Flow-injection spectrophotometric determination of carbimazole and methimazole

A flow-injection method using spectrophotometric detection at 325 nm, is proposed for the determination of carbimazole or methimazole. The procedures are based on the formation of yellow complexes between these antithyroid drugs and Pd(II) in 0.5 M HC1. Methimazole or carbimazole are determined over the range 1 × 10−5 −5 × 10−4 M. The sampling frequency is 90 h−1. The proposed methods are applied to the determination of methimazole or carbimazole in pharmaceuticals and methimazole added to human urine.