The increase in number, diversity and potential toxicity of drugs is a major concern; it also presents significant challenges for forensic laboratories who are involved in the analysis of seized substances and need to turnaround results quickly. Consequently, analytical methods that can provide fast, reliable results are of interest. Traditional analytical workflows include colorimetric, or TLC screening followed by confirmatory analysis using more selective methods e.g., GC-MS. The aim of this study was to assess the potential of an alternative workflow comprising a rapid screen based on Atmospheric Solids Analysis Probe-Mass Mass Spectrometry (ASAP-MS), followed by confirmation using UPLC-Time of Flight-MS (UPLC-ToF-MS).

Certified reference material (CRM), pharmaceuticals and seized materials were analysed using the RADIAN-ASAP (Waters) – a compact, direct analysis device combining ASAP with MS. Seized samples (tablets, pills, powders) were prepared by dilution with methanol. A glass capillary was dipped into each sample before being inserted into the instrument. The system was operated in full scan MS mode and data collected at four cone voltages (15, 25, 35, 50V). Data were processed in real-time and compared to a spectral library prepared using the same conditions. A match score of 850 (from a maximum 1000) was applied as the threshold for a positive identification. Analysis time was ∼30sec.

The same samples were analysed by UPLC-ToF-MS, following further dilution. The confirmation method comprised a UPLC I-Class coupled with an ACQUITY RDa detector (Waters). Chromatographic separation was achieved in 9.5min and accurate mass data was acquired in full scan (positive ionization with fragmentation). Resultant data were compared with a library comprising>100 drug substances. Identification was based on retention time (±0.35min of reference retention time), detection of a precursor mass, and the presence of at least one diagnostic fragment ion.

The ASAP ionization process was demonstrated to be similar to atmospheric pressure chemical ionization, whereby a heated desolvation gas is used to volatilize the sample and a corona discharge to ionize. This resulted in the protonated species for most of the drugs analysed in this study. Application of increasing cone voltages resulted in a spectral fingerprint for each drug, comprising precursor and fragment ions. In the absence of chromatographic separation, this provided increased specificity.

The performance of the rapid ASAP-MS screen was initially evaluated by analysis of CRM (67 samples). For identified substances, match scores were all>870; sensitivity and specificity of the technique were both>95%.

Pharmaceutical preparations (10) and seized material (80) were analysed by ASAP-MS and UPLC-Tof-MS (blinded analysis, two independent scientists). Overall, there was excellent qualitative agreement with concordance for>90% of the drugs detected. Where discrepancies were observed, this was owing to differences in the content of the respective reference libraries, or a difference in the sensitivity of detection (4 samples gave match scores below the minimum threshold applied for the rapid screen). Two of the pharmaceutical preparations did not yield any match with either analytical technique but gave a visible peak by UPLC-Tof-MS. The data was submitted to the structural elucidation tools of the software which returned a proposal. This was subsequently confirmed following analysis of CRM.

ASAP-MS is a rapid, yet accurate and easy-to-use screen. It can identify single, or multiple components, in seized materials and shows potential for a rapid triage of samples to improve laboratory workflow. The UPLC-ToF-MS method used as the reference technique for these studies has also been demonstrated to be a powerful complementary (or standalone) technique, offering confirmation of identity through accurate mass together with the potential to identify unknown substances through structural elucidation.