SPECTROPHOTOMETRIC DETERMINATION OF ETHIOFENCARB IN WATERS BY REACTION WITH P-AMINOPHENOL

An automatized procedure has been developed for the spectrophotometric determination of ethiofencarb in water by reaction with p-aminophenol after alkaline hydrolysis to obtain the corresponding phenol sulphone . The hydrolyzed samples are continuously introduced into different ma nifolds at the same time as 300 mg/l p-aminophenol, 0.004 mol/l KIO4 a nd 0.04 mol/l NaOH solutions. The absorbance is measured at 638 nm aft er a reaction time of 6 min in stop flow. This absorbance band corresp onds to the indo dye obtained from the reaction between the phenol sul phone of ethiofencarb and the quinoneimine form of the p-aminophenol a nd it permits a matrix-free spectrophotometric determination of ethiof encarb with a limit of detection of 33 mug/l. The recovery of ethiofen carb in different water matrices varies from 71 to 126%.