Residue methodology for AMDRO fire ant insecticide (AC 217,300) in pasture grass and crops.

Residue methodology is described for the determination of AC 217,300 residues in pasture grass and crop samples. After extraction and subsequent cleanup on an XAD-2 column, residues of AC 217,300 are determined by liquid chromatography (LC), using a reverse phase paired-ion chromatographic system and detection at 300 nm. The method has a validated limit of sensitivity of 0.05 ppm with corresponding control values for the commodities analyzed of less than 0.01 ppm. Apparent residues over 0.05 ppm can be confirmed by either gas chromatography with an electron capture detector (GC-EC) or gas chromatography-negative ion chemical ionization mass spectrometry (GC-NICI). The direct GC-NICI method circumvents the need for sample cleanup on the XAD-2 column, and offers a greatly simplified procedure that is useful for screening samples. Recoveries of AC 217,300 from the commodities analyzed have been satisfactory with all methods of analysis.

Anthelmintic efficacy, safety, and residue evaluation of levamisole gel formulation in cattle.

Anthelmintic efficacy, safety, and residue studies were conducted in beef calves using a levamisole gel formulation. The effectiveness of levamisole gel and tablet formulations was studied in 30 calves with experimental infection of Ostertagia ostertagi. Removal of 33- to 34-day-old O ostertagi was 99.6% and 97.7%, for the gel and tablet formulation, respectively, when administered orally to supply 8 mg of levamisole HCl equivalent/kg of body weight. A comparative blood concentration study was also used to demonstrate bioequivalence of the levamisole gel to the tablet formulation. In a cross-over-designed test, 5 cattle/treatment group were dosed orally with levamisole 11.5% gel or levamisole tablets at the dosage rate of 8 mg of levamisole HCl/kg. Blood levamisole values were similar with the levamisole gel and tablet formulations. In a safety study, 3 groups of 6 calves each were given levamisole gel orally to provide 8, 24, or 40 mg of levamisole HCl/kg. A 4th group served as controls. Adverse clinical signs were not observed in cattle treated with the recommended dosage level of 8 mg/kg. Transient salivation was noticed in 1 placebo control calf, 2 calves given 24 mg/kg, and 4 calves given 40 mg/kg. Edible tissues from cattle given a single oral dose of levamisole gel (8 mg/kg) were analyzed for drug residues 2 hours and 2, 3, 5, and 7 days after treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Confirmatory method for sulfamethazine residues in cattle and swine tissues, using gas chromatography--chemical ionization mass spectrometry.

A gas chromatographic (GC) method has been reported for the determination of sulfamethazine residues in cattle and swine tissues. The extracts from this procedure were found to be directly amenable to examination by gas chromatography-mass spectrometry (GC-MS), allowing positive confirmation of an apparent residue of sulfamethazine. Chemical ionization mass spectrometry (CIMS) was chosen as the MS technique because it generated an ion indicative of intact sulfamethazine and fragment ions indicative of the amine functionality and sulfanil moiety. Positive ion (PI) chemical ionization mass spectrometry was adequate by itself for a confirmatory technique. Negative ion (NI) chemical ionization mass spectrometry alone could not be used for the confirmatory analysis of sulfamethazine, but it did offer a means to check the quantitative data from the positive ion analyses and provided complementary confirmatory data. Satisfactory recoveries were obtained for sulfamethazine in swine and cattle tissues at the tolerance level of 0.1 ppm. Apparent sulfamethazine residues in control tissues were less than 0.01 ppm.

Gas-liquid chromatographic determination of sulfamethazine in swine and cattle tissues.

A gas-liquid chromatographic (GLC) method is described for determining sulfonamide residues in animal tissues, with specificity for 7 sulfonamides. Residues are extracted from tissues with acetone-chloroform, fatty substances are removed, and the sulfonamide residue is methylated with diazomethane in acetone-ether to render it amenable to determination by gas-liquid chromatography on an all-glass column suitable for direct on-column injection and a Ni electron-capture detector. Quantitation is achieved by external standardization. The method has a validated limit of sensitivity of 0.10 ppm with the corresponding control values for all tissues being less than 0.01 ppm. Satisfactory recoveries have been obtained for sulfamethazine in swine and cattle tissues. Specificity for sulfamethazine in the presence of sulfathiazole, sulfaquinoxaline, sulfadimethoxine, sulfabromomethazine, sulfaethoxypyridazine, and sulfachloropyrazine is attained by resolution of the respective methyl derivatives on the GLC column.