Journal of Analytical Chemistry最新文献

A simple, rapid, and sensitive procedure is developed for the determination of hydroxylated polycyclic aromatic hydrocarbons (2-hydroxynaphthalene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 3-hydroxyphenanthrene, 2-hydroxyphenanthrene, 1-hydroxypyrene, and 6-hydroxychrysene) in urine by gas chromatography–mass spectrometry. Sample preparation is based on dispersive liquid–liquid microextraction with trichloromethane in an acidic medium. Derivatization is carried out in a heated injector port using the reagent N,O-bistrimethylsilyltrifluoroacetamide. The type of dispersing solvent is experimentally selected and the optimal ratio of the following factors, i.e., pH value, volume of dispersing solvent, and extraction time, is found using a three-factor experiment. A high-temperature capillary column NT-8 is used in a temperature gradient mode for analysis by gas chromatography–mass spectrometry. The linearity range of the calibration function is found to be 0.5–100 ng/mL. The developed procedure for determining hydroxylated PAH in urine is tested on urine samples from aluminum production workers.

A facile kinetic spectroscopic technique was devised and validated for the precise estimation of memantine hydrochloride. This method depends upon the measurement of various kinetic characteristics of the reaction between the drug and 1-chloro-2,4-dinitrobenzene in an alkaline medium at 70°C. The resultant memantine-dinitrobenzene complex exhibits a distinctive absorbance maximum at 290.5 nm. Spectroscopic analysis was conducted by scanning the complex within the 200 to 800 nm range using a Shimadzu UV-1900 spectrophotometer. Experimental conditions, including reagent concentration, base quantity, order of addition, and reaction temperature, were optimized. The reaction mechanism and stoichiometric ratio of the drug with the reagent were elucidated. Employing various kinetic methodologies such as initial rate, fixed time, and fixed absorbance under optimal conditions enabled the construction of calibration curves and accurate estimation of memantine hydrochloride. The method demonstrated linearity within the concentration range of 3.0 to 7.0 μg/mL. Precision assessment yielded satisfactory relative standard deviations of 2.05 for intra-day and 1.96 for inter-day precision studies. Accuracy studies revealed mean recoveries ranging between 98.55–102.34%. Moreover, the proposed method effectively determined memantine hydrochloride in a commercial formulation.

The adsorption of toxic ions Be(II), Bi(III), Cd(II), Cr(III), and Pb(II), and also noble metals Ag(I), Au(III), and Pd(II), from aqueous solutions is studied using carbon nanotubes (CNTs), a magnetic nanosorbent composed of CNTs and magnetic nanoparticles (CNT@MNP), and activated carbon (AC). An advantage of CNT-based adsorbents over AC in terms of capacity was demonstrated, with an increase of approximately 1.5–2 times. The adsorption capacity of the synthesized magnetic adsorbent depends on the morphology of CNTs grown on iron subgroup catalysts: nickel (CNT(Ni)), cobalt (CNT(Co)), and iron (CNT(Fe)). CNT@MNP exhibited superior performance over other carbon adsorbents in magnetic solid-phase extraction, effectively separating solid and liquid phases. Additionally, composite adsorbents containing CNT(Co) and CNT(Fe) were noted for their cost-effectiveness, as they yielded satisfactory results, surpassed those obtained with the individual CNT-based adsorbents. Procedures were developed using these carbon adsorbents and their performance in the determination of elements in aqueous solutions by arc atomic emission spectrometry was estimated.

A brief overview of chromatographic methods for determining free bisphenol A (BPA) in technical and food products is presented. Bisphenol A is used as a monomer in the production of some plastics and epoxy resins. The concentration of free BPA may exceed the permissible level in food plastic containers and in food products packaged in these containers. The maximum permissible concentration of BPA in water, in water bodies of domestic and drinking water and in cultural and household water use is 0.1 mg/dm³. In European countries, the migration value of BPA for plastics in contact with food products is 0.6 mg/kg. Gas chromatography with preliminary derivatization by the silylation or acylation of the analyte is most often used to determine BPA in plastics, food products, and biological fluids. Direct determination methods have been developed using gas-liquid chromatography on heat-resistant columns. Flame ionization, fluorometric, and mass-selective detectors are used as detection devices. HPLC with optical and mass-selective detectors is used to determine BPA. Thin-layer chromatography has also been used for determining BPA. Solid-phase extraction, liquid−liquid extraction, dispersive liquid−liquid microextraction, and a combined extraction method with separation in acetonitrile (QuEChERS) are used in BPA sample preparation.

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.