3. Results and discussion
3.1. Simon test for methamphetamine
Methamphetamine reacts with acetaldehyde to produce an
enamine intermediate which then reacts with sodium nitroprusside
to produce an immonium salt. This salt can then be hydrolyzed
to a Simon-Awe complex to give a blue colored product [10,23]. At
high concentrations (>1 mg mL1) the blue product remains for 3–
4 min before gradually changing to purple which becomes deeper over time. In this study, the molecular absorption (580 nm [24]) of
these blue products was found to decrease within 3–4 min before
increasing (Fig. 2a). The decrease in absorption seems to relate to the
color change indicating the decomposition of the Simon-Awe
product. At low concentrations of methamphetamine (