[Concentration in plasma and excretion in milk of lactating cows after oral administration of tribromsalan, oxyclozanide and bromofenofos].

The fasciolicides tribromsalan (TBS), oxyclozanide (OCZ) and bromofenofos (BFF) were orally administered to three lactating cows. The concentrations of TBS, OCZ and the BFF metabolite dephosphate bromofenofos (DBFF) in plasma, and the excretion of these compounds in milk were determined by high-performance liquid chromatography. In plasma, the concentrations of TBS, OCZ and DBFF reached maximum at about 1.0 day and the compounds remained detectable until 5.7, 7.4 and 15.1 days after administration, respectively. The detection limits of these compounds in plasma were 10, 2 and 2 ppb, respectively. In milk, the concentrations of TBS, OCZ and DBFF reached maximum at about 24 hours and the compounds remained detectable until 30-47, 30-47 and 78-119 hours after administration, respectively. The detection limits of these compounds in milk were 5.1 and 1 ppb, respectively. The residence times of TBS and BFF were very close to the withdrawal times of the fasciolicides.

[Determination of levamisole in livestock products using high performance liquid chromatography].

A method is described for the determination of the anthelmintic levamisole in muscle, liver, kidney and fat of cattle, swine and poultry using high performance liquid chromatography with photodiode array detection. Levamisole was extracted from an alkaline sample with ethyl acetate and back-extracted with 0.1 mol/L hydrochloric acid. The extract was applied to an SCX solid-phase extraction column. The column was washed with water and methanol. Levamisole was eluted with a solution of ammonia in methanol. The eluate was evaporated to dryness and the residue was dissolved in the mobile phase and injected into the HPLC system. Mean recoveries from 0.01-0.10 microgram/g fortified muscle, liver, kidney and fat samples ranged from 78.3 to 99.8%. The detection limit for the assay was 0.005 microgram/g.

[Determination of benzimidazole anthelmintics in livestock foods by HPLC].

A simple and rapid liquid chromatographic method was developed for the simultaneous determination of twelve benzimidazole anthelmintics in livestock foods using reversed-phase high-performance liquid chromatography with photodiode array detection (PDA). A sample was homogenized with acetonitrile and n-hexane, and centrifuged. The acetonitrile phase was isolated and evaporated. The residue was dissolved in 0.1 mol/L carbonate buffer solution (pH = 9.1), sonicated, and then subjected to clean-up on a Bond Elut LRC-C18 cartridge. The benzimidazole compounds were separated isocratically on a Capcell Pak C18 UG 120 (5 microns, 150 x 4.6 mm i.d.) column and detected by PDA at 295 and 313 nm. Mixtures of acetonitrile and 0.05 mol/L ammonium acetate in mixing ratios of (20:80) and (40:60) were used as the mobile phase, and the flow-rate was 1.0 mL/min at 40 degrees C. The mean recoveries (n = 3) from 0.1-0.5 microgram/g added samples were 72.6-97.2% with coefficients of variation of 0.3-8.5%. The detection limits were 0.01-0.05 microgram/g.