Determination of pirlimycin residue in milk by liquid chromatographic analysis of the 9-fluorenylmethyl chloroformate derivative.
A procedure to determine pirlimycin residues in bovine milk was developed. Pirlimycin was extracted from milk after protein precipitation and 2 stages of liquid-liquid partitioning. The extract was evaporated to dryness, redissolved in dilute base, and derivatized with 9-fluorenylmethyl chloroformate (Fmoc) to impart a chromophore for ultraviolet (UV) detection. The derivatized extract was analyzed by reversed-phase liquid chromatography (LC). Pirlimycin concentration was calculated from the peak height of the extract by using a linear regression standard curve prepared from a series of derivatized standards. The procedure's performance in the range of the regulatory tolerance (0.4 ppm) was validated by replicate analysis of control, fortified control, and residue-incurred bovine milk. Average recoveries at 0.2, 0.4, and 0.8 ppm were 91, 88, and 87%, respectively, and coefficients of variation were 5, 4, and 1%, respectively. Overall recovery for all samples was 89%, with 4% coefficient of variation. Linear regression analysis of LC/UV results versus results from a previously published LC/mass spectrometric assay gave a slope of 0.95, with a correlation coefficient of 0.98.
Heller
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U.S. Food and Drug Administration, Center for Veterinary Medicine, Laurel, MD 20708, USA.
D000818:Animals; D002853:Chromatography, Liquid; D002981:Clindamycin / Q000031:analogs & derivatives* / Q000032:analysis; D004350:Drug Residues; D005449:Fluorenes; D007202:Indicators and Reagents; D016014:Linear Models; D008892:Milk / Q000737:chemistry*
D005449:Fluorenes; D007202:Indicators and Reagents; D002981:Clindamycin; C054007:1-(9-fluorenyl)methyl chloroformate; C034093:pirlimycin