Tissue samples, such as bovine muscle and liver, are typically extracted with an acetonitrile based solvent for LC-MS determination of veterinary drug residues. Among the most significant co-extracted substances are fats and polar lipids, particularly phospholipids (lecithin). A gram of bovine liver typically contains about 45 mg of fat, about half the amount usually present in muscle tissue, but still significant. Bovine liver is also a very good source of dietary lecithin (phospholipids); a gram of liver contains about 25 mg of phospholipids, about four times the amount typically found in muscle. Fats can be removed from the acetonitrile based tissue extracts by liquid extraction with hexane or with SPE with octadecyl silica (C18). Although C18 is effective for removal of most non-polar lipids, it does not remove phospholipids. Excessive amounts of phospholipids can shorten LC column life, contribute to ion-suppression, and contaminate the mass-spectrometer. In this study a novel reversed-phase sorbent is used for highly effective removal of both phospholipids and fats from bovine liver extracts prior to LC-MS/MS analysis. Greater than 95 % of phospholipids and greater than 85 % of fats were effectively removed from the tissue extracts after the simple pass-through SPE procedure. Recoveries of 45 compounds with published MRLs in beef liver averaged 83% with only a few compounds under 60%.

Rapid, simple, and effective cleanup of bovine liver samples prior to UPLC-MS/MS multiresidue veterinary drugs analysis

254th National Meeting (2017)

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