IMPROVED LIQUID-CHROMATOGRAPHIC DETERMINATION OF NEOMYCIN-B IN BOVINEKIDNEY

An improved liquid chromatographic (LC) method was developed for the d etermination of neomycin B in bovine kidney tissue. The tissue is homo genized twice in phosphate buffer; homogenate is centrifuged, and the supernatant is deproteinated by heat. The extract is acidified and mix ed with ion-pair concentrate, and neomycin B is determined by an LC sy stem consisting of an ion-pairing mobile phase, a reversed-phase ODS c olumn, postcolumn derivatization with o-phthalaldehyde reagent, and fl uorometric detection. Average recoveries of neomycin B from kidney tis sues spiked at 3, 6, and 12 ppm were 103, 99, and 104%, with 9.7, 7.9, and 3.7% intralaboratory coefficients of variation, respectively, usi ng a standard curve prepared in buffer. The method was used to determi ne neomycin B in kidney tissue obtained from a calf killed 14 days aft er intramuscular dosing with neomycin (5 mg/lb). The tissue was found to contain about 3 ppm neomycin B. The LC conditions were also used to assay control samples of muscle, liver, milk, plasma, and urine. No i nterfering peaks were noted at the elution position of neomycin B.