Determination of chiral amphetamine in seized tablets by indirect enantioseparation using GC–MS

Abstract

The illegal production of amphetamine and its derivatives has rapidly increased in the last years to provide the increasing demand all over the world. Since amphetamine is chiral, its enantiomers have different pharmacological activities. The present work aims to study the enantiomeric profile of amphetamine in several batches of tablets seized from the illegal market. The R and S antipodes were first converted to diastereomers by reaction with trifluoroacetyl-l-prolyl chloride (L-TPC) as chiral reagent. The obtained diastereomers were then full separated by gas chromatography with a resolution factor RS of 1.69, then characterized by mass spectrometry. Both S and R-amphetamine showed similar contents in all investigated samples, with a slight excess of the more active S eutomer. The calculated enantiomeric excess (ee%) values are all positive in the range 0.60–9.72%. The total concentration of amphetamine was from 36.44 to 96.22 mg/g in all tablets. The seized materials showed also the presence of some other ingredients used as additives in manufacturing the tablets such as caffeine, phenazocine, diphenhydramine, dibutyl phthalate and 9-octadecenamide. These findings confirmed that the synthesis of amphetamine used in these tablets was performed using inexpensive and achiral starting substances.

Keywords

• R and S-amphetamine
• Chiral separation
• Derivatization
• GC–MS
• Seized tablets