Toxicological Drug Screening using Paper Spray High-Resolution Tandem Mass Spectrometry (HR-MS/MS).

Immunoassays and high-performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) are both widely used methods for drug screening in toxicology. We investigated an alternative approach for rapid drug screening: paper spray MS (PS-MS). In paper spray, the biofluid sample is spotted onto a paper substrate. Upon application of a spray solvent and an electric potential, extraction and ionization occur directly from the paper without any need for additional sample preparation. We developed two paper spray high-resolution MS/MS targeted drug screening assays using a quadrupole-orbitrap mass spectrometer, one the positive ion mode and one in the negative ion mode. In the positive ion mode, over 130 drugs and drug metabolites were semi-quantitatively screened at sub-toxic concentrations in a single 2.5 min analysis. Limits of detection and calibration performances for each target compound are reported. The PS-MS/MS assay was tested on authentic postmortem specimens, and its screening ability and semi-quantitative performance were evaluated against independent LC-MS-MS screening and confirmation assays with good agreement. The paper spray MS/MS showed good qualitative agreement with LC-MS-MS; the true positive rate of paper spray MS/MS was 92%, and the true negative rate was over 98%. The quantitative results between the two methods were also acceptable for a screening application; Passing-Bablok regression yielded a slope of 1.17 and a Pearson's correlation coefficient of 0.996. A separate PS-MS/MS negative ion screening method was also developed for a small panel of barbiturates and structural analogs, demonstrating its potential for acidic drug detection and screening.