Erdoğrul İlayda Yaman, Yalçın Şerife H
Chemistry Department, Faculty of Science, İzmir Institute of Technology, 35430, Urla, İzmir, Turkey.
Chemistry Department, Faculty of Science, İzmir Institute of Technology, 35430, Urla, İzmir, Turkey.
Talanta. 2026 Jan 1;296:128537. doi: 10.1016/j.talanta.2025.128537. Epub 2025 Jun 30.
In this study, a dried-droplet LIBS methodology for determining cadmium in cow milk has been developed. The performance of the methodology was shown by standard and real protein samples. A standard protein, bovine serum albumin (BSA), and whey protein extracted from skim cow milk were incubated in standard Cd solutions, and the complex solution was filtered through cut-off filters by centrifugation. The unreacted cadmium in the filtrate and Cd-bound protein in the filtered fraction were loaded separately onto a Si-wafer substrate and analyzed via dried-droplet LIBS methodology. Measurements were performed at reduced pressures by taking advantage of the signal enhancement effect. The optimum pressure for most Cd emission lines was found to be 100 mbar. It has been shown that the dried-droplet LIBS methodology at reduced pressures can be used for the identification and determination of free and protein-bound Cd in the whey matrix. The concentration-based detection limit of Cd bound to whey proteins was determined to be 20.2 ng mL, which corresponds to as low as 10 pg in absolute amount with a sample volume of 500 nL. The LOQ value is estimated as 67.3 ng mL and 33.3 pg, in terms of concentration unit and absolute amount, respectively. The use of small sample volumes is important in the analysis of limited amounts of samples, such as body fluids. Preconcentration studies with multiple loadings of the sample on the same spot resulted in improvements in concentration-based detection. 8 ng mL Cd in the whey matrix that could not be determined by a single droplet loading due to being below the detection limit; could be determined after 10 consecutive loadings. The methodology may also be applied to the determination of other toxic metals bound to proteins for food quality control.
在本研究中，开发了一种用于测定牛奶中镉的干滴激光诱导击穿光谱（LIBS）方法。该方法的性能通过标准和实际蛋白质样品得以展现。将标准蛋白质牛血清白蛋白（BSA）和从脱脂牛奶中提取的乳清蛋白在标准镉溶液中孵育，然后通过离心用截留滤器过滤复合溶液。滤液中未反应的镉和过滤部分中与镉结合的蛋白质分别加载到硅片基底上，并通过干滴LIBS方法进行分析。利用信号增强效应在减压条件下进行测量。发现大多数镉发射线的最佳压力为100毫巴。结果表明，减压下的干滴LIBS方法可用于鉴定和测定乳清基质中游离和与蛋白质结合的镉。与乳清蛋白结合的镉的基于浓度的检测限确定为20.2纳克/毫升，对于500纳升的样品体积，绝对量低至10皮克。定量限（LOQ）值分别按浓度单位和绝对量估计为67.3纳克/毫升和33.3皮克。在分析有限量的样品（如体液）时，使用小样品体积很重要。在同一点多次加载样品的预浓缩研究提高了基于浓度的检测效果。由于低于检测限，单次加载无法测定乳清基质中8纳克/毫升的镉；连续加载10次后可以测定。该方法也可应用于食品质量控制中与蛋白质结合的其他有毒金属的测定。
