Oral fluid (OF) is increasingly used as an alternative sample matrix in drug of abuse screening. Screening is commonly performed by immunoassays and results confirmed using laborious gas chromatography–mass spectrometry (GC-MS)–based methods. Therefore, an easy to operate ion trap mass spectrometric (IT-MS) commercial screening method (Toxtyper; Bruker Daltronik, Bremen, Germany) combined with a laboratory-developed sample preparation procedure has been evaluated for their application to OF.Methods:
OF samples were subjected to protein precipitation followed by HybridSPE-Phospholipid extraction. Chromatographic separation was achieved by ultra–high-performance liquid chromatography; MS2/MS3 spectra were recorded by IT-MS and analyzed using a library provided by the manufacturer (Bruker Daltronik). The lower limit of detection, linearity, imprecision, inaccuracy, and specificity (interferences and matrix effects) were investigated for methadone, buprenorphine, pregabalin, fentanyl, amphetamine, 3,4-methylendioxy-N-methylamphetamine, cocaine, acetylcodeine, and nordiazepam, after spiking drug-free OF with these test substances. In addition, concordance between IT-MS results and gas chromatography–tandem mass spectrometry, liquid chromatography–tandem mass spectrometry, or immunoassay (buprenorphine) results was investigated.Results:
No interferences or matrix effects were observed. The lower limit of detection for acetylcodeine, amphetamine, benzoylecgonine, methadone, and nordiazepam was below the common cutoffs for immunological screening assays and comparable to that of GC-MS. Imprecision and inaccuracy, both in- and between-series, were consistently <25%, except for buprenorphine. Toxtyper screening for pregabalin and fentanyl was less sensitive than a targeted liquid chromatography–tandem mass spectrometry assay. A very good concordance was found between the previous analytical approach and the new IT-MS method.Conclusions:
The Toxtyper IT-MS is easy to use and can be applied for the screening of drug of abuse and the qualitative confirmation analysis in OF in a clinical toxicology service. Although intended for qualitative analysis, performance data suggest that the methods investigated may also be applicable for semiquantitative longitudinal follow-up.