Online Automated Solid Phase Extraction and Determination of Drugs of Abuse in Oral Fluid Samples using a Robotic Autosampler and LC-MS/MS

The determination of drugs of abuse in oral fluid has become increasingly popular due to several advantages associated with sample collection compared to other biological matrices. Oral fluid collection is noninvasive, can be performed under directly observed conditions, and reduces privacy concerns commonly associated with urine collection. In addition, the simplicity of oral fluid collection minimizes opportunities for sample adulteration, thereby improving confidence in the validity of analytical results. Following collection, the oral fluid collection devices used are typically placed into storage tubes containing stabilization buffer, allowing samples to be safely transported or stored prior to laboratory testing.

Although the stabilization buffer is essential for preserving analyte integrity within oral fluid samples, it also introduces analytical challenges during subsequent LC-MS/MS determination. The dilution of the sample within the buffer, combined with the presence of matrix components, can contribute to ion suppression and reduced analytical sensitivity. As a result, oral fluid samples are typically subjected to solid phase extraction (SPE) prior to analysis to remove interfering matrix components and concentrate analytes present at low concentrations. Automation of the SPE workflow offers significant advantages by improving extraction reproducibility, minimizing analyst-to-analyst variability, reducing manual sample handling, and increasing laboratory throughput. This report describes the development and implementation of an automated SPE workflow for the extraction and determination of drugs of abuse in oral fluid samples prior to LC-MS/MS determination.