Abstract: Objective To establish a method that combines a series of techniques including Fourier transform infrared spectrum （FTIR）, gas chromatography-mass spectrometry （GC-MS）, high resolution mass spectrometry and nuclear magnetic resonance spectroscopy （NMR） for identification of unknown substances. Methods The unknown samples （off-white powder and yellow crystal） seized in the actual cases were detected by FTIR, GC-MS （methanol as solvent）, high resolution mass spectrometry （methanol as solvent） and NMR （deuterated methanol as solvent）. Results The mass spectrum characteristic ions m/z of the main components in the samples measured by GC-MS were 219 （base peak）, 363, 307, 304, 275, 145, 131 and 213 （base peak）, 357, 301, 298, 269, 185, 171, 145 and 131, respectively. The accurate mass numbers [M+H]+ measured by high resolution mass spectrometry were 364.203 61 and 358.212 34, respectively. The unknown samples were identified as synthetic cannabinoid new psychoactive substances 4F-MDMB-BUTINACA and MDMB-4en-PINACA after data consultation and database retrieval and comparison, combined with infrared analysis and mass spectrometry data analysis, and their structures were confirmed by 1H-NMR. Conclusion The established multi-technology joint identification method can be used to identify 4F-MDMB-BUTINACA and MDMB-4en-PINACA in unknown samples. This method is fast, convenient, accurate, reliable and practical, and can provide reference for the identification of cases involving such substances in the future.

Key words: forensic medicine, toxicological analysis, new psychoactive substance, Fourier transform infrared spectrum （FTIR）, gas chromatography-mass spectrometry （GC-MS）, high resolution mass spectrometry, nuclear magnetic resonance spectroscopy （NMR）, synthetic cannabinoid