Simultaneous Spectrophotometric Determination of o-Aminophenol and p-Aminophenol Using H-Point Standard Addition Method -Application to Real Waters

H-point standard addition method (HPSAM) has been applied to the simultaneous determination of o-aminophenol (oA) and p-aminophenol (pA) isomers in binary mixtures. The method is based on the Schiff's base formation of aminophenols with 1,2-naphoquinone sulphonate (NQS) as a chromogenic reagent in the presence of micellar cityltrimethyl ammonium bromide (CTAB) and sodium carbonate. The results showed that simultane ous determinations could be performed with the ratios 0.4 : 2.0 and 4.0 : 2.0 measured at pair of wavelengths (480 and 610) nm with recovery % range 94.75-104.37 % and precision better than 4.0 % when oA considered as analyte and pA as interferent, and a ratio 0.4 : 0.2 and 4.0 : 2.0 measured at 455 and 540 nm with recovery % range 95.37-105.0 % and precision better than 4.0 % when pA considered as analyte and oA as interferent.