–water, hexane–aqueous solutions of inorganic salts (sodium chloride, dipotassium phosphate and potassium carbonate), chloroform–water, the method of gas chromatography – mass spectrometry was used to determine the distribution constants (P) of organic bases – narcotic drugs and psychotropic substances (N-methylephedrine, methamphetamine, amphetamine, methadone, dihydrocodeine, hydrocodone, oxycodone, ketamine, cocaine zolpidem, fentanyl, harmine, harmaline). Based on the obtained extraction characteristics of analytes and matrix components, the optimal extractants and extraction conditions, which ensure the maximum efficiency of separation of analytes and matrix components, as well as the concentration of the analyte were substantiated. The use of extraction using water and aqueous solutions of salts provides both a sharp decrease in the detection limit (from 10–3 to 10–7 mol/dm3) in comparison with the methanol method and stable working of chromatographic equipment due to the removal of thermally unstable matrix components was shown.