Since 2006, the South Australian Government has been conducting roadside oral fluid testing of drivers for the illicit drugs methylamphetamine (MA), methylenedioxymethylamphetamine (MDMA) and δ9-tetrahydrocannabinol (THC) using the Securetec Drugwipe II Twin and Alere DDS 805 AP saliva collection kit. Forensic Science South Australia carries out the confirmatory analysis by LC/MS for the positive test results of oral fluid roadside testing along with the pre-screened ELISA positive road traffic accident blood samples. The number of blood and oral fluid samples received in the laboratory has been steadily increasing during this time, and over 10,000 samples were received in 2014. The proportion of positive results from these samples has also been increasing over the decade of driver drug testing, and this data is presented.A simple and efficient method has been developed for the analysis of the three drugs using Biotage Isolute® SLE+ 96-well plates. Sample preparation included 1:1 dilution with a dilute ammonia solution for buffered oral fluids (1:3 dilution for blood samples), and addition of deuterated internal standards. Samples were loaded onto the phase, left to absorb for 5 min then eluted with methyl t-butyl ether (MTBE). The samples were evaporated and reconstituted in methanol. LC/MS analysis was performed on an AB Sciex 5500 Q-Trap in positive ion mode, monitoring 3 transitions for each analyte. Separation was achieved on a Restek Ultrabiphenyl 50 × 2.1 mm column with a gradient system of acetonitrile/0.1% formic acid over 5 min.Method validation and recoveries were carried out on drug free ante mortem blood and DDS buffer solution provided by Alere, Australia. Recoveries above 80% were achieved for MA and MDMA at a concentration of 25 ng/mL, whilst recoveries of greater than 65% were achieved for THC at 4.5 ng/mL. Accuracy and precision were acceptable down to the LLOQ for all three analytes (5, 5 and 1 ng/mL for MA, MDMA and THC, respectively). Mean matrix effects were 1.0, 0.97 and 0.78 in DDS buffer and 0.96, 0.96 and 0.62 in blood for MA, MDMA and THC, respectively. Linearity was achieved up to 1250 ng/mL for MA and MDMA, and 112 ng/mL for THC (r2 > 0.999 for all analytes). The method is designed for easy transfer to an automated liquid handling platform.
- Oral fluid