Wa. Moats et R. Harikkhan, RAPID HPLC DETERMINATION OF TETRACYCLINE ANTIBIOTICS IN MILK, Journal of agricultural and food chemistry, 43(4), 1995, pp. 931-934
A previously described method using on-line concentration and gradient
elution was modified for more rapid isocratic analysis. Milk (5 mL) w
as extracted/deproteinized with 1 mL of 1 N HCl and 15 mL of acetonitr
ile. The resulting filtrate (12 mL) was evaporated directly, or the wa
ter layer resulting from addition of hexane and methylene chloride was
evaporated. The extract could be concentrated to about 1 mL without s
ignificant degradation of tetracyclines. The concentrates were filtere
d. For analysis, a Polymer Laboratories PLRP-S column was used with a
mobile phase of 0.02 M H3PO4 and 0.01 M sodium decanesulfonate-acetoni
trile, 72 + 28 for oxytetracycline and tetracycline and 68 + 32 for ch
lortetracycline. The injection volume was 200 mu L with UV detection a
t 380 nm. Average recoveries were greater than 80% with detection limi
ts of 2-4 ppb.