The purification of NADP‐linked isocitrate dehydrogenase from ox heart mitochondria is described. The molecular weight from gel filtration, sedimentation equilibrium and gel electrophoresis is 90000 ± 4000, and there are two subunits in the molecule each of which binds NADPH with enhancement of the coenzyme fluorescence. The amino‐acid composition is reported, and the absorption coefficient, A2801% estimated from dry weight measurements is 11.8 cm−1.

Methods are described for the analysis of residues of the herbicide benzoylpropethyl, ethyl ( k )-2-[N-(3,4-dichlorophenyl)benzamido]propionate, and its breakdown product, (~)-2-[N-(3,4-dichlorophenyl)benzamido]propionic acid, in wheat and soil.In wheat the acid degradation product conjugates with plant sugars and the present paper includes methods for determination of these residues either separately or as a combined residue with unconjugated acid. Efficient extraction procedures have been developed together with partition and column chromatographic techniques for purification of extracts. The full analytical procedures are described and the final determinations are by g.1.c. with electron capture detection with blank values for field samples in the range 0.01-0.05 mg/kg. Good recoveries were obtained. Radiochemical techniques have been used to verify the extraction and subsequent procedures in the methods.

An analytical method for determining residues of dichlorvos with a limit of determination of 0.01 p.p.m. is described. I t is intended for use by those laboratories which carry out residue analysis for regulatory purposes, with an emphasis on speed, specificity and sensitivity.Residues of dichlorvos are extracted with either dichloromethane or ethyl acetate, the extracts are cleaned up by steam distillation and the concentration of insecticide is determined by gasliquid Chromatography in which one of three selective detectors, the flame-photometric, "thermionic" or electron-capture detector, is used.THE analysis for traces of dichlorvos (00-dimethyl-0-2,2-dchlorovinyl phosphate, DDVP, Vaponat) has been approached in several different ways. For exarqple, the determination of total organophosphorus has been carried out by Laws and Webleyl and by Saliman.2 Colorimetric analysis methods were developed by Geiger and Furer,3 with alkaline resorcinol as reagent, by hug he^,^ who used 2,4-dinitrophenylhydrazine and by Mitsui, Osaki, Kumano and S a n ~, ~ who used alkaline acetone. Sun and Johnson6s7 have taken advantage of the volatility of dichlorvos to devise a specific bioassay method. Cholinesterase inhibition procedures involving several different methods of determination of substrate have been described by Giang, Smith and Hall,* and by P ~r t e r , ~ and automated methods by Ott and Guntherlo * Method submitted for discussion t o the Commission on Residue Analysis, Pesticides Section, Applied t "Vapona" is a Shell Trade Mark.

No abstract

Trials have been carried out with “VAPONA” Pest Strips under practical conditions in houses in the U.K. and France. The purpose of these trials was to determine the residues of dichlorvos that occur in food prepared in kitchens in which strips were placed. Samples, each of which consisted of the combined food and drink for an adult for a day, were taken at intervals during the trials. The food items were exposed and the meals prepared, including any cooking, in the way normal to the household. The analyses for dichlorvos were carried out by a g.l.c. method using flame photometric detection. The results show that the residue concentrations from all the individual samples were less than 0.1 part/million. In the U.K. trial, the mean dichlorvos levels in samples taken 7, 42 and 70 days after the strips were hung were 0.03, 0.03 and 0.02 part/million respectively. In the French trial, the mean concentrations were a little lower, being 0.02, 0.02 and less than 0.01 part/million at the same times. The items of food and the way in which they were processed varied widely from sample to sample and also between the two countries. However, the residue concentration in a sample did not appear to be correlated with the food items or with the manner of processing. No relationship was observed between the volume of the kitchens used, which varied from 14 to 45 m3, and the level of residues found in the samples.