1. Introduction
Methamphetamine is a synthetic stimulant which affects the
central nervous system [1]. It is increasingly abused and has caused
serious health and social problems. It is usually called ‘‘crank’’ if in
the form of the powder hydrochloride salt, ‘‘Yaba’’ in Thai when in
the form of tablets, and ‘‘Ice’’ in its clear crystal form. This illegal
drug has been classified as a Category I narcotic under the Narcotic
Act B.E. 2522 of Thailand, while it has been reclassified from a Class
B to a Class A Schedule 2 drug under The Misuse of Drugs Act 1971
(UK) in 2007 [2].
Colourimetric presumptive tests are common methods used for
field test. The Marquis and Simon presumptive chemical tests are
recommended for methamphetamine by the United Nations
International Drug Control Programme [1]. The Marquis test
produces an orange-brown reaction,