Cr. White et al., OPTIMIZATION OF A LIQUID-CHROMATOGRAPHIC METHOD FOR DETERMINATION OF OXYTETRACYCLINE, TETRACYCLINE, AND CHLORTETRACYCLINE IN MILK, Journal of AOAC International, 76(3), 1993, pp. 549-554
A liquid chromatographic (LC) method was developed for the simultaneou
s identification and quantitation of oxytetracycline, tetracycline, an
d chlortetracycline in milk. Milk samples (5 mL) were deproteinized by
adding 1 mL 1N HCl and 24 mL acetonitrile, and filtering. Dichloromet
hane and hexane were added to 15 mL filtrate to separate the water lay
er. The organic layer was washed with 1 mL deionized water, and the co
mbined water layers were diluted to 4 mL. Sample aliquots of 1000 muL
were then injected directly and analyzed on an LC system. The sensitiv
ity limit of the method is 5 ppb for each antibiotic; no interferences
are present at their retention times. Mean recoveries from milk spike
d at 0.01-1 ppm ranged from 87 to 99%, and precision was good.