Determination of cocaine and its main adulterants in seized drugs from Rio Grande do Sul, Brazil, by a Doehlert optimized LC-DAD method

Abstract

The main reason for the increasing cocaine consumption in South America is the high consumption of drugs in Brazil, which is the largest market on the continent. In light of this, the Brazilian Federal Police (BFP) started implementing its own drug chemical profiling program, the PeQui project, aiming to provide useful technical-scientific information about the drug scenario in the country. In this article, a liquid chromatography with a diode array detector (LC-DAD) method was developed through Doehlert optimization for the analysis of cocaine seized in the state of Rio Grande do Sul, Brazil, by the Brazilian Federal Police. In addition to cocaine, the main cocaine adulterants (diltiazem, benzocaine, levamisole, caffeine, phenacetin, lidocaine and dipyrone) were also evaluated. Through Doehlert optimization relating to the resolution and total area, a mobile phase consisting of acetonitrile : water (isocratic mode) with phosphate buffer (pH 8.3) was chosen. Fifty eight cocaine samples seized in 2013–2015 were analyzed. The average cocaine content was 45% of the drug weight and the only adulterants detected were levamisole, phenacetin and caffeine. Levamisole was detected only in salt cocaine samples and low concentrations (below 0.1 mg g⁻¹), whereas phenacetin was detected in base form cocaine in higher concentrations. Caffeine was the only adulterant detected in both the salt and base forms, and was also at low concentrations. These results showed that the drugs seized in this Brazilian state had, on average, a lower cocaine content in relation to the rest of the country.