Journal of The Chinese Chemical Society最新文献

This special issue on “Frontier Precise Measurement” aims to highlight the latest developments and applications in this dynamic area of research. In this special issue, we have invited chemists from a broad range of disciplines and expertise to showcase the diversity and activity of chemical and biological measurement. The issue features a diverse collection of articles covering various topics in precision measurement, including extraction, spectroscopy, sensors, electrochemical detection, mass spectrometry, and software development. We hope that readers will thoroughly enjoy the content.

Antibiotics are frequently used as growth boosters in animal husbandry. Tetracyclines (TCNs) are among the most widely used antibiotics compared to others, leaving traces in animal-based foodstuffs like milk and meat. Thus, monitoring of TCNs is paramount, especially in the feedstuff. In the present study, a green method is developed to synthesize magnetic Ag/GO-Fe₃O₄ nanocomposites using Azadirachta indica leaf extract. The synthesized adsorbent (Ag/GO-Fe₃O₄) was analyzed for the residual extraction of oxytetracycline (OTC) and chlortetracycline (CTC) from the fresh milk samples through the magnetic solid-phase extraction principle. The extraction procedure involved the deproteinization of milk, spiking with antibiotics, followed by magnetic solid-phase extraction and quantification of TCNs by HPLC with a UV detector. Different factors that affected the adsorption capacity of the adsorbent for the TCNs like pH, temperature, amount of nanocomposite, and time were studied. The inter-day and intra-day precision were calculated for OTC (4% and 6%) and CTC (3% and 4%), respectively. The limit of detection and quantification for OTC was 0.5 and 1.5 μgL⁻¹ and for CTC was 0.2 and 0.6 μgL⁻¹ respectively while the percentage extraction was 94%–96%.

An amperometric sensor for ascorbic acid determination has been developed by modifying the surface of a glassy carbon electrode (GCE) with polyaspartic acid (PolyAsp), carboxylated multi-walled carbon nanotube (c-MWCNT), and ionic liquid (IL, 1-butyl-3-methylimidazolium hexafluorophosphate). The amount of each modification material on the surface was optimized in order to achieve good analytical performance. The operating conditions of c-MWCNT−IL/PolyAsp/GCE were optimized. The performance characteristics of c-MWCNT−IL/PolyAsp/GCE were investigated at optimum pH (8.0) and optimum potential (+0.20 V), and the sensor responded linearly to ascorbic acid between 5.3–2766.3 μM with a sensitivity of 19.64 μA mM⁻¹ and detection limit of 3.0 μM. Determination of ascorbic acid in vitamin C tablet, vitamin C injection solution, and orange juice was successfully performed with the presented sensor and the recovery values were found between 98.9% and 101.6%.

The application of iron oxide quantum dots (IOQDs) in this study led to the development of a straightforward, easy, and selective approach for cytosine sensing. To examine the capability of IOQDs in detecting nucleobases, attempts have been made to gain insight into the characteristics of IOQDs, including UV/Vis spectroscopic analysis, infrared spectroscopy, fluorescence spectroscopy, transmission electron microscopy, and powder-XRD. We introduced IOQDs with a mean particle size distribution of 5.71 ± 0.08 nm for detecting cytosine by harnessing a turn-on fluorescence phenomenon. The fostering fluorescence response of IOQDs was triggered in the presence of cytosine. In comparison, the presence of other nucleobases did not further induce the fluorescence signal of IOQDs. It was concluded that the hydrogen bonding bridging the carboxylate and hydroxyl groups on the surface of QDs with the amine groups of cytosine results in the elevation of IOQDs fluorescence.

A new sensor was fabricated for the determination of ketamine (Ket) in urine samples based on enhanced electrochemiluminescence (EECL) behavior of luminol on a carbon paste electrode (CPE) modified with the conductive molecularly imprinted polymer (CMIP) film. The FESEM technique was applied to demonstrate the rod shape morphology of CMIP. Unlike the common luminol system, EECL signal of luminol no need to addition of hydrogen peroxide and it might find application in efforts to avoid instability of hydrogen peroxide or its interference with the analytes of interest. The EECL emission has been optimized by an investigation of the applied potentials, electrochemical polymerization conditions, template and modifier concentrations, and the pH solution. Under the optimum conditions, the EECL signal depended linearly on the Ket concentration within a range from 0.1 to 1.25 μM with a limit of detection (LOD) of 0.08 μM. The sensor exhibited very good recovery percentages ranging from 92% to 101% in urine samples, while precisions were ≤3%. These results suggested that the proposed sensor would be applicable for analysis Ket in complex matrixes without interfering of other drugs (anesthetics) and thus has the potential to be used in clinical application.

An efficient calculation tool for rigorously optimizing the instrument parameters of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is demonstrated in this work. Optimization of MALDI-TOF MS has been an experience-based, time-consuming process without a rigorous theoretical principle. Based on the comprehensive calculation model reported previously, we developed a software tool, MAXTOF, to rapidly determine instrument parameters providing ultimate mass resolving power (MRP). The software conducts big data analysis of most instrument parameters to predict the MRP, including instrument dimensions, voltages, mass-to-charge ratio of ions, and ion extraction delay. It can complete the calculation in seconds, providing parameters that serve as the starting point for subsequent optimization that greatly accelerates the optimization process. Experimental validation using a commercial instrument demonstrates MAXTOF's efficacy in predicting optimal parameters and enhancing MRP. The predicted ion extraction delays for bradykinin fragment, P₁₄R polypeptide, and insulin chain B ions were within 5% of the values observed through long-term optimization. The observed MRP of those ions ranged from 2800 to 4500. Results show that the method and software are highly advantageous for fast and precise measurements.

Smart polymers undergo significant physical or chemical changes in response to stimuli like temperature and pH. Achieving a narrow molecular weight distribution is crucial for their sensitivity. Reversible addition–fragmentation chain transfer (RAFT) in ionic liquids is an effective method for synthesizing such polymers due to its favorable kinetics and environmental benefits. Most studies use imidazolium ionic liquids, while pyridinium ionic liquids are less common despite their easy synthesis. This study reports the first successful RAFT copolymerization of di(ethylene glycol) methyl ether methacrylate (DEGMEMA) and methyl methacrylate in N-hexylpyridinium hexafluorophosphate ([HPY][PF₆]). Both linear and hyperbranched copolymers (M_n > 25,000) with narrow molecular weight distribution were synthesized, showing observable temperature responses and biocompatibility. The linear copolymers had a desirable dispersity (Ð) of less than 1.10, while the hyperbranched copolymer had a Ð of 2.034. The lower critical solution temperatures (LCSTs) of the copolymers were close to or below the LCST of PDEGMEMA (26°C). This study indicates that pyridinium ionic liquids can be explored as a suitable solvent for synthesizing methacrylate-based smart polymers.