Evaluation of Reduced Solvent Volume Solid-Phase Extraction Cartridges with Analysis by Gas Chromatography-Mass Spectrometry for Determination of 11-nor-9-Carboxy- 9-THC in Urine

A sensitive and reliable method was developed for the identification and quantitation of 11-nor-9-carboxy-delta 9-tetrahydrocannabinol (THCCOOH) in urine using a microbed solid-phase extraction (SPE) column. Extensive method validation is presented that evaluates the recovery, linearity, precision, limit of quantitation, limit of detection, and capacity of THCCOOH in urine extracts using CLEAN SCREEN reduced solvent volume (RSV) SPE columns followed by gas chromatographic-mass spectrometric analysis. The mean recovery of THCCOOH at concentrations of 2, 3, 5, 15, 50, and 150 ng/mL was found to be 91% with coefficients of variation of 7.3% or less. Linearity of the method ranged from 1.95 to 1000 ng/mL with sensitivity at 1 ng/mL for THCCOOH. The sorbent was found to retain at least 1000 ng/mL of THCCOOH with no analyte breakthrough using the described method. Reduction in both processing times and total solvent volume is shown. The RSV SPE columns showed excellent efficiency and performance while demonstrating recoveries, cleanliness, and dynamic ranges comparable with standard SPE products.