WESSLING GmbH , Haynauer Straße 60 , D-12249 Berlin ; Germany.
Eastern Regional Research Center, Agricultural Research Service , United States Department of Agriculture , 600 East Mermaid Lane , Wyndmoor , Pennsylvania 19038 , United States.
J Agric Food Chem. 2019 Aug 21;67(33):9203-9209. doi: 10.1021/acs.jafc.9b04006. Epub 2019 Aug 12.
With the monitoring of hundreds of pesticides in food and feed, the comminution step is equally crucial as any other to achieve valid results. However, sample processing is often underestimated in its importance and practical difficulty to produce consistent test portions for analysis. The scientific literature is rife with descriptions of microextraction methods, but ironically, sample comminution is often ignored or dismissed as being prosaic, despite it being the foundation upon which the viability of such techniques relies. Cryogenic sample processing using dry ice (-78 °C) is generally accepted in practice, but studies have not shown it to yield representative test portions of <1 g. Remarkably, liquid nitrogen has rarely been used as a cryogenic agent in pesticide residue analysis, presumably as a result of access, cost, and safety concerns. However, real-world implementation of blending unfrozen bulk food portions with liquid nitrogen (-196 °C) using common food processing devices has demonstrated this approach to be safe, simple, fast, and cost-effective and yield high-quality results for various commodities, including increased stability of labile or volatile analytes. For example, analysis of dithiocarbamates as carbon disulfide has shown a significant increase of thiram recoveries (up to 95%) using liquid nitrogen during sample comminution. This perspective is intended to allay concerns among working laboratories about the practical use of liquid nitrogen for improved sample processing in the routine monitoring of pesticide residues in foods and feeds, which also gives promise for feasible test sample size reduction in high-throughput miniaturized methods.
在对食品和饲料中的数百种农药进行监测时，粉碎步骤与其他任何步骤一样至关重要，才能获得有效的结果。然而，样品处理在实际操作中往往被低估了其重要性和难度，因为它是为分析生成一致测试部分的关键。科学文献中充斥着各种微萃取方法的描述，但具有讽刺意味的是，尽管粉碎是这些技术可行性的基础，但它经常被忽视或视为平凡无奇。在实践中，使用干冰（-78°C）进行低温样品处理通常是被接受的，但研究表明，这种方法无法获得<1 克的有代表性的测试部分。值得注意的是，液氮在农药残留分析中很少被用作低温试剂，可能是因为获取、成本和安全方面的考虑。然而，使用常见的食品加工设备将未冷冻的散装食品部分与液氮（-196°C）混合的实际实施情况表明，这种方法安全、简单、快速且具有成本效益，并为各种商品（包括不稳定或易挥发分析物的稳定性增加）提供高质量的结果。例如，在分析二硫代氨基甲酸盐作为二硫化碳时，在样品粉碎过程中使用液氮可以显著提高福美双的回收率（高达 95%）。本观点旨在消除工作实验室对在食品和饲料中常规监测农药残留时使用液氮进行样品处理的实际应用的担忧，这也为在高通量微型化方法中减少可行的测试样品量提供了希望。
