Journal of Analytical Chemistry最新文献

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%.

Magnetic nanoparticles of magnetite (MNPs) with surfaces modified by biocompatible cationic polyelectrolytes polyethyleneimine (PEI) and chitosan (CS) are synthesized by the chemical coprecipitation method. The magnetic nanoparticles were characterized by transmission electron microscopy and measurements of zeta (ζ) potential. The initial MNPs exhibit shapes close to spherical, with an average size of 10 ± 3 nm. The immobilization of a polyelectrolyte on the surface of MNPs results in the formation of aggregates with an interconnected porous network (shell) around individual particles with average sizes of 12 ± 2 nm for Fe₃O₄@PEI and 15 ± 2 nm for Fe₃O₄@CS, respectively. The effect of various experimental parameters, such as pH, extraction time, amount of adsorbent, and initial concentration of the dye, on the adsorption and desorption of food azo dyes Allura Red AC (E129) and Black Brilliant BN (E151) has been thoroughly investigated. The results demonstrate that, under optimal conditions, the recovery of these dyes from aqueous solutions reaches 96–100%, at a concentration factor of 2.7 × 10³ and adsorption capacities of 56 and 94 mg/g for Fe₃O₄@PEI, and 46 and 69 mg/g for Fe₃O₄@CS for E129 and E151, respectively. A comparison of the adsorption isotherms and kinetics of the process indicates that the Langmuir model and pseudo-second-order kinetics are preferable for describing the dye adsorption process. In the acidic and neutral pH ranges, electrostatic interactions primarily drive the adsorption process, while in the alkaline region, hydrogen bonding and hydrophobic interactions also play significant roles. The proposed adsorbents can be utilized for both the adsorption and preconcentration of the dyes in chemical analysis and the treatment of wastewaters for the dye removal. The preferred material for use is polyethyleneimine-modified nanomagnetite, which enables the adsorption and preconcentration of dyes across a wide pH range of 6–9.

A rapid and an environmentally friendly method is developed for the microextraction of furan derivatives from transformer oil for their determination by high-performance liquid chromatography with ultraviolet spectrophotometric detection. Various hydrophilic eutectic solvents were studied as extractants to implement vortex-assisted dispersive liquid–liquid microextraction. The results indicate that a three-component eutectic solvent composed of choline chloride, acetic acid, and water achieves the highest recoveries, ranging from 85 to 96%. The rapid spontaneous phase separation eliminated the need in centrifugation. Limits of detection (3σ) were achieved between 1 and 5 µg/L.

A voltammetric DNA sensor has been developed to detect DNA damage from calf thymus by measuring changes in redox signals in cyclic voltammograms of poly(Acridine Orange) (PAO) coatings. This polymer was synthesized on a carbon printed electrode from deep eutectic solvents—reline and glyceline—and a phosphate buffer solution. The optimal conditions for immobilizing DNA on each of the polymer coatings have been found. The effect of the polymerization medium on the electrochemical characteristics of the polyacridine dye layer and the polymer sensitivity to the thermal and oxidative damage of DNA has been identified. With the optimal composition of the surface layer the DNA sensor based on poly(Acridine Orange) synthesized from aqueous media (PAO1) reliably detected only chemical DNA oxidation. In contrast, the PAO synthesized from reline (PAO2) and glyceline (PAO3) demonstrated increased sensitivity to the incorporation of calf thymus DNA, which allows to discriminate between native, thermally denatured, and chemically oxidized DNA.

The application of nanostructured adsorbents in sample preparation (extraction and preconcentration) of multicomponent mixtures in the solid-phase extraction of organic compounds is gaining significant interest. This study examines the adsorption properties of ordered mesoporous analogues of SBA-15, synthesized in the presence of quercetin as a potential adsorbate. The work explores the specific features of the adsorption-based recovery and preconcentration of quercetin, dihydroquercetin, naringin, and rutin under dynamic conditions from acetonitrile solutions using the breakthrough curve method. The use of the generalized optimization criterion of adsorption preconcentration CE, within the framework of the Venitsianov–Tsysin model of dynamic adsorption preconcentration, taking into account the limiting (mixed-diffusion) stage of adsorption kinetics, enabled the evaluation of the efficiency of the adsorption preconcentration of flavonoids on the studied adsorbents. The results demonstrate that the use of ordered silica synthesized in the presence of a potential adsorbate significantly enhances concentration efficiency compared to nonstructured silicas or unmodified SBA-15 analogue samples.