Assessment of the similarity between in-source collision-induced dissociation (IS-CID) fragment ion spectra and tandem mass spectrometry (MS/MS) product ion spectra for seized drug identifications

Abstract

The use of in-source collision-induced dissociation (IS-CID) with single-stage mass spectrometers has grown in popularity within the field of seized drug analysis as a pseudo-tandem mass spectrometry (MS/MS) analysis to gain structural information about unknown compounds. However, there is currently no statistical assessment of the similarity and thus, the comparability, of IS-CID fragment ion spectra and MS/MS product ions spectra for representative novel psychoactive substances (NPS), such as synthetic cannabinoids, synthetic cathinones, and fentanyl analogs. This study investigates the use of spectral comparisons, breakdown curves, and Pearson product-moment correlations (PPMCs) to assess the similarity between IS-CID fragment ion spectra and MS/MS product ion spectra both visually and statistically. In addition, this study also examines the repeatability of IS-CID fragment ion spectra relative to MS/MS product ion spectra to assess the short-term repeatability of IS-CID fragment ion spectra. The 95% confidence interval average PPMC for the highest pairwise comparison across this study was 0.9294 +/- 0.0106. The optimum comparison range between IS-CID fragment ion spectra and MS/MS product ion spectra was identified between a fragmentor voltage of 150–280 V and a collision energy of 0–22 eV. Similar repeatability of IS-CID fragment ion spectra (15.21%) and MS/MS product ion spectra (14.72%) was also observed. Demonstrating the achievable spectral similarity between IS-CID fragment ion spectra and MS/MS product ion spectra for representative NPS, as well as highlighting the potential deleterious effects of high activation conditions on spectral comparisons, will help inform analysts’ decisions regarding seized drug identifications based on IS-CID fragment ion spectra.