INTERFERENCE OF OXIDANTS IN THE DETERMINATION OF PHENOL BY THE 4-AMINOANTIPYRINE AND ULTRAVIOLET RATIO SPECTROPHOTOMETRIC METHODS

A study is made of the interference of the oxidants CIO-, CIO2-, CIO3-, MnO4-, H2O2, Cr2O72-, S2O82-, and NO3- with the 4-aminoantipyrlne (4-AAP) and ultraviolet (UV) ratio methods for the determination of phenol, and a method is described for minimizing this interference by the addition of sodium arsenite, followed by distillation. The nature of the interference essentially Involves oxidation of the phenol, causing low results. The application of the UV ratio method without distillation is limited because of the absorbance of oxidants in the UV region. The results by the 4-AAP method without distillation show that CIO- and MnO4- interfere markedly, H2O2 interferes less strongly, CIO2 and S2O82- do not interfere unless present in fairly large amounts, while CIO3-, Cr2O72-, and NO3- hardly interfere at all. When the solutions are distilled (heated), the interference of CIO2~, H2O2, and S2O82- increases markedly. © 1979, American Chemical Society. All rights reserved.