IDENTIFICATION AND MEASUREMENT OF BETA-LACTAM ANTIBIOTIC RESIDUES IN MILK - INTEGRATION OF SCREENING KITS WITH LIQUID-CHROMATOGRAPHY

A procedure for identifying and quantitating violative beta-lactams in milk is described, This procedure integrates beta-lactam residue dete ction kits with the multiresidue automated liquid chromatographic (LC) cleanup method developed in our laboratory. Spiked milk was deprotein ized, extracted, and subjected to reversed-phase LC using a gradient p rogram that concentrated the beta-lactams. Amoxicillin, ampicillin, ce phapirin, ceftiofur, cloxacillin, and penicillin G were, thus, separat ed into 5 fractions that were subsequently tested for activity by usin g 4 kits, beta-lactams in the positive fractions were quantitated by a nalytical LC methods developed in our laboratory, The LC cleanup metho d separated beta-lactam antibiotics from each other and from interfere nces in the matrix and also concentrated the antibiotics, thus increas ing the sensitivity of the kits to the beta-lactam antibiotics. The pr ocedure facilitated the task of identifying and measuring the beta-lac tam antibiotics that may be present in milk samples.