Since two-tiered identification strategy for controlled substance testing that relies on two independent, discerning methods could entirely circumvent the need for forensic laboratory testing and shift testing to the point of seizure, the current project coupled Raman spectroscopy and paper spray ionization mass spectrometry (PSI-MS) on a single instrumental platform.
Both methods are capable of ambient analysis with fieldable instruments, yet Raman is often limited to bulk analysis. Critical to this work is the development of a gold nanoparticle (AuNP)-embedded paper swab to extend the capability of Raman spectroscopy to trace evidence via surface-enhanced Raman scattering (SERS). Plasmonic papers were characterized with respect to SERS signals and compatibility with PSI-MS analysis. Proof-of-principle was established with the identification of five representative drugs, and detection limits on the scale of 1–100 ng were achieved for both PSI-MS and SERS. The integrated SERS-PSI-MS system achieved 99.8 percent accurate chemical identification in a blind study consisting of 500 samples. Additionally, the project demonstrated facile discrimination of several JWH-018 isomers via SERS, even when MS and MS2 spectra were indistinguishable. Successful coupling of SERS and PSI-MS to enable on-site chemical analysis by two independent methods can potentially lead to a desirable paradigm shift in the handling of drug evidence. (publisher abstract modified)