Rapid confirmation and quantitation of drugs-of-abuse in oral fluid using a low cost, small footprint mass spectrometer

- Quantitation of a range of DoA using a small, low-cost MS is demonstrated.
- In-source fragmentation with variable cone voltage increases specificity.
- Required detection limits for DRUID testing were met for all drugs except THC.

Recent developments in the miniaturisation of mass spectrometry have led to a new generation of low-cost instruments which are making MS a more accessible technology in all areas of analytical science. While the utility of these instruments for qualitative analysis has been demonstrated, their usefulness for quantitative analysis - particularly in complex matrices - has not been proven. Here we describe the development of a rapid LC-MS method for the analysis of drugs-of-abuse in oral fluid using the Waters QDa, a small, low-cost, single quadrupole MS. The method involves direct injection of oral fluid samples followed by a five minute chromatographic run with MS detection. In order to improve the specificity of the method the instrument cone voltage was used to generate in-source fragments of the analytes, these were combined with retention time to confirm the presence of each compound. The final method was tested using synthetic saliva spiked with a mix of twelve drugs-of-abuse at 5-250 ng/mL; LODs were ≤5 ng/mL for all analytes studied except THC and MDA which had LODs of 10 and 25 ng/mL respectively. LOQs for the method were at or below the required cut-off limits for the analysis of oral fluid for drug driving with the exception of THC. The accuracy and repeatability of the method were demonstrated using repeat injections of spiked saliva at 10, 25 and 50 ng/mL; in all cases the repeat injections showed excellent repeatability (typically within 5% RSD) and excellent accuracy (bias typically within ±10%).

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