Validation of an analytical method for the detection of ephedrine and its analogues in forensic samples using HPTLC–MS

Abstract

Drug abuse is a global menace in the society. Strict measures are planned and effectuated to dismantle this crime yet a large number of cases of narcotics drugs are seized and referred to forensic science laboratories for analysis. Over the past few years, the misuse of precursor chemicals has increased substantially. Examination of these precursor chemicals, especially ephedrine and its analogues, is a major task for forensic analysts. Though gas chromatography–mass spectrometry (GC–MS) is a well-established technique, it dwindles in the identification of the analogues of ephedrine as they have similarity in molecular weight and structure. The analysis involves time-consuming extraction and derivatization process in sample preparation when used for the identification of isomers. The present paper describes a use of high-performance thin-layer chromatography coupled with mass spectrometry (HPTLC–MS) for the purpose. This technique requires minimum sample preparation; it is a quick and easy methodology with no derivatization and gives a conclusive result for the separation and identification of ephedrine analogues. The drug samples were dissolved in methanol and spotted on Si₆₀ F₂₅₄ thin-layer chromatography (TLC) plate. Good separation of ephedrine from a mixture of ephedrine, pseudoephedrine, and phenylpropanolamine was achieved using the solvent system n-butyl acetate–acetone–n-butanol–5 M ammonia–methanol (4:2:2:1:1, v/v). The separated spot on the TLC was subjected to MS, which identified ephedrine with confirmation.