Journal of Analytical Chemistry最新文献

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.

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.

One of current areas of application of microfluidic paper-based analytical devices (μPADs) is the determination of biologically active substances in various samples, including pharmaceuticals. Such determination is often carried out as screening analysis to identify samples that should be examined in more detail by highly informative, but relatively expensive methods. In this paper, an original method for the colorimetric determination of quercetin is proposed using microfluidic analytical systems based on paper modified with gold and silver nanoparticles of various morphologies. It is based on the reduction of silver(I) ions to metallic silver under the action of quercetin with a contrasting change of the color of the μPADs detection zones. A possibility of using a monitor calibrator and a smartphone camera for recording the analytical signal is demonstrated. Optimal conditions for the analysis are selected. It is shown that the type of nanoparticles affects the sensitivity of quercetin determination, which offers promise for creating multisensor systems for discriminating complex samples. The limits of detection for quercetin under the selected conditions are 70–120 ng, depending on the nature of the analytical reagent and the method of recording the analytical signal. The analytical range is 2–10 μg. The sample volume sufficient for analysis does not exceed 25 μL. The selectivity of the proposed method for determining quercetin with respect to a number of common inorganic ions and organic substances is assessed. The applicability of the developed approach to determining quercetin in three pharmaceutical preparations is shown.

High-performance liquid chromatography-tandem triple quadrupole mass spectrometry was validated to analyze acrylamide in coffee samples. Under optimal conditions, the quantitative range for acrylamide was 50–1000 µg/L, and the method detection limit was 30 µg/L. The recovery ranged from 85.2 to 97.3%, with high repeatability and reproducibility. The measurement uncertainty of the method was calculated using a top-down approach and determined to be 12.3%. The validated method was then applied to analyze 68 samples of roasted coffee beans collected from markets in Ho Chi Minh City. The results showed that 51.5% of the samples contained acrylamide at concentrations ranging from 51 to 560 µg/kg, and 10.3% had acrylamide contamination exceeding the maximum acceptance level. The results also demonstrated that the acrylamide contamination level in medium-roast coffee was much higher than that in light-roast and dark-roast coffee. The observation indicates that the level of acrylamide contamination of roasted coffee sold in Ho Chi Minh City markets is an excellent concern for food safety and quality management.

The present review provides a comprehensive overview of the development of analytical methodologies that are well-developed and validated for the estimation of memantine. Memantine is an N-methyl-D-aspartate receptor and is widely used for dementia, Parkinson’s disease, pervasive developmental disorders, schizophrenia, and alcohol abuse disorder. However, the estimation of memantine continues to attract researchers' attention due to its unique chemical properties. Memantine is a saturated compound belonging to biopharmaceutics classification system Class I, due to its high solubility and permeability. However, its lack of unsaturation makes direct detection using ultraviolet-visible (UV-Vis) spectroscopy challenging. Consequently, various analytical approaches have been developed and validated for the detection of memantine, including UV-Vis spectroscopy, fluorescence spectroscopy, infrared spectroscopy, voltammetry, potentiometry, liquid chromatography, gas chromatography, nuclear magnetic resonance spectroscopy, and other hyphenated techniques. This paper provides comprehensive insights for analysts interested in developing analytical methods.