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United States Department of Agriculture

Agricultural Research Service


Location: Residue Chemistry and Predictive Microbiology Research

2011 Annual Report

1a. Objectives (from AD-416)
1. Develop methods to increase sample throughput in order to improve monitoring of chemical contaminants in foods. Specifically: investigate faster screening and/or analytical approaches, and faster data processing without loss of reliability. 1A. Develop and evaluate new, useful analytical multiresidue methods that are faster than existing methods without sacrificing quality of results. 1B. Investigate practical means of processing analytical results in multiresidue analysis that lead to reliable, objective decisions with minimal human review. 1C. Develop and evaluate improved analytical screening methods in the analysis of chemicals of interest in foods. 1D. Study and implement robotic sample preparation systems to increase speed and reduce manual labor for routine analysis of chemical residues in foods. 2. Conduct research to evaluate the validity of new approaches for regulatory monitoring of veterinary drug residues in foods and feeds. Specifically: an assessment of sampling procedures and addressing matrix effects in quantification. 2A. Lead and conduct an AOAC International Collaborative Study to update and harmonize the QuEChERS method for analysis of chemical residues in a wide variety of foods. 2B. Investigate sampling and sample processing of appropriate matrices, taking matrix effects into account, for veterinary drug residue analysis to yield meaningful results in a fast and practical procedure. 2C. Lead and conduct an interlaboratory validation study to quantitatively and qualitatively assess our multiclass, multiresidue method for veterinary drugs in food tissue matrices. 3. Develop biosensor methods with multi-analyte capability for biological toxins of concern. 4. Modify/refine novel method for routine measurement of total phenolics, phytoestrogens and/or estrogenic endocrine disruptors. 4A. Expand application of our total phenolics method to other food and dietary products; and identify the reaction products of the key reagent with select phenolic compounds. 4B. Modify the method to screen for estrogenic compounds, including bisphenol A. 5. Develop novel analytical methods for inorganic and organometallic heavy metals (for example forms of mercury (Hg) and arsenic (As)) in foods and supplements. 5A. Develop modern analytical methods for mercury speciation and quantification in foods and supplements. 5B. Develop modern analytical methods for arsenic speciation and quantification in foods and supplements.

1b. Approach (from AD-416)
1a) Evaluate novel mass spectrometric methods such as ambient mass spectrometry and supersonic molecular beam mass spectrometry combined with fast gas chromatography; 1b) use robotic systems to develop fast, automated sample cleanup approaches for routine monitoring purposes; 1c) devise data handling software that is faster and better at compiling the needed information for validating multi-class, multiresidue methods for analysis; 2a) multi-laboratory AOAC International collaborative studies will be pursued to achieve the gold standard quality in method validation; 2b) both gas chromatography and liquid chromatography (LC) combined with tandem mass spectrometry (MS/MS) will be used to assess and address matrix effects in chemical residue analysis of foods; 3) surface plasmon resonance biosensing instrumentation and techniques will be used to develop advanced new methods for multiple toxins of concern; 4) both LC-MS/MS and novel, quick chemical test methods will be used to measure total phenolics, phytoestrogens and endocrine disruptors; and 5) LC combined with atomic fluorescence spectroscopy will be used to rapidly and accurately determine different organometallic species of Hg and As in foods and supplements.

3. Progress Report
This project addresses the problem related to the lack of rapid, automated, cost-effective, waste-minimizing, safe, and high-quality analytical methods to detect multiple chemical residues and other toxic compounds in foods. The project is devised to meet the needs of the USDA Food Safety Inspection Service (FSIS), Food and Drug Administration (FDA), and other organizations that monitor chemical residues in food, which also includes industry, consumer groups, and academic scientists. This new Project Plan proposal completed the review process and was established on Jan. 19, 2011. In July of 2011, we were able to hire a Research Chemist to fill the vacant position in the Residue Chemistry group to work on Objectives Milestones 1A and 2A. Progress on those first-year milestones was delayed until the new scientist could be hired. At the end of 2010, a Biologist left the group to take another job. The vacancy has been converted to a Technician position that should be filled by October, 2011. With respect to Objective/Milestone 2B, we have completed the method development, laboratory validation, and technology transfer activity of the first phase of the multi-class, multi-residue monitoring method for >60 high priority veterinary drugs in beef kidney and muscle. We are in the process of adding more drug analytes and matrices (e.g. pork) to further increase scope of the monitoring scheme. FSIS has approved and implemented the initial method, and we continue to work together with FSIS to most efficiently meet their needs. We similarly worked closely with FSIS to meet their needs on the first-year Objective/Milestone 3 to complete the development of latex agglutination assays for the “top six” non-O157 STEC (shiga-toxin producing E. coli) that have caused outbreaks and illness as severe as by O157:H7. A collaboration with a Visiting Scientist from China was established for a year staring in June of 2011 to contribute to Objectives/Milestones 3 and 4 of the Project Plan. Further progress was made on Objective/Milestone 4A on the evaluation of the total phenolics method to additional food products. Due to a year delay in the purchase of the atomic fluorescence instrument for Objective/Milestone 5, those investigations had to be pushed back. Instead, development of a field-based screening instrument continued and the ARS patent committee approved the pursuit of a patent for a spectroscopic device to detect illegal dyes in seafood.

4. Accomplishments
1. Development, validation, and technology transfer of multiclass, multiresidue method for veterinary drugs in animal tissues. Currently, the USDA Food Safety Inspection Service (FSIS) uses a 7-plate microbial growth inhibition assay to screen for antimicrobial drug residues in beef samples from slaughter establishments throughout the U.S. Drawbacks include that it takes 24 hours to yield a result, the responses do not identify the drug (only the antibiotic class), and it is unable to detect many common drugs of regulatory interest. ARS researchers at Wyndmoor, PA, developed, validated, and transferred to FSIS an improved screening method that also can identify individual drug residues in the samples. The method targets 60 of the most important drugs of regulatory concern and is able to screen at concentrations below regulatory tolerance levels. A single analyst can perform sample preparation of 60 samples with the method in an 8-hour day for a series of sequential 10 minute analyses. Implementation of the method in the USDA-FSIS National Residue Program will serve to improve the monitoring and enforcement of veterinary drug residues, and thereby assure better animal husbandry practices, reduce environmental contamination, decrease microbial antibiotic resistance, and increase food safety.

2. Development, evaluation, and transfer of latex agglutination tests (LATs) for detection and confirmation of six pathogenic non-O157 Escherichia Coli. Current testing methods tend to look only for O157:H7 bacteria, but shiga-like toxins can occur in additional strains to cause major food safety problems. Better testing methods are needed for shiga-like toxins to better protect the food supply and consumer. Rapid LATs were developed by ARS researchers at Wyndmoor, PA, for E. coli O26, O45, O103, O111, O121 and O145, and the assays were tested in ERRC against 38 E. coli strains and FSIS tested 74 strains. After successfully conducting 3 trials each on 3 batches of the LATs, the reagents and test protocol were transferred to FSIS. FSIS tested these reagents in 67 E. coli strains and 7 non-E. coli bacterial strains. These LATs are being utilized by FSIS for monitoring, and FSIS will further transfer to industry the technology of manufacturing the kits for future monitoring.

3. Development of improved qualitative and quantitative methods for microcystins (MCs) in fish. MCs are the most common cyanotoxins found world-wide in freshwater, brackish and marine environments. The rapid and accurate analysis of MCs and nodularin (Nod-R) in fish tissue is important for determining occurrence, following trends, and monitoring exposure for risk assessment, and other purposes. In this work, ARS researchers in Wyndmoor, PA, developed a streamlined and reliable sample preparation method for 8 MCs and Nod-R in fish, and conducted a validation of the new method using liquid chromatography – tandem mass spectrometry for identification and quantitative analysis. For additional confirmation, we used a commercial enzyme-linked immunosorbent assay kit. Detection limits were <10 ng/g in the fish tissue (catfish, basa, and swai filets), and no false positives or false negatives occurred in blind analyses of many spiked samples. This method is thought to be the best currently available, and ready for use in monitoring studies. The protocol was transferred to the Food Emergency Response Network for implementation in case of an MC outbreak in fish.

4. Faster analysis of pesticides in foods. It is always desirable to use faster and better methods of analysis to monitor pesticide residues in foods. ARS researchers at Wyndmoor, PA, validated both qualitatively and quantitatively the updated QuEChERS (quick, easy, cheap, effective, rugged, safe) version coupled to low-pressure gas chromatography-tandem mass spectrometry for fast analysis of 150 pesticides in cantaloupe, broccoli, lemon, sweet potato, and catfish. The enhanced selectivity and sensitivity of this approach allowed the 150 pesticides to be separated in <7 minutes and to achieve <5 ng/g limits of quantification for nearly all pesticides. Qualitatively, no false positives or false negatives were observed for 100 randomly spiked extracts at >10 ng/g in the different matrices, which were analyzed in blind fashion. This is a state-of-the-art method for pesticide residue analysis that will be studied in an AOAC International collaborative study for enhanced technology transfer of the method to monitoring laboratories around the world.

Review Publications
Lehotay, S.J., Koesukwiwat, U., Van Der Kamp, H., Mol, H.G., Leepipatpiboon, N. 2011. Qualitative aspects in the analysis of pesticide residues in fruits and vegetables using fast, low-pressure gas chromatography - time-of-flight mass spectrometry. Journal of Agricultural and Food Chemistry. 59:7544-7556.

Last Modified: 05/26/2017
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