Journal of Analytical Chemistry最新文献

Specific features of the preconcentration and determination of polycyclic aromatic hydrocarbons (PAHs) in humus-rich soils by gas chromatography–mass spectrometry (GC–MS) are studied. The QuEChERS technique and dispersive liquid–liquid microextraction (DLLME) were employed to extract PAHs from soils using acetone and binary extractants of various compositions, including acetonitrile–dichloromethane, acetonitrile–acetone, acetone–hexane, acetone–chloroform, acetone–dichloromethane, and ethyl acetate–dichloromethane. Recoveries of low- and medium-molecular-weight PAHs using these solvent mixtures reached approximately 100%, while the acetone–dichloromethane mixture yielded over 90% recovery for high-molecular-weight PAHs. Under optimized GC–MS conditions with QuEChERS extraction, the limits of quantification (LOQ) for fluoranthene, pyrene, chrysene, and triphenylene reached 5 µg/kg, and for the remaining PAHs, 10 µg/kg in humus-rich soils. It was shown that the reliable GC–MS determination of lower concentrations of PAHs requires both the elimination of the matrix effect and the preconcentration of the analytes. The sequential application of QuEChERS and DLLME techniques enabled a decrease in the limits of quantification by GC–MS to 1.8 µg/kg for fluoranthene, pyrene, chrysene, and triphenylene, and to 3.5 µg/kg for the remaining PAHs. The optimized procedure for PAH determination in humus-rich soils was validated using real chernozem samples.

A method is proposed for matrix separation from a sample of tellurium dioxide TeO₂ as tellurium tetrachloride based on reactive distillation in a flow reactor at 240°C using gaseous chlorine as a chlorination agent. The behavior of 59 impurities is studied, and it was found that As, Au, B, Bi, Cu, Ga, In, Mo, Nb, Pb, Re, Ru, Sb, Se, Sn, Ta, Ti, V, W, and Zn were lost completely or partially, whereas Ag, Al, Ba, Be, Ca, Cd, Ce, Co, Cr, Dy, Er, Eu, Gd, Ir, Hf, Ho, K, La, Li, Lu, Mg, Mn, Na, Nd, Ni, P, Pd, Pr, Pt, Rb, Rh, Sc, Sm, Sr, Tb, Tm, Y, Yb, and Zr were retained in the concentrate by more than 75%. The impurity content of the concentrate was determined by inductively coupled plasma atomic emission spectrometry. Accuracy was confirmed by the spike experiment and by comparison with the results of analyses without preconcentration. The limits of detection are in the range from 2 × 10^–8 to 8 × 10^–6 wt %, intralaboratory precision is better than 31%.

A simple and a rapid procedure for the gas-chromatographic determination of ethanol in soft drinks is proposed (kvass, grape juice, non-alcoholic beer) based on the headspace microextraction of an analyte into a drop (1 μL) of distilled water located above the surface of the analyzed liquid on the tip of a needle of a standard microsyringe for gas chromatography. The limit of detection for ethanol is (3–6) × 10^–5 vol %, the time of a replicate determination, including headspace extraction, does not exceed 5 min. 2-Propanol, not detected in the beverages, is used as an internal standard. The accuracy of the procedure is confirmed by the added–found method, the relative standard deviation does not exceed 7% at the ethanol concentration in the sample 10^–2 vol %.

Pyrazole-derived Schiff bases are mostly designed for the optical sensing of ionic species. In this research, a pyrazole-based Schiff base, 4-(4-methoxybenzylideneamino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (MBz-AAP), has been studied for its optical sensing properties towards various ionic species, including heavy metal ions and anions. Among these species, this probe exhibits a color change from colorless to maroonish-red for Fe²⁺ and Cu²⁺ ions, and colorless to yellow for ({text{HSO}}_{4}^{ - }) ions. These optical changes are found to be consistent with red shifts in the ultraviolet-visible absorption spectrum of MBz-AAP from 334 to 504, 510, and 387 nm for Fe²⁺, Cu²⁺, and HSO₄^– ions, respectively. Limits of detection (LOD) of MBz-AAP for Fe²⁺, Cu²⁺, and ({text{HSO}}_{4}^{ - }) ions are calculated to be 2.45, 3.34, and 2.24 μM, respectively. These LODs for Fe²⁺ and Cu²⁺ are much lower than their allowable limits in drinking water, i.e., 5.36 and 31.5 μM, respectively. Moreover, the stoichiometric binding ratios of Fe²⁺, Cu²⁺, and ({text{HSO}}_{4}^{ - }) with MBz-AAP are determined to be 1 : 1, with binding constants of 5.0 × 10³, 1.6 × 10³, and 7.05 × 10³ M^–1, respectively.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus that has been identified as the causative agent of an ongoing global pandemic of acute respiratory distress syndrome, coronavirus disease 2019. Ranked as one of the top priorities is developing an accurate, reliable, and affordable laboratory diagnostic test for pathogen detection to facilitate disease tracking. In this study, a multiplex-based assay to detect SARS-CoV-2 using four primers/probes to amplify regions of the spike (S), nucleocapsid (N), and envelope (E) protein-coding genes, along with amplifying region of the 3' untranslated region (UTR) was designed and developed. To provide accurate detection of different SARS-CoV-2 variants, an in silico design and validation pipeline was utilized. These included multi-sequence alignments with Clustal Omega, specificity verification by the Basic Local Alignment Search Tool (primer-BLAST), and computational performance verification using Biopython. The primers and hydrolysis probes designed were experimentally tested against more than two million SARS-CoV-2 genome sequences obtained from the National Center for Biotechnology Information Virus Database, with >97% specificity across 2200 lineages, including all of the significant variants of concern and variants of interest. The experimental validation phase included synthetic SARS-CoV-2 constructs and ribonucleic acid samples from nasopharyngeal swabs of 20 patients, including both symptomatic and asymptomatic cases. The assay displayed 100% sensitivity and specificity, with the limit of detection as low as 10 copies/mL, which surpassed the detection limits of some commercially available reverse transcription quantitative polymerase chain reaction (RT-qPCR) kits. Amplification efficiency was optimized for all targets, ranging from 94.92% for the N gene, 98.84% for the S gene, 81.75% for the E gene, to 82.14% for the 3′UTR genes. Assay selectivity was verified by cross-reactivity against common respiratory viruses—SARS-CoV-1, Middle East respiratory syndrome coronavirus, Influenza A/B, and human coronaviruses (HCoV-229E, HCoV-NL63, HCoV-OC43, and HCoV-HKU1)—and no off-target signal was observed. The ability to detect multiple genomic regions renders the assay resilient to mutation-based primer mismatch, making it extremely suitable for clinical diagnostics, epidemiological surveillance, and variant monitoring.

The chromatographic retention of alcohols, ketones, alditols, and carbohydrates on a cation exchanging column (200 × 4.6 mm, Sevko AA) packed with sulfonated poly(styrene-divinylbenzene) with a crosslinking degree of 10% and a particle diameter of 7 μm saturated with various counterions (H⁺, Ca²⁺ and La³⁺) is studied in the ligand exchange chromatography version. The sorbent in the Ca²⁺ form shows higher retention times and selectivity in the separation of carbohydrates and ethylene glycols. The sorbent in the La³⁺ form provides a strong retention and a better selectivity for the separation of alditols. A possibility of using this column for determining carbohydrates in food products (juice, honey) using refractometric detection is shown.

Micromixers are widely employed within the domains of biochemistry, drug delivery, and biomedical applications, among others. The phenomenon of induced-charge electroosmosis has garnered significant attention from the microfluidic research community over the past decade. The model put forth leverages the principles of electroosmosis to enhance the process of fluid mixing. This system incorporates a time-varying electric field, wherein the resulting electroosmosis disturbs the parallel streamlines that are characteristic of the otherwise highly organized laminar flow regime. A sinusoidal electric potential of 0.1 V and a frequency of 9 Hz are applied across the electrodes. In order to further augment the mixing efficiency, two congruent obstacles are judiciously positioned within the channel. The findings indicate that the micromixer exhibits an impressive mixing efficiency approaching 95% and possesses potential applications across diverse fields, including biochemistry and the biomedical sciences.

The residual concentration of the organochlorine pesticide lindane in model samples of tomatoes, cucumbers, and onions is studied by gas chromatography. A pesticide solution was added to soil, after which these plants were grown twice in the contaminated soil. Two sample preparation methods were used in the analysis: according to GOST 30349 and a similar procedure using liquid nitrogen at the homogenization stage. It was found that the use of liquid nitrogen in the sample preparation increased the recovery of the analytes by up to two times. For tomato and cucumber samples, it was found that both during primary and secondary plant cultivation, the residual amount of organochlorine pesticide increased with increasing pesticide concentration in spraying. However, this is not typical for onion samples. In the last case, the residual amounts of lindane decreased with increasing concentration of the initial analyte. Such behavior is typical for root crop samples, which do not include onion. The residual concentration of lindane in different parts of tomato and cucumber plants varied: tomato accumulated the pesticide to a greater extent in the fruit, and cucumber, in the tops. In re-cultivation in contaminated soil, the residual amount of lindane did not exceed 12% of the initial one. As a result, it was found that the most suitable plant for growing on lindane-contaminated soils is cucumber, because 80–90% of lindane is accumulated in inedible cucumber roots, and the fruits contain the smallest amount of the pollutant among all vegetables. Tomato is unsuitable for growing on contaminated soils, because the fruits accumulate significant amounts of lindane.

New modifiers of electrophoretic systems—cationic polyelectrolytes with micellar properties, i.e. poly-11-acryloyloxyundecyl-N-methylpiperidinium bromide (pAUMP-Br), poly-11-acryloyloxyundecylpyridinium bromide, poly-11-acryloyloxyundecyl-1,4-diazabicyclo[2.2.2]octane-1-ium bromide, and a chiral copolymer based on acylated quinine and N-(11-acryloyloxyundecyl)-N-methylpiperidinium bromide (pAUMP–AQin)—have been synthesized. The electrophoretic properties of these polymers have been studied in the separation model mixtures of biologically active substances, steroid hormones, biogenic amines, and amino acids, in micellar electrokinetic chromatography and capillary electrochromatography modes. It was found that the new polyelectrolytes are polyfunctional modifiers of quartz capillary walls and the background electrolyte and ensure the implementation of various modes of electrophoretic separation of biologically active substances, indirect detection in the presence of a chromophore group in the polymer, generation of an anodic electroosmotic flow, and governing the efficiency and selectivity of the analyte separation. Field-amplified sample stacking in a quartz capillary modified with pAUMP-Br was performed, which ensured the 15-fold preconcentration of biogenic amines and reduced the limits of detection. It was found that the pAUMP–AQin copolymer with a chiral label favors the separation of tryptophan enantiomers.

The objective of this study is to utilize novel hybrid biomaterials, comprising glucose oxidase coated with an alkyl-modified silica polymer shell in conjunction with a Clark oxygen electrode, as biocatalysts. This work studied the efficiency of immobilization of glucose oxidase in a sol-gel matrix based on the silane precursors tetraethoxysilane, methyltriethoxysilane, and diethoxydimethylsilane. The use of a 50/50 vol % mixture of methyltriethoxysilane and tetraethoxysilane produces a polymer material with smaller pores compared to a mixture of other silane precursors. When precursors are added during the formation of the material with non-hydrolyzed bonds, the surface area of the materials increases from 40 m²/g when using only tetraethoxysilane to 70 m²/g with a mixture of diethoxydimethylsilane and tetraethoxysilane, and up to 110 m²/g with a mixture of methyltriethoxysilane and tetraethoxysilane. In addition, adding diethoxydimethylsilane to the tetraethoxysilane system increases the pore volume from 0.008 to 0.09 cm³/g, and adding methyltriethoxysilane increases the pore volume to 0.33 cm³/g. A biosensor using glucose oxidase immobilized in a polymer matrix based on a diethoxydimethylsilane/tetraethoxysilane 50/50 vol % mixture is characterized by a high sensitivity coefficient of 3.8 mg O₂/min mmol and a glucose concentration range of 1–280 mmol/L. Therefore, this study demonstrates that the use of polymers with linear fragments is more effective for the immobilization of glucose oxidase compared to traditional immobilization methods. This could lead to the development of new and efficient enzyme immobilization methods for the determination of individual substances in biological fluids, e.g., blood glucose.