Journal of Analytical Chemistry最新文献

Kraft (sulfate) lignin is a large-scale by-product of the pulp and paper industry and a promising renewable raw material for the production of a wide range of chemicals and materials with high added value. One of the main directions of valorization of technical lignin is conversion into low-molecular-weight phenolic products using various depolymerization methods. To solve the problems of operational control of ongoing processes and the molecular level characterization of complex mixtures of formed low-molecular-weight compounds, this study proposes the use of atmospheric pressure photoionization high-resolution mass spectrometry in combination with visualizing the resulting data sets based on elemental ratios (van Krevelen diagrams) and Kendrick mass defects. Using this methodology, the kraft lignin depolymerization products formed in a supercritical isopropanol medium were characterized, and the effect of additives of nitrogen-containing catalysts (hydroxylamine and diethylamine) on the ongoing processes and the composition of the resulting products were studied. The leading role of reduction processes in the transformation of lignin oligomers under the action of isopropanol was shown, and the characteristic differences between the products obtained in the absence and with the addition of nitrogen-containing catalysts were revealed.

A new approach to detecting dibenzothiophene-5,5-dioxides by soft mass spectrometry methods has been developed. This method involves the chemical modification of target compounds with phenols in the presence of trifluoroacetic anhydride to form organic salts. The cations of these salts are easily desorbed under matrix-assisted laser desorption/ionization (MALDI) conditions and extracted by electrospray ionization (ESI). Upon collisional activation, the derivatization products eliminate the aryl oxy substituent from the sulfur atom, enabling the detection of derivatization products through selected reaction monitoring.

Misuse of chloramphenicol (CAP) could lead to its residue in animal-sourced food and subsequently harm human health through the food chain. Therefore, it is urgently needed to effectively determine CAP residues in animal-sourced food. Here, an easily operated target recycling strategy for the determination of CAP was developed based on a CAP-specific aptamer. The CAP-specific aptamer was hybridized with a complementary short chain modified with fluorescent and quenching groups at both ends. Upon addition of CAP, the aptamer would be separated from its complementary probe and bind with CAP. The fluorescent and quenching groups labeled on the complementary probe were separated by exonuclease I (Exo I) digestion to release a fluorescent signal. Meanwhile, Exo I also digested the aptamer, and CAP was released from the complex, triggering the determination signal amplification based on CAP recycling. Factors (i.e., NaCl concentration and Exo I digestion time) that would affect the determination performance of this sensor system were optimized. Under the optimized conditions, the developed sensor system exhibited high determination sensitivity toward CAP with a limit of detection of 0.08 ng/mL (linear range from 0.1 to 5 ng/mL). Moreover, this sensor system was applied to determine CAP in real spiked milk, and the recovery rates ranged from 97.2 to 100.0%. Meanwhile, this sensor system also suggested cost efficiency with a determination cost of only $0.29 per sample. Results presented here and the high specificity of the aptamer suggested by the previous work indicated the application potential of this developed aptamer-based sensor system for the determination of CAP residue in animal-sourced food.

Several techniques are available to determine an analyte, but the most preferred technique is fluorescence-based sensing owing to its sensitivity and selectivity. One of the main components of fluorescent-based sensors is a filter that allows a specific range of wavelengths to pass through and reach the sensing element. Existing filters still lack certain aspects such as durability, interference, cost, integration with a sensing element, biocompatibility, etc. This research aims to design and develop a polyvinyl acetate (PVAc)-benzophenone-based emission filter by spin coating and integrating it with a complementary metal-oxide semiconductor imaging sensor for use as a portable biochemical sensing device. In addition, the fabricated filter is intended to allow the conjugation of recognition elements necessary for biosensing using plasma oxidation. In this study, PVAc and benzophenone concentrations were optimized to fabricate an emission filter (EF) with precise thickness and uniformity. Subsequently, the fabricated EF underwent analysis using a single-beam UV-Vis spectrophotometer. Additionally, plasma treatment was administered to the EF, enabling further examination using fluorescein isothiocyanate dye under a fluorescent microscope. These examinations collectively suggest that the prepared filter possesses dual properties, i.e., it not only serves as an emission filter but also facilitates surface modification through plasma oxidation for the conjugation of chemical groups that can selectively bind to target analytes for biosensing purposes.

A new, fast, and environmentally friendly method based on ultrasound-assisted extraction combined with dispersive liquid-liquid microextraction using a low-density solvent was developed and optimized for assessing the levels of fenvalerate in strawberry samples. Variables affecting the performance of both steps were thoroughly investigated. Under the optimum conditions, relative recoveries for strawberry samples were in the range of 88.0–98.0%. The calibration graph was linear in the range of 10–1000 µg/kg, and the limits of detection and quantification were 3 and 10 µg/kg, respectively. The relative standard deviation for 40.0 µg/kg of fenvalerate in strawberry samples was 8.1% (n = 5). The obtained results show that the proposed method is a fast and simple method for the determination of fenvalerate in strawberry samples.

A micelle-mediated cloud point extraction for carbendazim determination in vegetable and environmental samples using UV-Vis spectrophotometry was developed. Parameters of the proposed method (i.e., pH, extraction time, concentration of surfactant, concentration of ferricyanide, concentration of ferric chloride, extraction temperature, and sample volume) were optimized by UV-Vis spectrophotometry. In this study, the developed method was based on the oxidation reaction of carbendazim by the ferric ion (Fe³⁺) under acidic conditions, combined with potassium ferricyanide (K₃[Fe(CN)₆]) to form potassium hexacyanoferrate complexes or the Turnbull’s blue product quantitatively. The final products were solubilized into surfactant micelles, and carbendazim was determined by UV-Vis spectrophotometry at 685 nm after cloud point extraction. The analytical performance of the proposed method was obtained under optimal conditions. The limits of detection and quantification were found to be 0.12 and 0.41 mg/L, respectively. Precision factors were expressed as intra-day (1.6%) and inter-day (7.2%) variations over three replications. Furthermore, the proposed method was applied to the determination of carbendazim in environmental samples such as tap water, underground water, surface water, and in vegetable samples such as garlic, shallot, dried chili, celery, and peanuts. Recovery was obtained in the range of 83–113%.