In recent years, microchemical devices have garnered increasing attention for enabling highly efficient chemical processes using minute sample volumes while offering advantages such as compactness and low environmental impact. In this study, a rotating microfluidic device capable of processing sample volumes on the order of several hundred microliters was developed utilizing centrifugal force as the driving mechanism. The device was designed to streamline labor-intensive solid-phase extraction (SPE) procedures commonly used in food analysis pretreatment. A centrifugal microfluidic device featuring a conditioning unit for SPE column preparation and a pretreatment unit for sample processing was developed. A validation study was conducted using this device on vitamin B1 (thiamine) retained on an SPE column. The measurement results met the relevant guidelines, and the method employing this device reduced processing time compared to conventional methods. As a preliminary evaluation, ascorbic acid 2-glucoside was also tested as a flow-through-mode analyte. However, device-associated chromatographic interference precluded confirmation of the quantitative validity of the method. Thus, this device is expected to contribute to labor and space savings as well as reduced environmental impact in food analysis pretreatment. However, further device design improvements and additional validation are required to expand its range of applicable targets.
In this work, a flexible and environmentally compatible thin film, consisted of cellulose and polypyrrole, was prepared and used as a new thin film microextraction sorbent for adsorption and determination of trace amount of methylnaphthalene, anthracene and pyrene from aqueous samples. Analytes were determined by gas chromatography equipped with a flame ionization detector. polypyrrole was used as a modifier due to its porous structure and good mechanical stability in aqueous solution. Pyrrole monomers deposited on cellulosic substrate were polymerized through oxidative chemical polymerization. Extraction of analytes from sample solution to the cellulose/poly pyrrole film was performed through π-π interactions between the sorbent and polycyclic aromatic hydrocarbons (PAHs). Extraction efficiency was studied by changing parameters such as desorption solvent, time of desorption, volume of desorption solvent, salt concentration, temperature and extraction time were optimized. The detection limits of 1.40, 0.60 and 0.45 µg L−1 were obtained for methylnaphthalene, anthracene and pyrene, respectively. The method showed good linearity in the concentration range of 4–3000, 2–1000, and 1–500 µg L−1 for methylnaphthalene, anthracene and pyrene, respectively. Intra- and inter-day precision were in the range of 6.0–8.0
Acrylamide (AA) is a highly polar compound that exhibits poor retention and low selectivity in conventional reversed-phase LC–MS analyses. To establish a derivatization-based LC–MS/MS method for AA, we evaluated the potential of 5-(dimethylamino)-N-(2-sulfanylethyl)naphthalene-1-sulfonamide (DNS-SH) as an effective derivatization reagent and compared its performance with that of other representative thiol reagents. The ionization efficiency, the formation of product ions during collision-induced dissociation, and the progress of the reaction—as analyzed by LC-MS (MS/MS)—were accurately evaluated based on the molar ratios determined by 1H-qNMR. The DNS derivative of AA (AA-DNS) exhibited a superior MS response than its other thiol derivatives, providing a 4–17-fold higher MS/MS signal intensity. In addition, computational studies indicate that DNS-SH has the potential to be a more effective derivatization reagent with higher reactivity. These results indicate that analytical performance is strongly influenced by the structural characteristics of thiol reagents, particularly their ionization efficiency and product-ion formation. The newly developed analytical method was applied to quantify AA in food additives subjected to heating during manufacturing, revealing that its concentration was negligible in these samples. This finding suggests that food additives contribute minimally to overall dietary exposure to AA. Thus, the proposed method provides a highly sensitive approach for determining AA.
In microjoule high pulse repetition frequency laser induced breakdown spectroscopy systems, the traditional single-variable parameter optimization method can only analyze the effects of scan speed and laser frequency independently, without considering the interaction effect between these two factors. To address this issue, an optimization strategy based on energy deposition rhythm (EDR) was proposed for the proportional optimization of scan speed and laser frequency. To begin with, the interaction between scan speed and laser frequency was analyzed using two-factor analysis of variance. Based on this, the effects of proportionally increasing scan speed and laser frequency on spectral signals were investigated by maintaining a constant ratio between the two parameters under different EDR conditions, followed by quantitative analysis based on the optimized spectral signals. The results indicated that, at a fixed EDR, proportional increases in scan speed and laser frequency maintained a constant spatial interval between adjacent laser pulses, thereby reducing the interference caused by pulse-spacing variations in local ablation overlap and related ablation conditions. Meanwhile, this proportional increase also resulted in a larger number of laser pulses contributing within the fixed 20 ms integration window owing to the increase in laser frequency, thereby enhancing the accumulated spectral emission while maintaining signal stability. The accumulated spectral intensities of Mg, Mn, and Fe increased by approximately 4–9, 5–10, and 4–10 times, respectively. The most pronounced quantitative improvement was observed under EDR = 1/400, where the R2 values for Mg, Mn, and Fe increased from 0.8826, 0.9516, and 0.9061 to 0.9745, 0.9722, and 0.9778. This study provides a simple and broadly applicable strategy for optimizing high pulse repetition frequency LIBS signals and improving multi-element quantitative analysis performance.
