Sample Processing (Comminution) and Preparation

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Webinar Date/Time: Tue, Sep 19, 2023 11:00 AM EDT

Sample processing (comminution) is often taken for granted by analytical chemists, who tend to begin the steps in analytical methods with extraction of a test portion. However, the entire analysis is a waste of time, effort, and resources if the test portion does not represent the original sample. This webcast will describe the importance of sample comminution, particularly for monitoring chemical contaminants in foods.

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Event Overview.

Like a chain is only as strong as its weakest link, both the overall accuracy and speed in the analysis of chemical contaminants in food is limited by the least accurate and slowest steps, respectively. Sample processing—comminution—of bulk samples to generate the test portion for analysis is nearly always the limiting step in both regards. Regulatory entities worldwide call for comminution of 1 kg bulk samples for most food commodities in pesticide residue monitoring, which requires large food processors. Several studies have demonstrated that cryogenic comminution with liquid nitrogen or dry ice leads to best performance, but until now, no devices had yet been commercialized to accommodate such large watery samples.

In this study, a new device was evaluated for QuEChERSER sample preparation. Both GC-MS/MS and LC-MS/MS analysis of many pesticides, environmental contaminants, veterinary drugs, and mycotoxins in 1 kg samples of watermelon, grapes, green beans, tomatoes, avocado, grains, and kidney/liver were processed using liquid nitrogen, dry ice, and at room temperature. Acceptable consistency was initially shown for test portions as low as 0.5 g, and full results will be presented.

Key Learning Objectives:

  • Learn about a method and device to comminute 1 kg bulk samples to yield consistently representative 1-2 g test portions in a single step for streamlined sample preparation and analysis.
  • Learn about the “quick, easy, cheap, effective, rugged, safe, efficient, and robust” (QuEChERSER) mega-method for analysis of a wide range of analytes and foods.
  • Understand the effect of cryogenic bulk sample processing to reduce analyte degradation and volatilization while improving reproducibility even with small test portions.

Who Should Attend:

  • Any chemist, technician, or lab manager interested in sample processing (comminution) in analytical chemistry, particularly for food analysis.


Steven Lehotay
Lead Scientist

Steven J. Lehotay is a Lead Scientist with the USDA Agricultural Research Service at the Eastern Regional Research Center in Wyndmoor, Pennsylvania (near Philadelphia). Since 1992, he has conducted scientific investigations and method development research involving improvement in the analysis of pesticides, veterinary drugs, and other contaminants in food. His work with many partners has addressed all aspects of the analytical process using many different techniques applied in novel and useful ways. Steve has been honored with numerous awards. Within the USDA, that includes a Secretary’s Honor Award, the Early Career, Distinguished, and Senior Research Scientist of the Year Awards, and two Technology Transfer Awards. He’s also a recipient of an AOAC International Harvey W. Wiley Award, ACS-AGRO Innovation in Chemistry of Agriculture Award, NACRW Excellence and Founders Awards, The Analytical Scientist Power List Top 10 Public Defender, and Clarivate Analytics Highly Cited Researcher. According to the Stanford c-score metric, Steve ranks among the top 0.14% of published analytical chemists.

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