A gas-liquid chromatographic (GLC) method is described for the determination of diethylstilbestrol (DES) and its glucuronide (DES-G) in cattle tissues. Muscle, liver, and kidney samples are extracted with methanol and centrifuged. An aliquot of extract equivalent to 50 g tissue is evaporated to remove methanol and hydrolyzed overnight, using β-glucuronidase. In the resulting sample, free DES is purified by alkaline liquid-liquid extraction and is reacted in base with dichloroacetyl chloride to form the DES diester. The diester is measured by GLC, using a 5% UC W-98 column and electron affinity detection. Fat samples are assayed for free DES by extracting with chloroform and processing as other tissues, beginning with the alkaline purification. Residues from tissues of steers fed DES, assayed by both GLC and bioassay procedures, showed excellent agreement. In these studies the GLC procedure had a sensitivity of about 0.001 ppm. Lean and fat contained no DES residue when animals were slaughtered at 0 time off medicated feed. Liver and kidney contained residues on the order of 0.02 ppm at 0 time. The DES declined to nondetectable levels in liver and kidney by 96 hr after withdrawal. The assay procedure has been used successfully on a routine basis for several months.
An analytical method for determining residues of the fungicide tricyclazole (5-methyl-l,2,4-triazolo-[3,4-b]benzothiazole) and the major metabolite (l,2,4-triazolo[3,4-6]benzothiazole-5-methanol) in rough rice, grain components, and straw has been developed with flame photometric-gas chromatographic detection. Rice plants were foliar sprayed with tricyclazole at booting growth stage with a single 0.5 lb/A application or dual applications of 0.25 lb/A at booting and early heading growth stages. Maximum tricyclazole residues found in rough rice and straw were 3.9 and 3.5 ppm, respectively. Maximum metabolite residues found in rough rice and straw were 1.1 and 10.2 ppm, respectively. The limit of detection for tricyclazole or the alcohol metabolite in rough rice was 0.02 ppm based on a 25.0-g sample. Recoveries at the 0.10 ppm fortification level were approximately 77% for tricyclazole and 57% for the metabolite. The alcohol metabolite was derivatized and chromatographed as the trimethylsilyl (Me3Si) ether.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.