Stacking and low-temperature technique in nonaqueous capillary electrophoresis for the analysis of 3,4-methylenedioxymethamphetamine

Low-temperature and ambient-temperature nonaqueous stacking techniques in capillary electrophoresis (CE) are described for the first time. A low-temperature bath was used to control the temperature from ambient to subzero degrees, by which a novel hyphenated method, low-temperature bath-nonaqueous capillary electrophoresis stacking (LTB-NACE stacking) is demonstrated. 3,4-Methylenedioxymethamphetamine (3,4-MDMA) was determined at a concentration of 4.7 × 10^-6 M (at a 92.1% confidence level) by normal nonaqueous capillary zone electrophoresis (NACZE) and this was improved to 2.6 × 10^-8 M and 5.0 × 10^-9 M, respectively, when the NACZE stacking and LTB-NACZE stacking techniques were applied. The content of 3,4-MDMA in an illicit drug and a suspect urine sample was readily detected. Upon application of the LTB to the separation of isomers the resolution (R) for the separation of 2,3-/3,4-MDMA was improved from 0.6 (LTB, 22°C) to 1.6 (LTB, -55° C) and for (+)3,4-MDMA/(-)3,4-MDMA, from 0.4 (LTB, 25°C) to 1.0 (LTB, -10°C).