Separation and determination of chlorophenylpiperazine isomers in confiscated pills by capillary electrophoresis.

A simple capillary electrophoretic method with spectrophotometric UV detection at 236 nm has been developed for the selective separation and determination of 1-(2-chlorophenyl)piperazine (oCPP), 1-(3-chlorophenyl)piperazine (mCPP) and 1-(4-chlorophenyl)piperazine (pCPP) in confiscated pills. Several cyclodextrin derivatives were tested to compose the background electrolyte (BGE). The optimized BGE contained 20 mmol/L phosphoric acid adjusted to pH 2.5 with triethylamine and 10 mmol/L α-cyclodextrin, which provided acceptable resolution of analytes and candidate interferents in less than 15 min. The analyses were performed at constant voltage of 25 kV in 60 cm (effective length 50 cm; 50 μm i.d.) uncoated fused-silica capillary maintained at 25°C with sample injection at 4,826 Pa for 8s. Procaine at a concentration of 0.1mg/mL was used as internal standard (IS). Possible interference from other drugs such as amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxy-N-ethylamphetamine, 1-(3-trifluoromethylphenyl)piperazine and cocaine was also examined. The analytical curves were linear (R(2)=0.9994-0.9995) in the range of 10-200 μg/mL (for oCPP and mCPP) and 20-200 μg/mL for pCPP. Limits of detection (LODs) were 2.0 μg/mL (oCPP), 2.5μg/mL (mCPP) and 3.5 μg/mL (pCPP). Intraday precision at three concentration levels and six replicates of each level (10, 100, 200 μg/mL of each analyte; n=18) was evaluated for the corrected peak area ratio of analyte to IS and the migration times giving RSDs ≤ 4.9%. The accuracy was estimated for mCPP by a recovery test at the same three concentration levels and recoveries varied from 101.0 to 101.6%. The method has been successively applied to the analysis of 17 confiscated pills based mostly on mCPP.