Lily C. Hsieh

Methodology for the analysis of fenbendazole and its metabolites in plasma, urine, feces and tissue homogenates

New methodology for the extraction and analysis of the anthelmintic fenbendazole and its metabolites from plasma, urine, liver homogenates, and feces from several animal species is presented. Quantitation of fenbendazole and its metabolites was conducted by high-pressure liquid chromatography using ultraviolet detection at 290 nm. The combined extraction and analysis procedures give excellent recoveries in all of the different biological matrices examined. High specificity, low limits of detection, and excellent linearity, accuracy, and inter- and intrasample variability were also obtained. The study of fenbendazole pharmacokinetics in vitro and in vivo should be greatly enhanced through the utilization of these methods.

Matrix solid phase dispersion (MSPD) extraction and liquid chromatographic determination of five benzimidazole anthelmintics in pork muscle tissue

Abstract A method for the extraction and liquid chromatographic determination of five benzimidazole anthelmintics (thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole) in pork muscle tissue is presented. Blank or benzimidazole-fortified pork muscle tissue samples were blended with octadecylsilyl (C18, 18% load, endcapped) derivatized silica packing material. A column made from this tissue/C18 blend was washed with hexane then the benzimidazoles were eluted with acetonitrile. The acetonitrile eluate was purified by passing it through an activated alumina column. The purified eluates contained the benzimidazoles and were free of interferences as determined by liquid chromatography on ODS columns. The standard curves of individual benzimidazoles isolated from fortified samples, utilizing internal standards, were linear with average relative percentage recoveries of 86, 92, 85, 93, and 98% for thiabendazole, oxfendazole, mebendazole, albendazole, and fenbendazole, respectively, over the concentration range of 100 to 3200 ng benzimidazole/g tissue. The interassay variabilities ranged from 4 to 7% and intraassay variabilities ranged from 2 to 3%.

A Multiresidue Method for the Isolation and Liquid Chromatographic Determination of Seven Sulfonamides in Infant Formula

Abstract A multiresidue method for the isolation and high performance liquid chromatographic (photodiode array, UV 270nm) determination of sulfathiazole, sulfisoxazole, sulfamerazine, sulfamethazine, sulfamethoxazole, sulfisoxazole and sulfadimethoxine in a milk-based infant formula is presented. Blank or sulfonamide spiked infant formula samples were blended with octadecylsilyl derivatized silica (C-18) packing material. A column made from the C-18/infant formula matrix was first washed with hexane following which the sulfonamides were eluted with methylene chloride. The eluate contained sulfonamide analates which were free from interfering compounds when analyzed by liquid chromatography. This resulted in correlation coefficients (0.9973 ± 0.0016 to 0.9992 ± 0.0006), recovery percentages (75.91 ± 11.12% to 112.01 ± 8.15%) and inter- (5.51 ± 1.74% to 15.27 ± 8.14%) and intra-assay (1.71 to 8.89%) variabilities for individual sulfonamides, over the concentration range (62.5 to 2000 ng/mL) examined, that a...

Characterization of the thermal decomposition products of the sulfonylurea herbicide chlorsulfuron

Abstract Gas chromatography injection port thermal decomposition of chlorsulfuron resulted in two volatile decomposition products (2-amino-4-methoxy-6-methyl-1,3,5-triazine and 2-chlorobenzenesulfonamide) which were characterized by gas chromatography and gas chromatography-mass spectrometry. Quantitation of chlorsulfuron as its volatile thermal decomposition product 2-amino-4-methoxy-6-methyl-1,3,5-triazine was accomplished by gas chromatography-nitrogen-phosphorus detection analysis and the linearity of standard curves so obtained was independent of injection volume (0.5–3 μl) and injection port temperature (230–270°C) for the concentration range examined (62.5–1000 ng/ml).