Study of the behaviour of various phenolic compounds in the 4-aminoantipyrine and ultraviolet-ratio spectrophotometric methods without and with distillation

It is customary in industrial analysis in the determination of phenols by the 4-aminoantipyrine (4-AAP) and ultraviolet-ratio spectrophotometric methods to report the total of phenolic compounds as phenol. A study was therefore made of the behaviour of 36 representative phenolic compounds in the 4-AAP and UV-ratio methods, with and without distillation, to ascertain the apparent recoveries relative to that for phenol. The Fisher phenol analyser was used for the UV-ratio method, which depends upon the bathochromic shift (from about 270 to about 290 nm) usually obtained when the solution of the phenol is made alkaline. The apparent recoveries by the 4-AAP method both with and without distillation varied from 0 to 100%. The apparent recoveries by the UV-ratio method without distillation varied from 0 to 148%, and those with distillation varied from 0 to 110%. Sixteen of the compounds tested without distillation gave less than 10% recovery by the 4-AAP method and eleven gave less than 10% recovery by the UV-ratio method. The results after distillation indicated that several of the compounds did not distil completely.