Drugs of abuse in oral fluid collected by two different sample kits--stability testing and validation using ultra performance tandem mass spectrometry analysis

Abstract

Oral fluid (OF) is an alternative matrix for monitoring drugs of abuse in workplace, clinical toxicology, criminal justice, and driving under the influence of drugs (DUID). OF is suitable for detection of drugs that have been taken recently. It is unproblematic to observe the collection and hence avoid the possibility of the samples being tampered. OF often contains compounds in low concentrations, and small volumes are often collected. It is therefore necessary to have a sensitive, multi component method for drug detection. In this study an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method has been developed. The samples were prepared by liquid-liquid extraction (LLE) with ethyl acetate/heptane (4:1) and the separation was achieved by an Acquity HSS T3-column (2.1 mm × 100 mm, 1.8 μm particles). Mass detection was performed by positive ion mode electrospray MS-MS. 32 drugs of abuse were determined with a cycle time of 9 min. Stability of drugs in oral fluid before analysis is an important factor that must be evaluated for each sampling device. The collection devices Intercept(®) and StatSure Saliva Sampler™ were tested using pools of real samples containing various drugs. The testing showed that 6-MAM (6-acetylmorphine), cocaine and zopiclone were the least stable compounds. In the testing for short term stability, StatSure Saliva Sampler™ showed better results. The testing of 1 year of storage at -20°C showed that most of the compounds were stable for both sampling devices, except for 6-MAM, cocaine and zopiclone. Samples of OF should be analysed as soon as possible after collection, and they should be kept frozen if immediate analysis is not possible.