Extraction of dried oral fluid spots (dofs) for the identification of drugs of abuse using liquid chromatography tandem mass spectrometry (lc-ms/ms)

Abstract Dried matrix spots (DMS) have been utilized as an alternative sample collection method for drug identification in different biological specimens in clinical and forensic toxicology scenarios. Oral fluid has demonstrated its potential to establish recent drug use in instances such as driving under the influence of drugs or workplace drug monitoring programs. Moreover, this matrix has become an excellent choice over invasive or prone to adulteration approaches, like blood or urine collection. The possibility of drying oral fluid on a paper substrate has open newer opportunities to facilitate sample distribution and analysis. In this study, a dried oral fluid spots (DOFS) method was used to investigate its performance for the analysis of a suite of drugs of toxicological interest. A direct liquid extraction from the paper substrate was assessed, and the detection and quantification were conducted using liquid chromatography-tandem mass spectrometry instrument. Amphetamine, methamphetamine, ketamine, benzoylecgonine, and mitragynine were selected as target drugs to evaluate the DOFS method. Figures of merit including selectivity, matrix effects, recovery (average of 82%, with the exception of mitragynine – 55%), process efficiency, LOQ (0.2 ng/mL), linearity carry over, intraday (3.2–8.4%) and inter-day precision (7.3–18.8%), accuracy (−1.0 to −12.2), and stability of DOFS samples (35 days) are presented. The DOFS method extraction capability was compared against a commercially available weak anion exchange (WAX-S) tips, and the results are presented herein. The method was also successfully applied to eight blind specimens to demonstrate proof of applicability and fit of purpose.