Rapid indirect determination of very low levels of cocaine by tandem on-line continuous separation and inductively coupled plasma atomic emission spectrometric detection

Abstract

A very sensitive, precise and automated method is proposed for the indirect determination of cocaine. The method is based on selective extraction into chloroform of the protonated alkaloid as an ion pair with Dragendorff reagent; BiH₃ is generated directly from the organic phase and the volatile species is brought to an ICP-AES system for bismuth detection. Both separation steps, extraction and gas–liquid separation, are accomplished in a continuous manner with on-line final ICP-AES detection. The optimum chemical, continuous flow and instrumental variables were determined. The proposed method allows the determination of cocaine over a wide range of concentration (20 ng ml^–1–100 µg ml^–1) and the precision at a concentration of 0.5 µg ml^–1 was 3%. The method was applied to the determination of cocaine in confiscated samples.