A validated workflow for drug detection in oral fluid by non-targeted liquid chromatography-tandem mass spectrometry

Abstract

Oral fluid is recognized as an important specimen for drug testing. Common applications are monitoring in substance abuse treatment programs, therapeutic drug monitoring, pain management, workplace drug testing, clinical toxicology, and driving under the influence of drugs (DRUID). In this study, we demonstrate that non-targeted LC-MS/MS with subsequent compound identification by tandem mass spectral library search is a valuable tool for comprehensive detection and confirmation of drugs in oral fluid samples. The workflow developed involves solid-phase extraction and chromatographic separation on reversed phase materials. Mass spectrometric detection is accomplished on a quadrupole–quadrupole-time-of-flight instrument operated with data-dependent acquisition control. The workflow was optimized for 500 μl of neat oral fluid collected with the Greiner Bio-One saliva collection system. The fitness of the developed method was tested and proven by analyzing blank and spiked samples as well as 59 authentic patient samples. We could demonstrate that compounds with logP values in the range 0.5–5.5 are efficiently detected at low nanograms per milliliter concentrations. The true positive and true negative rates of automated library search were equal or close to 100%. The beauty of the non-targeted LC-MS/MS approach is the ability to detect compounds hardly included in routinely applied targeted assays, and this was demonstrated by detecting the synthetic opioid U-47700 in two patient samples. Graphical abstractᅟ Electronic supplementary materialThe online version of this article (10.1007/s00216-018-1504-x) contains supplementary material, which is available to authorized users.

U-47700 and Its Analogs: Non-Fentanyl Synthetic Opioids Impacting the Recreational Drug Market

“…Isomeric pairs exist for both parent drugs and metabolites (e.g., U-48800 vs. U-51754, U-49900 vs. isopropyl-U-47700 vs. propyl-U-47700, and U-47700 vs. N -desethyl-U-49900), and these pairs require special attention and chromatographic separation since their mass data are similar or identical. Methods have also been developed for the detection of U-compounds in alternative matrices, such as oral fluid and hair [ 74 , 75 , 76 ]. U-47700 was identified in oral fluid samples after suspected heroin use [ 77 ], as well as hair in both an intoxication event and a fatality [ 51 , 78 ].…”

Evaluation of swabs from 15 commercially available oral fluid sample collection devices for the analysis of commonly abused substances: doping agents and drugs of abuse

“…Small (<500 Da), basic, lipophilic, neutral, unbound, and unmetabolized drugs are generally expected to be present in oral fluid. [1][2][3][4] Basic substances are especially biased towards higher oral fluid concentrations due to the so-called ion-trapping phenomenon. Such basic drugs are present in plasma ( pH = 7.35-7.45) as neutral molecules, but ionize after diffusion to more acidic oral fluid ( pH = 6.2-7.4), subsequently becoming no longer involved in the equilibrium-driven process of passive diffusion, and thus remaining trapped in oral fluid at increasing total concentrations.…”

Salivary Analysis for Medico-Legal and Forensic Toxicological Purposes

“…In fact police officers, without medical supervision, are not authorised to employ invasive methods but they can collect OF samples. A very comprehensive review of the analysis of drugs of abuse in OF was conducted by Reinstadler et al [22]. Other studies [23] have highlighted the importance of both the sample treatment process and the use of hyphenated instruments in obtaining analytical performances that satisfy current regulations in terms of sensitivity, selectivity and fast confirmatory analysis.…”