Sampling and sample processing in pesticide residue analysis

Authors: Lehotay, Steven; COOK, JO MARIE - Florida Department Of Agriculture And Consumer Services

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2015
Publication Date: 2/12/2015
Publication URL: https://handle.nal.usda.gov/10113/61138
Citation: Lehotay, S.J., Cook, J. 2015. Sampling and sample processing in pesticide residue analysis. Journal of Agricultural and Food Chemistry. DOI: 10.1021/jf5056985.

Interpretive Summary: Just as a chain is only as strong as its weakest link, the overall quality of the analytical process is limited by the least accurate step in the analysis. Typical quality assurance and control practices in pesticide monitoring laboratories do not address the sampling and sample processing steps, but if the sample collection and homogenization steps are not conducted properly, the analysis will not provide meaningful results, no matter the accuracy of the subsequent analysis. In fact, results that provide false confidence of precision and trueness are misleading and potentially cause worse decision-making based on the results. In this perspectives article, the authors review the critical but often-neglected aspects of sampling and sample processing, and present real-world results to demonstrate the degree of uncertainty in the different steps in the analytical process. The authors evaluate current state-of-the-art practices related to sample miniaturization for use in automated high-throughput methods, and they make recommendations that quality assurance, control, and validation practices be extended to the sampling and sample processing steps. This article will help yield more meaningful and higher quality results for decision-making regulatory and agrochemical/food industry.

Technical Abstract: Proper sampling and sample processing in pesticide residue analysis of food and soil has always been essential to obtain accurate results, but the subject is becoming a greater concern as approximately 100 mg test portions are being analyzed with automated high-throughput analytical methods by agrochemical industry and contract laboratories. As global food trade and importance of monitoring increase, the food industry and regulatory laboratories are also considering miniaturized high-throughput methods. In conjunction with a summary of the symposium, “Residues in Food and Feed - Going from Macro to Micro: The Future of Sample Processing in Residue Analytical Methods” held at the 13th IUPAC International Congress of Pesticide Chemistry, this is an opportune time to review sampling theory and sample processing for pesticide residue analysis. If collected samples and test portions do not adequately represent the actual lot from which they came and provide meaningful results, then all costs, time, and efforts involved in implementing programs using sophisticated analytical instruments and techniques are wasted, and can actually yield misleading results. This article is designed to briefly review the often-neglected but crucial topic of sample collection and processing, and put the issue into perspective for the future of pesticide residue analysis. We emphasize that analysts should demonstrate the validity of their sample processing approaches for the analytes/matrices of interest, and we encourage further studies on sampling and sample reduction to produce a test portion.