Investigation into the applications of the NeoSAL (TM) oral fluid collection device for determination of amphetamine and methamphetamines

Background/Introduction: Oral fluid (OF) is no longer considered an alternative matrix, and is often collected when monitoring compliance with drug treatment programmes, in workplace and roadside drug testing. New guidelines for OF testing are constantly emerging, making it important to critically assess new collection devices. The newest collection device is the Neogen® NeoSAL™ device. It is a pad-based device that contains 2.1 mL of buffer, and is stated to collect 0.7 mL of oral fluid. No data on drug recoveries and applicability of the device exists and this is what this study aimed to change.

Objective: The objective of the study was to evaluate the applicability and advantages of the new Neogen® device for the analysis of amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA), 3,4- methylenedioxyamphetamine (MDA) and 3,4-methylenedioxy-N-ethyl-amphetamine (MDEA) in OF samples. A partial validation was performed according to SWGTOX guidelines, collection volume adequacy and drug recoveries assessed, in accordance with cut-offs recommended by the European Workplace Drug Testing Society (EWDTS).

Method: Analytes were extracted using mixed-mode (UTC CleanScreen®) SPE followed by gas chromatrographymass spectrometry (GCMS) for amphetamines in OF. The analysis used the respective deuterated compounds as internal standard (IS; 35 ng/0.7 mL of OF), over a calibration range of 2–200 ng/0.7 mL of OF. Samples were analysed in quadruplicate. A sample volume of approximately 2.8 mL (assuming 2.1 mL of buffer and 0.7 mL of OF) as per the manufacturer’s specification was used. Validation parameters assessed included: linearity, limits of detection (LOD) and quantitation (LOQ), bias and precision (15, 30, 100 ng/0.7 mL of OF), interference, carryover, and processedsample stability (15 and 100 ng/0.7 mL of OF). The device was assessed gravimetrically to establish collection volume adequacy as this is often overlooked in evaluation of collection devices. The drug recovery was assessed at two concentrations; 30 and 100 ng/0.7 mL of OF. Two methods were followed when assessing drug recoveries from the NeoSAL™ device: the collection pad was dipped into spiked OF and 0.7 mL of spiked OF was pipetted onto the pad.

Result: Calibration graphs were linear, showing r2 values ≥0.999 (n = 10) for all curves. LOD was determined to be 0.71 ng/0.7 mL of OF (where S/N ≥3, n = 5); LOQ was set at 2 ng/0.7 mL of OF. Carryover was not seen for concentrations up to 1500 ng/0.7 mL of OF. None of the 40 drugs investigated showed interferences. Inter-day analytical accuracy (bias) and precision (n = 5) were 81–98%, and ≤3% for all three QC concentrations. The analysis of processed-samples showed analytes were stable for up to 72 hours on the autosampler (19 ±0.5 °C), showing drug concentrations 67–105% and 84–97% of Day 0 concentrations at the two QCs over the testing period. Drug recoveries ranged from 63–81% for 30 ng/0.7 mL (n = 8), and 64–81% for 100 ng/0.7 mL (n = 8), which were higher than Intercept® i2™ recoveries (range 44–80%, n = 8) found in previous work. Gravimetric work (n = 25) carried out shows that the NeoSAL™ device collects an average of 0.84 mL (ranging from 0.61–1.1 mL, median 0.89 mL, %CV ≤15%) of OF compared to the stated 0.7 mL.

Conclusion/Discussion: Novel data was collected on the newest commercially available OF collection device. Although it is stated that the collection volume of the NeoSAL™ device is 0.7 mL, gravimetric work shows that OF can be collected in excess of the stated collection volume and drug recoveries for the amphetamine drugs from the device assessed were acceptable.