Submitted to: Drug Testing and Analysis Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/13/2012
Publication Date: 8/1/2012
Citation: Schneider, M.J., Lehotay, S.J., Lightfield, A.R. 2012. Evaluation of a multiclass, multiresidue liquid chromatography-tandem mass spectrometry method for analysis of 120 veterinary drugs in bovine kidney. Drug Testing and Analysis Journal. 4(1):91-102. Interpretive Summary: Use of veterinary drugs in animals used for food requires monitoring of the food supply to ensure that any drug residues present are at levels below the tolerance set by the U.S. Food and Drug Administration. Monitoring methods have traditionally been designed for single drugs, or for multiple drugs belonging to the same class. Methods which allow for simultaneous monitoring of multiple drug residues from multiple classes can provide increased efficiency. In this work, such a multiclass multiresidue method was optimized and validated in kidney for use in the monitoring process. Control kidney samples were fortified at 10, 50, 100, and 200 ng/g with a mixture of 120 veterinary drugs. After extraction of these samples, recoveries of drugs, precision, and lowest calibration levels for each drug were reported. The method was judged to be successful for a majority of the drugs tested, and serves as an efficient and useful additional option for monitoring veterinary drug residues in food.
Technical Abstract: Traditionally, regulatory monitoring of veterinary drug residues in food animal tissues involves the use of several single-class methods to cover a wide analytical scope. Multiclass, multiresidue methods of analysis tend to provide greater overall laboratory efficiency than the use of multiple methods, and liquid chromatography – tandem mass spectrometry (LC-MS/MS) of targeted drug analytes usually provides exceptional performance even for complicated sample extracts. In this work, a LC-MS/MS method was optimized and validated in a test of 120 drug analytes from 11 different classes in bovine kidney. The method used 10 mL of 4/1 acetonitrile/water for extraction of 2 g samples and cleanup with hexane partitioning. Quantitative and qualitative performance was assessed for the analytes at fortification levels of 10, 50, 100, and 200 ng/g. With the method, 66 drugs gave 70-120% recovery with is less than or equal to 20% RSD at all levels over the course of 3 days. For levels is greater than or equal to50 ng/g, 72 drugs met these same standards. Limits of detection were is less than or equal to 10 ng/g for 109 of the analytes in the kidney matrix in validation experiments. Qualitatively, MS/MS identification criteria were set that ion ratios occur within +/10% (absolute value) from those of the analyte reference standards. At the 10 ng/g level, 57% of the drugs met the identification criteria, which improved to 84% at the 200 ng/g level. The method serves as an efficient and useful additional option among the current monitoring methods available.