TY - JOUR
T1 - Determination of cocaine and its metabolites using cation-selective exhaustive injection and sweeping-MEKC
AU - Su, Hsiu L.
AU - Feng, Lan I.
AU - Jen, Hsiu Ping
AU - Hsieh, You-Zung
PY - 2008/12/3
Y1 - 2008/12/3
N2 - We have employed a high-sensitivity on-line preconcentration method, cation-selective exhaustive injection (CSEI) and sweeping MEKC, for the analysis of cocaine, benzoylecgonine, norcocaine, and cocaethylene. We monitored the effects of several of the CSEI-sweeping-MEKC parameters - including the pH, the concentrations of SDS and organic modifier, the injection length of the high-conductivity buffer, and the injection time of the sample - to optimize the separation process. The optimal BGE was 100mM phosphoric acid (pH 1.8) containing 75mM SDS with 10% 2-propanol and 10% tetrahydrofuran as the organic modifier. In addition, electrokinetic injection of the sample at 15 kV for 900 s provided both high separation efficiency and enhanced sweeping sensitivity. The sensitivity enhancements for cocaine, norcocaine, and cocaethylene ranged from 2.06×104 to 3.96×104; for benzoylecgonine it was 1.75×103; the coefficients of determination exceeded 0.9958. The LODs, based on an S/N ratio of 3:1, of sweeping-MEKC ranged from 33.5 to 52.8 ng/mL; in contrast, when using CSEI-sweeping-MEKC the sensitivity increased to range from 29.7 to 236 pg/mL. Under the optimal conditions, we analyzed cocaine in a human urine sample prepared using off-line SPE to minimize the influence of the matrix. The recovery of the SPE efficiency was satisfactory (ca. 74.9-87.6%). Our experimental results suggest that, under the optimal conditions, the CSEI-sweeping-MEKC method can be used to determine cocaine and its metabolites with high sensitivity in human urine.
AB - We have employed a high-sensitivity on-line preconcentration method, cation-selective exhaustive injection (CSEI) and sweeping MEKC, for the analysis of cocaine, benzoylecgonine, norcocaine, and cocaethylene. We monitored the effects of several of the CSEI-sweeping-MEKC parameters - including the pH, the concentrations of SDS and organic modifier, the injection length of the high-conductivity buffer, and the injection time of the sample - to optimize the separation process. The optimal BGE was 100mM phosphoric acid (pH 1.8) containing 75mM SDS with 10% 2-propanol and 10% tetrahydrofuran as the organic modifier. In addition, electrokinetic injection of the sample at 15 kV for 900 s provided both high separation efficiency and enhanced sweeping sensitivity. The sensitivity enhancements for cocaine, norcocaine, and cocaethylene ranged from 2.06×104 to 3.96×104; for benzoylecgonine it was 1.75×103; the coefficients of determination exceeded 0.9958. The LODs, based on an S/N ratio of 3:1, of sweeping-MEKC ranged from 33.5 to 52.8 ng/mL; in contrast, when using CSEI-sweeping-MEKC the sensitivity increased to range from 29.7 to 236 pg/mL. Under the optimal conditions, we analyzed cocaine in a human urine sample prepared using off-line SPE to minimize the influence of the matrix. The recovery of the SPE efficiency was satisfactory (ca. 74.9-87.6%). Our experimental results suggest that, under the optimal conditions, the CSEI-sweeping-MEKC method can be used to determine cocaine and its metabolites with high sensitivity in human urine.
KW - Cocaine and its metabolites
KW - CSEI-sweeping-MEKC
KW - On-line preconcentration
KW - Sweeping-MEKC
UR - http://www.scopus.com/inward/record.url?scp=56849119815&partnerID=8YFLogxK
U2 - 10.1002/elps.200800167
DO - 10.1002/elps.200800167
M3 - Article
C2 - 18924106
AN - SCOPUS:56849119815
VL - 29
SP - 4270
EP - 4276
JO - Electrophoresis
JF - Electrophoresis
SN - 0173-0835
IS - 20
ER -