The c ~s -[ R u ~~( L ) ~( O H ~) ~] ~+complexes (L = substituted 2,2'-bipyridines or 1 ,lo-phenanthrolines, catalyse oxidation of saturated hydrocarbons to alcohols and ketones by t-butyl hydroperoxide; the low values of kinetic isotope effect ( k ~l k ~ = 3.5 for cyclohexane) and tertiary to secondary C-H bond relative reactivities (ktertlksec ca. 6.5 for adamantane) are in a range expected for hydrogen atom abstraction by radical species.

No abstract

A sensitive and selective LC-FLD method was described for determination of closantel and rafoxanide in bovine and ovine muscles. Bovine and ovine muscles were extracted with ACN and acetone mixture (80:20, v/v). After cleanup with Oasis MAX SPE cartridges, the sample was analyzed by LC-FLD using the control point approach. No false-negative result was observed at or below maximum residue limits and the false-positive rate was below 5%. Suspected positive sample was confirmed by LC-MS/MS. This method was suitable for screening of large batch of samples and hence considerably reduced the time and cost required for quantitation and confirmatory analyses.

A survey was conducted from 1993 through 1995 to monitor organochlorine pesticides and their metabolite residues in milk available in local Hong Kong markets. Of 252 samples analyzed, including pasteurized milk, fresh milk, and raw milk, 42 contained organochloride pesticide residues at levels exceeding the Extraneous Maximum Residue Limits of the Codex Committee on Pesticide Residues. DDE and HCH isomer levels were substantially higher than those found in a 1984–1987 survey, probably because the source of cow’s milk has shifted from local dairy industries to mainland China over the past decade. Although organochlorine pesticides such as DDT and HCH have been banned in China since 1983, residues of such compounds may still persist in the environment and cause contamination through the food chain.

An HPLC method with a fluorescence detector (HPLC-FLD) was described for the quantitative determination of closantel and rafoxanide in bovine and ovine muscles. A structural analog closely related to rafoxanide, viz., N-[4-(4-chlorophenoxy) phenyl]-2-hydroxy-3,5-diiodobenzamide, was synthesized as an internal standard. Bovine and ovine muscles were extracted with acetonitrileacetone (60 + 40, v/v) followed by cleanup on mixed mode anionic exchange SPE cartridges. After evaporation and reconstitution with the mobile phase, the sample was analyzed by HPLC-FLD using internal standard calibration. The method was validated by using fortified bovine and ovine muscles at 15, 30, and 60 µg/kg. The accuracy and RSD were 70110% and 10%, respectively.