Simultaneous chiral separation of 3,4‐methylenedioxymethamphetamine (MDMA), 3‐4‐methylenedioxyamphetamine (MDA), 3,4‐methylenedioxyethylamphetamine (MDE), ephedrine, amphetamine and methamphetamine by capillary electrophoresis in uncoated and coated capillaries with native β‐cyclodextrin as the chiral selector: Preliminary application to the analysis of urine and hair

A capillary electrophoresis method using native β-cyclodextrin as a chiral selector simultaneously separates and detects the enantiomers of six amphetamine-related substances: ephedrine, amphetamine, methamphetamine, MDMA, MDA, and MDE. Optimized conditions (pH 2.5 phosphate buffer, uncoated capillary, 10 kV) achieve good resolution and chiral selectivity for all analytes. Detection limits are better than 0.2 μg/mL, with high precision (intra-day migration time relative standard deviation < 0.8%) and linearity from 0.156 to 40 μg/mL. After liquid-liquid extraction, urine samples can be analyzed below the 500 ng/mL NIDA cut-off. For hair samples, field-amplified sample stacking enables chiral determination of MDMA, MDA, and MDE at concentrations found in real ecstasy users.

Study at a glance

Abstract

Abstract The importance of the chiral analysis of amphetamine‐related substances in both clandestine preparations and biological samples is widely recognized. For this purpose, capillary electrophoresis was successfully applied by several authors, but only few reports concerned ring‐substituted amphetamines, which represent the main components of “ecstasy”, a widely abused “recreational” substance. In the present work, the simultaneous chiral analysis of ephedrine, amphetamine, methamphetamine, 3,4‐methylenedioxymethamphetamine (MDMA), 3‐4‐methylenedioxyamphetamine (MDA) and 3,4‐methalenedioxyethylamphetamine (MDE) is reported, by using capillary electrophoresis with native β‐cyclodextrin (15 m M ) as the chiral selector. After preliminary tests at different pH values (phosphate buffer 100 m M , pH 2.5–9.0) and with bare or coated fused‐silica capillaries, the optimized conditions were: pH 2.5 phosphate, uncoated capillary (45 cm × 50 μm inner diameter), potential 10 kV. Detection was either by fixed wavelength (200 nm) or multiwavelength (190–400 nm) UV absorbance. Under these conditions, good resolution was obtained for all the analytes, with excellent chiral selectivity and efficiency. The sensitivity for the individual enantiomers was better than 0.2 μg/mL, analytical precision was characterized by relative standard deviation values < 0.8% (⩽ 0.15% with internal standardization) for migration times intra‐day and < 2.0% (⩽ 0.54% with internal standardization) day‐to‐day; linearity, in the range 0.156–40 μg/mL, and accuracy were also satisfactory. After a simple liquid‐liquid extraction, urine samples could be analyzed with a sensitivity well below the recommended NIDA cut‐off of 500 ng/mL. For hair samples, it was necessary to increase the sensitivity by applying a field‐amplified sample stacking procedure, which allowed the chiral determination of MDA, MDMA and MDE at concentrations occurring in real samples from ecstasy users, with the possibility of recording UV spectra of the peaks.