Determination of morantel-related residues in bovine milk by electron capture gas chromatography.
A gas chromatographic assay was developed to determine major residues of morantel in bovine milk over a range that is suitable for monitoring residues of the drug. The method is based on hydrolysis of the N-methyl-tetrahydropyrimidine portion of morantel and its metabolites to N-methyl-1,3-propanediamine, and converting the diamine to an N,N-bis-(2-nitro-4-trifluoromethylphenyl) derivative. The addition of an internal standard, the N-desmethyl-N-ethyl homolog of pyrantel, to the milk sample circumvents any potential problem that could arise from variable reaction yields, and eliminates the true recovery as a factor affecting the accuracy and precision of the procedure. The concentrations of the derivatives are determined by pulsed electron capture gas chromatography over a linear dynamic range that is equivalent to 12.5-50 ppb morantel. The method was evaluated at the 0, 12.5, 25, and 50 ppb levels in fortified bovine milk, and in a withdrawal sample containing physiologically incurred morantel residues. Mean values of 14 +/- 1.7, 24 +/- 3.7, and 47 +/- 6.9 were found for the fortified samples, approximately 3 ppb for control milk, and 16 +/- 1.7 ppb for the withdrawal sample.
D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D006868:Hydrolysis; D007202:Indicators and Reagents; D008892:Milk / Q000032:analysis*; D009015:Morantel / Q000032:analysis*; D011743:Pyrimidines / Q000032:analysis*
D007202:Indicators and Reagents; D011743:Pyrimidines; D009015:Morantel