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

Abstract

CE methods with capacitively coupled contactless conductivity detection (C(4)D) 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-C(4)D 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 (18C6H(4)), 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 18C6H(4) 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-C(4)D method was successfully applied to urine samples of athletes for the identification of enantiomers of the detected stimulants.

Contactless conductivity detection for analytical techniques: Developments from 2010 to 2012

“…were shown feasible in chiral CE . Various enantioselective agents and their combinations were examined for optimization of baseline separations of the chiral isomers and the analysis of extracts of urine from athletes was demonstrated . Amino acids, which are usually derivatized and subsequently visualized using LIF detection, were detected in their bare cationic form in highly acidic buffer solutions in various body fluid samples .…”

New approaches in sensitive chiral CE

“…When these LODs were compared with those of two previous works by UV detection, this method presented up to 400 times lower LOD in in vitro assays. On the other hand, three EKC‐C 4 D methods have been described recently for the enantiomeric separation of stimulating drugs mixtures, such as (i) amphetamine and methamphetamine, (ii) ephedrine and pseudoephedrine, and (iii) norephedrine and norpseudoephedrine . In this work, various enantioselective agents and their combinations were examined for optimization of baseline separations of the stereoisomers.…”

Enantiomeric separations of illicit drugs and controlled substances using cyclofructan‐based (LARIHC) and cyclobond I 2000 RSP HPLC chiral stationary phases

“…In sports, drugs of abuse can provide unfair advantages, thus they are prohibited by the World Anti‐Doping Agency (WADA) . These performance enhancing drugs can be produced as racemates or enantiomerically enriched compounds depending on the method of synthesis and purification.…”

“…There have been reports on a variety of analytical methodologies for separating enantiomers of illicit drugs and controlled substances, including gas chromatography (GC), high performance liquid chromatography (HPLC), capillary electrophoresis (CE), GC‐MS, LC‐MS, and CE‐ESI‐MS . One approach may be superior to another depending on the goal of the investigator and the nature of the problems to be solved.…”