Solid-phase extraction of antipyrine dye for spectrophotometric determination of phenolic compounds in water

In order to determine phenolic compounds in water, we propose a method based on the reaction of phenolic compounds with 4-aminoantipyrine in the presence of peroxodisulfate at pH 10 to form antipyrine dye and the solid-phase extraction of dye with a Varian Bond Elut Plexa cartridge. Dye collected on the cartridge is eluted with acetonitrile and the absorbance is measured at 475 nm. In our experiments, recovery ratios of >90% were obtained for phenol, o-aminophenol, m-aminophenol, o-methoxyphenol, m-methoxyphenol, p-methoxyphenol, o-cresol, m-cresol, o-chlorophenol, m-chlorophenol, p-chlorophenol, 2,5-dimethylphenol, and 2,4-dichlorophenol. The calibration curve obeyed Beer's law in the range 0 - 0.30 µg ml(-1) phenol. The precision of repeated tests (n = 4) was 1.7% of the phenol solution (0.10 µg ml(-1)); the detection limit was 0.0011 µg ml(-1). Recovery tests using river water, waste water, and sewage influent gave highly satisfactory results.