Determination of nitroxynil in cow milk by reversed-phase high-performance liquid chromatography with dual-electrode coulometric detection.
A sensitive and specific method is described for the determination of nitroxynil (fasciolicide) residues in cow milk. The milk samples were extracted with acetone and acetonitrile, following clean-up using a simple liquid-liquid extraction step. Nitroxynil was separated from the matrix peaks by reversed-phase high-performance liquid chromatography and detected using dual-electrode coulometric detection. The mobile phase was a mixture (20:80, v/v) of acetonitrile and 0.05 M potassium dihydrogenphosphate with the pH adjusted to 4.0. The flow-rate was 1 ml/min at 40 degrees C. The applied potentials of detectors 1 and 2 were maintained at -0.7 and +0.2 V, respectively. Average recoveries (n = 5) of nitroxynil from milk samples spiked at concentrations of 0.01 and 0.1 micrograms/ml were found to be 92.0% and 97.0% with coefficients of variation of 6.2% and 2.2%, respectively. The detection limit of nitroxynil in milk was 0.7 ng/ml. During the analysis of 30 raw cow milk and 140 market milk samples, nitroxynil was detected at a level of 4 ng/ml in one raw cow milk sample.
Takeba
K
K
Department of Food Hygiene and Nutrition, Tokyo Metropolitan Research Laboratory of Public Health, Japan.
Matsumoto
M
M
Nakazawa
H
H
D000818:Animals; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000032:analysis*; D009611:Nitroxinil / Q000032:analysis*
D009611:Nitroxinil