Capillary electrochromatographic separation of illicit drugs employing a cyano stationary phase

In this study, we present a capillary electrochromatographic method for separation of basic compounds of interest in forensic science (amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyethylamphetamine, cocaine, codeine, heroin, morphine, and 6-monoacethylmorphine). Several analytical conditions were taken into account to completely separate in the same run the 10 drugs of abuse analyzed. Chromatographic retention, selectivity and efficiency were evaluated in dependence of the type of stationary phase (CN and RP-C₁₈ derivatized silica particles), mobile phase composition, buffer type and pH, sample injection. The optimum separation parameters were set up using a mixture of aqueous sodium phosphate buffer (pH 2.5)/acetonitrile (80/20, v/v) as the mobile phase, 10 kV and 20 °C as applied voltage and capillary temperature, respectively. Under these conditions all the studied analytes were baseline resolved within 20 min. The method performance was investigated in terms of precision, linearity, sensitivity and accuracy to demonstrate the applicability of the developed capillary electrochromatographic system to forensic analysis. Calibration curves provided a good linearity over a working range of 100-1200 ng/mL for all analytes. Limits of detection and quantification were in the range 5-12 ng/mL and 10-30 ng/mL, respectively. Then the method was applied to the analysis of a human urine sample spiked with a basic compounds' mixture. Urine samples' pre-treatment was carried out through a solid phase extraction (SPE) procedure on strong cation exchange (SCX) cartridges.