Determination of nitroxynil in cow milk by reversed-phase high-performance liquid chromatography with dual-electrode coulometric detection

• Published in: Journal of Chromatography A 1992-04, Vol.596 (1), p.67-71
• Main Authors: Takeba, Kazue, Matsumoto, Masao, Nakazawa, Hiroyuki
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; determination; Food industries; Fundamental and applied biological sciences. Psychology; high performance liquid chromatography; milk; Milk and cheese industries. Ice creams; nitroxinil; residues
• ISSN: 0021-9673
• DOI: 10.1016/0021-9673(92)80203-7

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°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 μg/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.