Flow injection spectrophotometric determination of propoxur with diazotized 4-aminobenzoic acid

A flow injection spectrophotometric method for the determination of propoxur with diazotized 4-aminobenzoic acid as the coupling agent was developed. The determination involves on-line hydrolysis at room temperature of the propoxur with sodium hydroxide. The resulting 2-isopropoxyphenol is coupled with diazotized 4-aminobenzoic acid in order to achieve an appropriate selectivity and sensitivity to the spectrophotometric measurements. The calibration curve is linear over the range 1-10 mgL(-1) of propoxur. The proposed method has provided a detection limit of 0.15 mgL(-1) of propoxur and a sample frequency of 120 injections per hour. The relative standard deviation of six independent determinations of a sample containing 5 mgL(-1) propoxur was 0.74%. The suitability of the proposed procedure for the determination of propoxur in commercial pesticide formulations was studied. The procedure provides results comparable to those obtained by the liquid chromatography analysis.