Journal of Analytical Chemistry最新文献

A new simple, precise, and sensitive charge transfer method for estimation of tioconazole drug in pure form and Gyno-Trosyd tablet was developed based on the reaction of the n-electron donor tioconazole drug with π-receptors, namely chloroanilic acid, 2,3-dichloro-5,6-dicyano-1,4-benzoquinon, and picric acid. The complexes were determined spectrophotometrically at 460, 402, and 520 nm for the tioconazole-2,3-dichloro-5,6-dicyano-1,4-benzoquinon, tioconazole-picric acid, and tioconazole-chloroanilic acid complexes, respectively. The conditions under which experiments should be conducted have been extensively studied. Beer’s law was obeyed over the working concentration ranges of 10–100, 10–250, and 2–140 μg/mL for tioconazole-2,3-dichloro-5,6-dicyano-1,4-benzoquinon, tioconazole-chloroanilic acid, and tioconazole-picric acid complexes, respectively.

A review of the literature and regulatory documents on the identification and determination of organic compounds that form the component composition and consumer properties of wines is presented. It is noted that the capabilities, information content, and versatility of modern chromatographic methods in combination with mathematical software have significantly increased the degree of automation and reliability of obtaining data on the identification and determination of a wide range of components in wine. Conditions for the determination of high and low concentrations of organic compounds responsible for the qualitative and regional characteristics of wines in the component composition are discussed. Various gas chromatography and gas chromatography–mass spectrometry methods providing the reliable determination of relatively volatile components are most widely used to solve the problems of identification and determination of components responsible for the advantages and disadvantages of wine products. Nonvolatile components of wines are determined by high-performance liquid chromatography with various detection methods and by high-performance capillary electrophoresis. The main approaches to establishing the profile and regional identity of wines in terms of component composition, which combine the capabilities of modern analytical methods with statistical analysis methods (multiple regression analysis, general linear models, multidimensional scaling, covariance and canonical analysis, classification and machine learning methods, and neural networks) are analyzed. Examples of their use in actual practice are demonstrated.

A sorbent with magnetic properties, functionalized with humates, in combination with gas chromatography–mass spectrometry is proposed for the determination of phenolic xenoestrogens (ED) in bottom sediments. The octylphenol (OP), nonylphenol (NP), and bisphenol A (BPA) ED are chosen as test samples. Along with ED, the distribution of the naturally occurring estrogen, 17β-estradiol (ES), is studied. Sorption preconcentration is carried out under dynamic conditions: a sorbent weighing 0.5 g is placed in a borosilicate glass column, on both sides of which magnets are placed to immobilize the sorbent. The analytical characteristics of the determination method are established using model samples of bottom sediments selected in a background area with a minimal anthropogenic impact. The limit of quantification for ED is 30–60 ng/kg (dry weight). In analyzing real samples, the sensitivity of the method is reduced by 3–4 times due to matrix effects of the presence of petroleum products in waters. The ED content of bottom sediments at the site of wastewater discharge into the river Don near the city of Voronezh, as well as on the Black Sea coast of the Caucasus (area of the city of Tuapse and the village of Olginka) was monitored. The maximum concentrations of OP, NP, BPA, and ES in bottom sediments were found in the area of the port of Tuapse, where they were 5.7, 8.1, 6.2 and 0.9 µg/kg, respectively.

The test samples are polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), highly toxic and widely prevalent organic pollutants in natural waters. The feasibility of using dispersive liquid–liquid microextraction (DLLME) for extracting PCBs and PAHs, followed by their determination by GC–MS, was assessed in the presence of both contaminants. A DLLME method employing a binary dispersing agent was proposed, ensuring the simultaneous extraction of analytes with efficiency ranging from 80 to 97%. The proposed procedure enabled the GC–MS determination of 16 PAHs and 7 PCBs in natural waters in a wide concentration range of 2.0 × 10^–5–0.04 µg/mL with an average error of 7–18% for PAHs and 11–18% for PCBs. The relative standard deviations for repeatability and reproducibility were found to be 3.1–6.5 and 4.3–7.7%, respectively, for PAHs, and 2.8–5.3 and 3.4–6.0%, respectively, for PCBs.

This work presents a novel on-line flow-batch dispersive liquid-liquid microextraction system for the determination of molybdenum in water, meat, and vegetable material with electrothermal atomic absorption spectroscopy (ET AAS) as detection technique. After optimizing the experimental conditions, the analytical performance of the new methodology was determined. A limit of detection of 0.03 µg/L for water and 0.02 µg/kg for the other matrices, as well as an enrichment factor of 130 were obtained employing this methodology. Standard reference materials were used for accuracy and precision evaluation. No significant differences were found at the 95% confidence level between the certified and obtained values, and precision expressed as repeatability (RSD) was better than 5% in all cases. The developed automated methodology offers great advantages when compared to manual dispersive liquid-liquid microextraction, such as low risk of contamination while working in closed systems, minimal handling, reduced exposure of the analyst to the chemical products, greater security, improvement in repeatability and the elimination of the laborious and time-consuming procedure of phase separation by centrifugation. The method was successfully applied for the determination of molybdenum in natural groundwater, bovine and sheep meat, and pasture samples.

A possibility of studying effects of the main background ions formed by the main elements of inductively coupled plasma (H, N, O, and Ar) at the working parameters of the normal (“hot”) plasma mode by thermodynamic modeling is assessed. Such ions, responsible for the strongest spectral interferences in the mass spectra are always observed upon the injection of aqueous (“wet”) sample solutions into inductively coupled plasma mass spectrometers (ICP MS). The quantitative composition of the main background ions in an ICP MS is calculated as a function of plasma temperature in the temperature range from 3000 to 8000 K using thermodynamic modeling. The results of modeling were compared with the experimental data on the measured mass spectra of the main background ions and a high degree of correlation between the theoretical and experimental results was shown. The agreement between the results of calculations the experimental data validates the thermodynamic model of thermochemical processes in an ICP MS used and its applicability to subsequent calculations in fulfilling analytical tasks. A possibility of the unambiguous assessment of gas-kinetic plasma temperature is confirmed by comparing the theoretical and experimental mass spectra of the main ICP background ions in a normal mode. It was found that the calculated and experimental data on the concentration of only NO⁺ ions do not agree with the regularities noticed for the other background ions in the normal ICP mode.

Inorganic zeolites, or microporous crystalline aluminosilicates, possess high porosity, well-developed specific surface area, uniform pores, and ion-exchange properties, which determine their molecular sieve and adsorption properties. The use of zeolites as catalysts, desiccants for solvents and gases, and selective adsorbents for the separation of low-molecular-weight compounds is widely known. Zeolites also serve extensively as packing materials for chromatographic columns in gas-adsorption chromatography. However, their application to high-performance liquid chromatography (HPLC) is less recognized. In HPLC, the retention of adsorbates depends not only on adsorption interactions but also on the molecular sieve effect in the micropores and kinetically selective effects. Additional interactions with the mobile phase components alter the thermodynamic parameters of the adsorbates interaction with the zeolite, decrease effective pore size, and hinder the diffusion of the separated compounds into the adsorbent’s pores. Despite these challenges, zeolites remain promising adsorbents due to their strictly determined pore size (d_pore) and geometry, as well as their customizable polarities, which ensure high selectivity for the separation of low-molecular-weight compounds. The most promising zeolites for HPLC are wide-pore zeolites (d_pore 0.6–0.8 nm) with 8, 10, 12, and 14-member ring channels. This review offers a concise overview of the classification, composition, and structure of zeolites and their impact on the adsorption properties of these adsorbents. Data on the use of zeolites in HPLC are also systematized.

A micellar microextraction technique has been developed for the preconcentration and spectrophotometric determination of phosphate ions in aqueous media. This method is based on the formation of a reduced form of molybdophosphoric heteropolyacid and its extraction from the aqueous phase into a supramolecular solvent. The supramolecular solvent phase is formed in situ by introducing an amphiphile and a coacervation agent into the acidic aqueous phase. The feasibility of using biodegradable alkyl polyglucoside (C₈–C₁₀) as an amphiphile and carboxylic acids as coacervation agents has been investigated. In the acidic medium required for the formation of the reduced form of molybdophosphoric heteropolyacid, the phase of the supramolecular solvent is separated. The maximum absorbance of the extract is achieved using pivalic acid as the coacervation agent. The procedure is characterized by the limit of detection (3σ) for phosphate ions 5 µg/L. The technique is environmentally friendly and does not require the use of expensive equipment.

A technology is developed for manufacturing planar microfluidic chips (MFCs) based on Silgard 8040, encompassing template fabrication, mold production, sealing, and adsorbent filling. These MFCs, filled with a Porapak-Q adsorbent, facilitate sample preparation and calibration under uniform conditions, integrating both sample collection and preconcentration stages. Experimental investigations have identified optimal conditions for acetone preconcentration using Silgard 8040-based MFCs, achieving a maximum concentration factor of 43 at adsorption temperature (T_ads) of 0°C, desorption temperature (T_des) of 70°C, adsorption volume (V_ads) of 45 mL, and desorption time (t_des) of 1 s. The feasibility of using MFCs for sample collection and preparation, taking into account sample storage time, has been evaluated. The procedure maintains accuracy within 6–10% over 8 h without a necessity for additional drying of the collected samples from exhaled air.

An original bench-scale installation based on the principles of online magnetic solid-phase extraction is developed. The setup includes a borosilicate glass column packed with Fe₃O₄@MIP-BPA, which is fixed with two neodymium magnets. Compared to using one magnet, a design with two magnets ensures the uniform distribution of the sorbent over the entire cross-section of the column. The highest concentration factors (EF = 3216) and the degree of desorption of bisphenol A (BPA) are achieved, respectively, at a volumetric solution flow rate (W) of 2.0 mL/min and with eluting BPA with methanol (W = 0.4 mL/min). The determination of BPA in concentrates from model media by GC−MS provides high sensitivity of the developed method for determining BPA. In analyzing model solutions prepared in distilled water, the limit of detection (LOD) is 0.3 ng/L. In analyzing river water, the LOD increases by approximately 2 times. In analyzing soils, LOD = 2.2 ng/kg dry weight. Soils, compared to water bodies, contain a larger number of interfering components; the sensitivity of the method is reduced by 7–8 times. Bottom sediments are even more contaminated; the LOD more than doubles compared to the determination of BPA in soils.