Indirect flame atomic absorption spectrometric determination of papaverine, strychnine and cocaine by continuous precipitation with Dragendorff's reagent

Abstract

A flow injection method for the determination of papaverine, strychnine and cocaine based on the precipitation of ion pairs formed between the alkaloid and Dragendorff's reagent, Bil₄^–, is proposed. The precipitate is obtained by injecting the Bil₄^– complex (precipitating reagent) into a carrier stream containing the alkaloid and is subsequently retained on a filter. In this way, the drugs can be determined over the ranges 1.5–18, 4–60 and 6–100 µg ml^–1 for papaverine, strychnine and cocaine, respectively, with a relative standard deviation of between 1.1 and 2.1% and a sampling frequency of 100 h^–1. The proposed method was applied to the determination of papaverine in pharmaceutical preparations using flame atomic absorption spectrometry.