FLOW-INJECTION SPECTROPHOTOMETRIC DETERMINATION OF PROPOXUR WITH PARAAMINOPHENOL

The spectrophotometric determination of propoxur [2-(1-methylethoxy)phenyl methyl carbamate] was carried out with p-aminophenol (PAP) in a flow system. The method involves the on-line hydrolysis with NaOH of propoxur to 2-isopropoxyphenol and the oxidation of PAP to its reactive quinone imine with KIO4 and the reaction between the phenolate and the quinone imine. A four-channel flow manifold was employed to carry out all the different steps of the reaction considered, monitoring the indo dye formed at 600 nm. The developed procedure provides a typical calibration line of A = -0.000(7) + 1.8 x 10(3)C (A = absorbance; C - concentration in M) with a regression coefficient of 0.9998 and a limit of detection, for a probability level of 95% (for K = 3) of 0.1-mu-g ml-1. In the analysis of synthetic samples containing propoxur and 2-isopropoxyphenol, the total concentration of propoxur was determined with a recovery from 94% to 98.3%. The method provides results comparable to those obtained by the batch analysis of natural water samples spiked with propoxur.