UV-Spectrometric Determination of Total Phenols Using Diazotized Sulfanilic Acid

Resumo

Phenolic compounds, including nitro- and chlorophenols, in neutral aqueous solutions react with diazotized sulfanilic acid. The molecular absorption coefficients of azo dyes obtained from various phenols in the range 360‒380 nm are quite close, which ensures the determination of the total concentration of phenols as C₆H₅OH. Under optimized conditions, the systematic errors in the analysis of model mixtures did not exceed 30 rel. %. They may be due to either the difference in molar absorption coefficients, or the delayed formation or instability of some azo dyes, and also due to the influence of reducing agents and arylamines. The procedure may become a good alternative to the determination of the phenolic index of sewage waters by the reaction with 4-aminoantipyrine.