The New Scanning Mode in Digital Linear Ion Trap Mass Spectrometry for the Detection of New Psychoactive Substances in E-Cigarette Oils

The abuse of new psychoactive substances (NPS) has become a growing global concern, and their illegal addition to commercial e-cigarette oils poses severe threats to human health and potentially results in fatalities. Regulatory control of NPS remains challenging owing to their rapid structural evolution. Meanwhile, laboratory-based detection methods are constrained by long turnaround times, highlighting the necessity of on-site rapid detection for timely interception and response. Mass spectrometry offers superior sensitivity and specificity for trace NPS detection, and a portable mass spectrometer has shown potential for on-site applications. Precursor ion and neutral loss scanning, which enable class-selective detection of unknown analogues via specific functional groups, have not yet been applied to the on-site rapid screening of NPS in e-cigarette oils. In this study, we implemented these two scanning modes in a portable digital linear ion trap mass spectrometer (DLIT-MS) for the first time. Compared with the analogue radio frequency (RF)-driven ion trap mass spectrometer, at the same RF amplitude and ion q-value, DLIT-MS has a deeper pseudopotential well, enabling lower q-values for precursor ions. Additionally, it uses low-voltage rectangular waveforms synthesized by digital circuits, enabling precise frequency control and exceptional flexibility for multimode analysis, and thus is suitable for on-site rapid detection of NPS. Here, four sets of drug standard samples were analyzed using the portable DLIT-MS to characterize the performance of the proposed method. Subsequently, further experiments were conducted with standard solutions of two major classes of NPS: synthetic cannabinoids and fentanyl, along with their analogues. Finally, the method was applied to the detection of illegally adulterated NPS, including etomidate and its analogues, as well as synthetic cannabinoids, in commercially available e-cigarette oil samples. Experimental results demonstrated that precursor ion and neutral loss scanning, when performed on portable DLIT-MS, can effectively identify target compounds and their structurally related derivatives. This finding confirms the application potential of these two scanning modes in portable DLIT-MS for the on-site rapid detection of illegally added NPS in e-cigarette oils.