Method for determination of phenylbutazone and oxyphenylbutazone by bromocoulometric titration

A method for the quantitative determination of phenylbutazone and oxyphenylbutazone by bromocoulometric titration is presented. Bromine is generated at the anode and, under the titration conditions applied, it is added quantitatively to the double bond of the enol form of dioxophenyl-pyrazolidine. The titration end-point is detected by the decolorization of methyl orange solution used as the indicator. The results obtained show that the method is reproducible and accurate for the determination of small quantities of these analgesics