An HPLC method for the determination of penicillin G residues in veal calfliver tissues

A method developed in our laboratory and used for several years for the rou tine determination of penicillin G residues in animal tissues by liquid chr omatography failed when it was used in a recent study for the determination of penicillin G residues in liver tissues of 2- to 5-week-old veal calves. The method was, therefore, modified as follows to permit the determination of penicillin G residues in liver tissues from very young calves. Penicill in G was extracted from calf liver tissue with acetonitrile instead of wate r. The acetonitrile extract was evaporated to near dryness, and the resulti ng residue was dissolved in 30 mL of 2% sodium chloride and cleaned up on a t-C-18 Sep-Pak cartridge. The retained penicillin was then eluted with 1 m L of 60% acetonitrile/35% water/5% 0.2 M phosphate buffer solution, derivat ized with 1 mL of 1,2,4-triazole/mercuric chloride solution at 65 degreesC for 30 min, and analyzed by reverse-phase liquid chromatography with ultrav iolet detection at 325 nm. The limits of detection and quantitation for thi s method are 1.5 and 5 ng/g, respectively, for penicillin G.