Potentiometric determination of acid-base contaminations in drugs.

: A potentiometric method for the determination of impurities in pharmaceuticals with acid-base behaviour is proposed. Based on proton balance condition, appropriate equations for the treatment of the data are derived. The latter in combination with Gran's equations allow the determination of acid-base impurities in pharmaceuticals--weak protolytes. The proposed method is quick, accurate and precise. It is suitable both for technical control and for analyses according to the pharmacopoeias.