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Taking the Fat Out: Improved Sample Preparation Techniques for Toxicologic Testing of Postmortem Liver Tissue by GC-MS in Veterinary Diagnostics


An efficient and effective method for the detection of a wide variety of toxicants in liver tissue was developed and validated using gas chromatography-mass spectrometry (GC-MS). The aim of this research was to address the need for non-targeted analysis in postmortem liver samples. We wanted to find a faster, less labor-intensive method for fat removal from liver. A variety of clean-up sorbents and cartridges were assessed for their efficacy in lipid removal from liver tissue as well as analyte recovery. The study focused on the evaluation of QuEChERS solvent extraction with Enhanced Matrix Removal-Lipid (EMR-Lipid™) clean-up to remove lipids from liver tissue samples. Qualitative analysis was performed on 15 representative pesticides and 2 drugs commonly analyzed for in veterinary diagnostics. Increased sensitivity was achieved by using 5 μL injections into the GC-MS running on solvent vent mode. Probability of detection (POD) was used as the statistical model for method evaluation and validation. Three sources of liver (bovine, chicken, and caprine), with varying amounts of fat present, were tested. The QuEChERS extraction with EMR-Lipid clean-up was found to be as effective as gel permeation chromatography (GPC) in removing fats from liver tissue with minimal analyte loss. GPC, the typical clean-up method for fatty tissue samples, was the reference method used for comparison. It was determined by the POD model that the candidate method had better detection than GPC at 5 μg/g for all the analytes investigated and that the difference was statistically significant at 5 μg/g but not below that. In addition, EMR-Lipid uses substantially less solvent and is twice as fast compared to GPC.

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