Search

A liquid chromatographic (LC) method is described for the quantitative determination of semduramicin sodium in broiler liver when administered under projected use conditions. For this procedure, semduramicin sodium is extracted from liver with methanolic ammonium hydroxide, separated and concentrated by solid-phase extraction steps, and determined by LC with postcolumn derivatization with vanillin. The mean recovery of drug was 95% over the 40-320 ng/g range, the coefficient of variation was +/- 10% or better, and no interference was observed from commercial polyether ionophores. The minimum level of detection for semduramicin sodium in broiler liver is 25 ng/g.

A specific assay is described for the confirmatory identification of danofloxacin residues in edible tissues of cattle and chicken. The assay utilizes on-line microbore high-performance liquid chromatography and pneumatically assisted electrospray tandem mass spectrometry (MS/MS). Collision-induced dissociation of the danofloxacin protonated molecule results in two significant daughter ions. Monitoring both ions provides the specificity required for this confirmatory assay. Optimum electrospray and MS/MS operating conditions permitted the specific monitoring of danofloxacin and the confirmation of its residues in chicken and cattle liver extracts down to 50 ppb. The analysis of control liver or the commercially available antibacterial quinolones enrofloxacin and its metabolite ciprofloxacin gave no response under the assay conditions. The ratios of the two daughter ions were similar for danofloxacin standard solutions, fortified tissues and incurred tissues.

The ion trap detector (ITD), in combination with a capillary gas chromatograph and under chemical ionization conditions, offers sufficient sensitivity to determine carbadox-related residues as the methyl ester derivative of quinoxaline-2-carboxylic acid at 3 micrograms/kg or higher in porcine liver. A tetradeuterated internal standard of QME effectively compensates for losses incurred during sample preparation. The method produced mean levels of 3.3 (+/- 0.5), 5.5 (+/- 0.8), and 10.1 (+/- 0.9) micrograms/kg for liver fortified at 3, 5, and 10 micrograms/kg. When applied to analysis of samples containing incurred residues of 14C-carbadox at the low microgram/kg level, results were comparable to those obtained by reverse isotope dilution analysis.

A gas chromatographic-mass spectrometric method with selected ion monitoring (GC/MS-SIM) is described for identification of pyrantel- and morantel-related residues in swine and beef liver. Alkaline hydrolysis of tissue liberates and converts pyrantel- and morantel-related residues to 3-(2-thienyl)-acrylic acid (TAA) and 3-(3-methyl-2-thienyl)-acrylic acid (MTAA), respectively. These thienyl acrylic acids are recovered by ion exclusion chromatography and converted to methyl ester derivatives (TAAE and MTAAE) for identification by GC/MS-SIM. When the relative intensities of the molecular ion, the base peak, and a third significant ion of the sample correspond to ion intensities of the preformed or processed standards, the identity of the residue is confirmed. The method was validated by analysis of swine and beef liver samples containing incurred residues of pyrantel and morantel under withdrawal conditions.

A gas-liquid chromatographic assay has been developed to determine major residues of morantel in bovine liver, a target tissue, at levels of 0.2-0.8 ppm. The method is based on hydrolysis of the N-methyltetrahydropyrimidine portion of morantel and its metabolites to N-methyl-1,3-propanediamine, and conversion of the diamine to an N,N'-bis-(2-nitro-4-trifluoromethylphenyl) derivative. The addition of an internal standard, N-ethyl-1,3-propanediamine, to the tissue 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-liquid chromatography over a linear dynamic range equivalent to 0.2-0.8 ppm morantel. The method has been evaluated at 0, 0.2, 0.4, and 0.8 ppm levels in fortified bovine liver, and in a withdrawal sample containing physiologically incurred morantel residues. Mean values of 0.22 +/- 0.015, 0.40 +/- 0.033, and 0.79 +/- ppm were found for fortified samples, 0.02 ppm for control liver, and 0.56 +/- 0.050 ppm for the withdrawal sample.