Polyamide-coated wooden tips coupled to direct infusion mass spectrometry, a high throughput alternative for the determination of methadone, cocaine and methamphetamine in oral fluid

The use of natural materials as substrates or sorptive phases is a key trend in sample preparation. In this article, the porous structure of wooden tips (WTs) is exploited to achieve their simple modification with a polyamide by the dip-coating technique. Nylon 6, which combines hydrophobic interactions and H-bonding, is used as coating for the extraction of three drugs of abuse (namely, methadone, cocaine and methamphetamine) from oral fluid samples. A straightforward analytical method, which is based on the direct combination of WTs extraction and mass spectrometry by the direct infusion of the extracts, is proposed. The simultaneous extraction of multiple samples and the rapid analysis run (2 min) provides a high sample throughput. Working under the optimal conditions, the method presents limits of detection of 1.5 mu g L-1 and linearity up to 100 mu g L-1 for methamphetamine and 250 mu g L-1 for methadone and cocaine, permitting for example the confirmation of the drug presence in forensic studies. The precision values, expressed as relative standard deviations (RSD), were better than 9.1, 12.6 and 18.2% for methadone, cocaine and methamphetamine respectively. The accuracy, calculated as relative recovery, was in the range from 86 to 103%.

Automated summary

The use of natural materials such as wooden tips with a porous structure coated with nylon 6 is proposed for the extraction of drugs of abuse from oral fluid samples. This method allows for simultaneous extraction of multiple samples and provides high sample throughput with detection limits of 1.5 μg L-1 for methamphetamine. Precision values were better than 9.1%, 12.6%, and 18.2% for methadone, cocaine, and methamphetamine respectively, with an accuracy range from 86% to 103%.