Automated Extraction of 11-nor-9-Carboxy-Δ9- THC from Hydrolyzed Urine Using ISOLUTE® SLE+ Prior to GC/MS Analysis

Significance of the topic

Detection of 11-nor-9-carboxy-Δ9-THC in urine is critical for workplace drug testing, forensic toxicology and monitoring compliance. Traditional liquid-liquid extraction methods can be time-consuming and prone to variability. Automated supported liquid extraction using ISOLUTE SLE+ columns offers a streamlined approach with improved reproducibility, reduced manual handling and enhanced throughput.

Objectives and Study Overview

This study presents a fully automated sample preparation workflow using the Biotage Extrahera system and ISOLUTE SLE+ columns to extract carboxy-THC from hydrolyzed urine samples. The primary goals were to achieve high analyte recovery, low relative standard deviation, and a limit of quantitation below regulatory cutoffs.

Methodology and Instrumentation

Sample pre-treatment involved spiking urine with a deuterated internal standard, base hydrolysis at 60 °C, neutralization with acetic acid, followed by loading onto ISOLUTE SLE+ columns. Automated extraction employed two sequential washes with hexane/ethyl acetate (50:50 v/v) under gravity and vacuum. Eluates were evaporated and derivatized with BSTFA:TMCS before GC-MS analysis. Instrumental analysis was carried out on an Agilent 7890A gas chromatograph coupled to a 5975C mass selective detector using an Rxi-5ms column and selected ion monitoring of characteristic ions for THC-COOH and THC-COOH-D9.

Main Results and Discussion

The optimized protocol delivered mean recoveries of 85% for carboxy-THC and 82% for the deuterated standard with RSD values below 10%. Calibration curves were linear between 5 and 100 ng/mL (r2 > 0.999), indicating an inferred limit of quantitation between 5 and 10 ng/mL. The automated method processed 24 samples in approximately 35 minutes, demonstrating high throughput and consistency.

Benefits and Practical Applications

• High analyte recovery and reproducibility
• Reduced solvent consumption and no emulsion formation
• Automated, high-throughput processing suitable for clinical and forensic laboratories
• Compliance with SAMHSA and EWDTS confirmation requirements

Future trends and potential applications

Integration of automated SLE workflows with LC-MS/MS platforms, expansion to other drug metabolites, miniaturization of sorbent formats, and use of greener solvents may further enhance bioanalytical efficiency and sustainability.

Conclusion

The automated ISOLUTE SLE+ extraction protocol provides a robust, efficient and reproducible approach for quantifying carboxy-THC in urine, suitable for high-throughput drug testing environments.

References

1. Biotage. Automated Extraction of 11-nor-9-carboxy-Δ9-THC from Hydrolyzed Urine Using ISOLUTE SLE+. Application Note AN892; 2018.