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).