Liquid chromatographic determination and identification of morantel-related residues as precursors of 3-(3-methyl-2-thienyl) acrylic acid (CP-20,107) in bovine milk.
A simple liquid chromatographic (LC) method was developed to determine and identify incurred morantel-related residues in bovine milk by converting them to 3-(3-methyl-2-thienyl) acrylic acid (CP-20, 107). Key techniques in this method involve short-term digestion of milk in HCl to release residues convertible to CP-20, 107, isolation and alkaline hydrolysis of these precursors to CP-20, 107, and recovery of the product for LC analysis. Photochemical conversion of CP-20, 107 to its cis-isomer and separation by LC identifies the residue. A homolog (pyrantel), which is used as an internal standard, is hydrolyzed to 3-(2-thienyl) acrylic acid. These acrylic acid isomers are readily resolved by LC. The method was evaluated over the 1-4 ppb (ng/mL) range for accuracy and precision to assess its utility for withdrawal studies. Bovine milk supplemented with morantel at 1, 2, and 4 ppb and assayed in replicate (n = 7-8) over 4 trials gave mean values and standard deviations of 1.0 +/- 0.11, 2.0 +/- 0.24, and 4.0 +/- 0.44 ppb, respectively. A milk specimen containing physiologically incurred residues of morantel assayed 2.1 +/- 0.19 ppb in replicate (n = 5).
D000818:Animals; D002417:Cattle; D002853:Chromatography, Liquid; D006868:Hydrolysis; D007202:Indicators and Reagents; D008892:Milk / Q000032:analysis*; D009015:Morantel / Q000031:analogs & derivatives / Q000032:analysis*; D011715:Pyrantel / Q000032:analysis; D011743:Pyrimidines / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D013876:Thiophenes / Q000032:analysis*
D007202:Indicators and Reagents; D011743:Pyrimidines; D013876:Thiophenes; D011715:Pyrantel; C050478:3-(3-methyl-2-thienyl)acrylic acid; D009015:Morantel