Detection and confirmation of urinary cannabinoids.

Area of Science:

• Forensic Toxicology
• Analytical Chemistry
• Pharmacology

Background:

• Accurate detection of cannabinoid metabolites in urine is crucial for drug testing.
• Various analytical methods exist, each with different sensitivities and specificities.
• Understanding the performance of these methods is essential for reliable results.

Purpose of the Study:

• To compare the performance of thin layer chromatography (TOXI-LAB) and two homogeneous immunoassays (EMIT-st, EMIT d.a.u.) for detecting tetrahydrocannabinol metabolites.
• To determine the reliability of combined analytical techniques for urinary cannabinoid analysis.

Main Methods:

• Analysis of 525 urine specimens using TOXI-LAB, EMIT-st, and EMIT d.a.u.
• Gas chromatography/mass spectrometry (GC/MS) was used to verify results for discrepant samples.

Main Results:

• All methods agreed on 283 negative specimens.
• EMIT-st detected 184 positive specimens, EMIT d.a.u. detected an additional 47, and TOXI-LAB confirmed all 231.
• Eleven specimens were positive by EMIT d.a.u. but negative by TOXI-LAB, with low concentrations of 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (average 7.4 ng/mL).

Conclusions:

• The TOXI-LAB procedure has a lower detection limit than EMIT d.a.u.
• Combining EMIT d.a.u. and TOXI-LAB provides reliable urinary cannabinoid analysis for concentrations above 25 ng/mL.
• This combined approach enhances the accuracy and reliability of drug testing.