Site-specific peak intensity ratio (SPIR) from 1D 2H/1H NMR spectra for rapid distinction between natural and synthetic nicotine and detection of possible adulteration.

1H and 2H NMR spectra of 4 natural and synthetic nicotine samples were collected in a non-quantitative way and site-specific 2H/1H peak intensity ratio (SPIR) was calculated for 12 distinct sites of nicotine. Experimental results illustrated that the SPIRs at sites of 6, 2', and 5'β of natural nicotine were significantly different from those of the synthetic nicotine, and could be used for nicotine authentication as the measured SPIRs were indicative of the site-specific natural isotope fractionation. We demonstrated that this method could be applied to detect adulteration of natural nicotine with as low as 20% synthetic nicotine, without the need to measure the site-specific δD values, which usually required time-consuming quantitative 2H NMR and additional IRMS for the overall 2H/1H isotopic ratio determination. The distinguishable 2H/1H SPIRs of nicotine, which can be quickly measured by NMR in non-quantitative way, can serve as an attractive alternative tool for tobacco authentication. Graphical abstract.