This work demonstrates the use of disposable pipette extraction (DPX) as a fast and automated sample preparation technique for the determination of barbiturates and 11-nor-9-carboxy- 9-THC (COOH-THC) in urine. Using a GERSTEL MultiPurpose Sampler (MPS) with DPX option coupled to an Agilent 6460 LC-MS/MS instrument, 8 barbiturates and COOH-THC were extracted and their concentrations determined. The resulting average cycle time of 7 min/sample, including just-in-time sample preparation, enabled high throughput screening.
Validation results show that the automated DPX-LC/MS/MS screening method provides adequate sensitivity for all analytes and corresponding internal standards that were monitored. Lower limits of quantitation (LLOQ) were found to be 100 ng/mL for the barbiturates and 10 ng/mL for COOH-THC and % CVs were below 10 % in most cases.
