Identification of methylhexaneamine by GC high-resolution TOFMS and soft ionization.

UNLABELLED: Methylhexaneamine (MHA) is a stimulant that is added to dietary supplements and its safety is an on-going debate, prompting the World Anti-Doping Agency to add it to the 2010 prohibited list. Gas chromatography-low resolution mass spectrometry (GC-MS) with electron ionization (EI) requires derivatization to convert MHA into a less volatile compound, and a 2-3 min solvent delay to prevent filament damage. Without derivatization, the EI mass spectrum of MHA, which exhibits an abundant immonium ion at m/z 44 and no other fragment ions with relative intensity >10%, is very similar to the EI mass spectra of 2-aminoheptane, 1,4-dimethylamylamine, and n-hexylmethylamine. When using derivatization with trifluoroacetic anhydride (TFAA) and GC-high resolution time-of-flight mass spectrometry with soft ionization, the derivatized MHA diastereoisomers can be distinguished from the trifluoroacetyl-derivatives of 1-aminoheptane, 2-aminoheptane, 1,4-dimethylamylamine (1,4-DMAA) and n-hexylmethylamine. Several nutritional supplements were analysed for MHA by this technique and the results of the measurements are presented here.

KEYWORDS: GC high-resolution TOFMS; Soft-ionization; Methylhexaneamine; Nutritional supplements.