Journal of Analytical Chemistry最新文献

A straightforward procedure is developed for the selective determination of alpha-tocopherol acetate (vitamin E) in oil-based cosmetic products, focusing on the evaluation of the sorptive capacity of human skin and the uniformity of the distribution of the preparation on its surface. The procedure is designed to determine vitamin E after application as an oil solution, relying solely on the analyte’s absorption without additional reagents, such as ascorbic acid or an alkali. The procedure involves vitamin E extraction with isopropanol and measuring an analytical signal by UV spectrophotometry. The calibration curve exhibits linearity within the range 0.02–0.1 mg of vitamin E/mL. The limit of detection for vitamin E, calculated from the calibration curve equation and its slope, is 0.5 µg/mL. This procedure has demonstrated reproducibility, selectivity, rapidity, and simplicity.

A method for the determination of phthalates in water is validated. It includes the sorption of hydrophobic components of a sample on a liquid chromatography column and the separation of analyte concentrated by online reversed-phase HPLC: for the quantitative determination of priority phthalates (PPhs) in surface waters at a trace level; qualitative assessment of the ratio of stable carbon isotopes ¹³C/¹²C in the PPh composition. It is shown that there is no contribution of PPhs from the laboratory background to the measurement results. The limits of determination (0.15−0.22 μg/L) and the accuracy of the determination (±δ = 10−20%) are found using online reversed-phase HPLC and the UV detection of the analytes. The boundary values for the ¹³C/¹²C isotope ratio are substantiated for a qualitative assessment of the results of measuring the Δ¹³C value in the structure of di(2-ethylhexyl) phthalate and its ingress into waters of Lake Baikal from biogenic and abiogenic sources is revealed. A procedure for determining PPhs by reversed-phase HPLC with online UV detection is tested in the field using a portable liquid chromatograph; the concentration ranges for di-n-butyl phthalate (from <0.15 to 1.6 μg/L) and di(2-ethylhexyl) phthalate (from <0.22 to 1.6 µg/L) in the coastal zone of Lake Baikal are evaluated.

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.