Rapid orthogonal screening of forensic drugs using a compact UHPLC-PDA/SQD; a complement to GC-MS

With the recent development of hand-held and miniature mass spectrometers, low cost and compact mass detectors have become more available and accessible for on-site and routine laboratory use. Here we present a rapid ultra-high performance liquid chromatography-photodiode array/mass spectrometry (UHPLC-PDA/MS) method for the routine screening of a wide variety of illicit drugs using a small and cost effective single quadrupole MS (SQD) with electron spray ionization (ESI). Two libraries for common drugs of forensic interest, a PDA library including retention time (RT) and PDA spectra and a MS library including RT and [M+H]⁺/[M-H]^-, were developed. Using a BEH phenyl column and gradient elution of acetonitrile and 0.1% formic acid, drugs of forensic interest were detected within 8.5min and identified based on their RT/RRT to an internal standard (Codeine-d₆), UV spectrum, and/or MS spectrum/(de)protonated molecular mass. The method proved to be efficient, reproducible, and sensitive with a limit of detection (LOD) ≤0.5μg/mL for untargeted screening using PDA and MS in full scan mode and ≤0.1μg/mL for targeted screening by MS in select ion recording (SIR) mode. Improved isomer discrimination was achieved, when a second injection and separation by a charged column (CSH C₁₈) was incorporated into the same acquisition sequence. The method was applied to 20 seized drugs with similar detection limits and identifications by GC-MS. Using an orthogonal separation technique and dual detection systems, the UHPLC-PDA/SQD method serves as an attractive technique for a direct and fast screening of illicit drugs with excellent discrimination power and detection capacity. The developed method can be an alternative screening method to GC-FID and complementary technique to GC-MS for routine forensic drug screening.