Rapid assessment of the Illegal-presence of 1,3-dimethylamylamlne (DMAA) In sports nutrition and dietary supplements using ~1H NMR spectroscopy

摘要

1,3-DimethylamyIamine (DMAA) is a stimulant that can be found in pre-workout sports nutrition and dietary supplements. This practice is illegal because DMAA is not a safe food ingredient but rather an unapproved medicinal compound due to its pharmacological action. In order to determine the DMAA content in such products, a nuclear magnetic resonance (NMR) spectroscopic method was developed and validated (DMAA was quantified as DMAA-HCI). For quantification, the collective integral from two of the methyl groups of the molecule in the range § 0.92-0.84 ppm was used. The method was linear over the examined range of 1-21 g/kg (R2 = 0.9937). The recoveries from spiked concentrations (0.1-6 g/kg) ranged between 85% and 105% (96% on average), with a relative standard deviation (RSD) of 1% for an authentic sample. The detection limit was 0.03 g/kg and the quantification limit was 0.08 g/kg (calculated for 75 rrig sample weight). The actual DMAA-HCI content in the sample was quantified using calibration curves (external standardization) or 3,5-dinitrobenzoic acid as single-point internal standard. The developed NMR methodology was applied for the analysis of 16 products, from which 9 samples were found positive (the DMAA-HCi concentration varied between 3.1 g/kg and 415 g/kg). The method can be recommended for routine use in food testing, customs or doping control laboratories.