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Enantiomeric separation of some common controlled stimulants by capillary electrophoresis with contactless conductivity detection

Authors

  • Thitirat Mantim,

    1. Flow Innovation-Research for Science and Technology Laboratories (First Labs), Mahidol University, Bangkok, Thailand
    2. Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
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  • Duangjai Nacapricha,

    1. Flow Innovation-Research for Science and Technology Laboratories (First Labs), Mahidol University, Bangkok, Thailand
    2. Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
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  • Prapin Wilairat,

    1. Flow Innovation-Research for Science and Technology Laboratories (First Labs), Mahidol University, Bangkok, Thailand
    2. Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand
    3. National Doping Control Centre, Mahidol University, Bangkok, Thailand
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  • Peter C. Hauser

    Corresponding author
    1. Department of Chemistry, University of Basel, Basel, Switzerland
    • Department of Chemistry, University of Basel, Spitalstrasse 51, 4056 Basel, Switzerland Fax: +41-61-267-1013
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Abstract

CE methods with capacitively coupled contactless conductivity detection (C4D) were developed for the enantiomeric separation of the following stimulants: amphetamine (AP), methamphetamine (MA), ephedrine (EP), pseudoephedrine (PE), norephedrine (NE) and norpseudoephedrine (NPE). Acetic acid (pH 2.5 and 2.8) was found to be the optimal background electrolyte for the CE-C4D system. The chiral selectors, carboxymethyl-β-cyclodextrin (CMBCD), heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMBCD) and chiral crown ether (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid (18C6H4), were investigated for their enantioseparation properties in the BGE. The use of either a single or a combination of two chiral selectors was chosen to obtain optimal condition of enantiomeric selectivity. Enantiomeric separation of AP and MA was achieved using the single chiral selector CMBCD and (hydroxypropyl)methyl cellulose (HPMC) as the modifier. A combination of the two chiral selectors, CMBCD and DMBCD and HPMC as the modifier, was required for enantiomeric separation of EP and PE. In addition, a combination of DMBCD and 18C6H4 was successfully applied for the enantiomeric separation of NE and NPE. The detection limits of the enantiomers were found to be in the range of 2.3–5.7 μmol/L. Good precisions of migration time and peak area were obtained. The developed CE-C4D method was successfully applied to urine samples of athletes for the identification of enantiomers of the detected stimulants.

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