Developing a qNMR method for purity profiling of crack-cocaine samples seized by police forces in northeastern Brazil
Eduardo de Jesus Oliveira 1 and Rony Anderson Rezende Costa 2
1 Universidade Federal dos Vales do Jequitinhonha e MucurÃÂÂ, Brazil 2 Instituto de PolÃÂÂcia CientÃÂÂfica, Brazil
: Forensic Toxicol Pharmacol 2015, 4:3
Abstract
Illicit use of Crack-cocaine has become a major health issue in Brazil which is currently a large consumer of world's cocaine according to UN statistics. The present work describes the development of a 1H-qNMR method to assay crack cocaine samples seized by police forces in northeastern Brazil. Samples were weighted and dissolved in D2O acidified with DCl. The internal standard used was the sodium salt of 3-(trimethylsilyl)-2, 2, 3, 3,-D-4 propionic acid (TSP-D4). The same samples assayed with the 1H-qNMR method were submitted to analysis by a validated quantification method based on reversed-phase high performance liquid chromatography with diode array detection for comparison of the cocaine content. Also, a GC/MS method was used for confirmation of the impurities detected with the NMR method. The results revealed that the average content of cocaine in the samples was above 70% (w/w). There was a large variability in the purity of samples as determined by both methods (5.2-89.1%, w/w for 1H-qNMR and from 4.9 to 93.8% w/w for the HPLC method). The best correlation between the HPLC and the 1H-qNMR values was obtained when using the integration values of the 3.6 ppm singlet signal corresponding to methyl ester protons (r 2 =0.83). The main impurity detected in the 1H-NMR spectra of the samples was phenacetin, which was found in 84% of the samples. This adulterant was confirmed by GC/MS analysis. The developed 1H-qNMR can be regarded as a simple, convenient and fast screening method to assist in the purity profiling of crack cocaine samples.
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