THC-COOH DETERMINATION IN HAIR WITH LC/MS/MS: A CHALLENGING REQUEST

Význam tématu

Analysis of 11-nor-9-carboxy-△9-tetrahydrocannabinol (THC-COOH) in hair provides a reliable record of long-term cannabis consumption and supports forensic investigations, workplace drug testing, and clinical monitoring by offering an extended detection window and high analyte stability in the hair matrix.

Cíle a přehled studie / článku

The study describes development and validation of a sensitive LC/MS/MS method capable of quantifying THC-COOH at levels as low as 0.2 pg/mg hair, meeting the Society of Hair Testing confirmation cutoff. The workflow integrates simple sample preparation, solid-phase extraction, and tandem mass spectrometry for trace-level determination.

Použitá metodika a instrumentace

• Sample preparation: Hair decontamination with dichloromethane and methanol, cutting into 1–2 mm segments, alkaline hydrolysis (1 M NaOH, 70 °C, 30 min), centrifugation, SPE clean-up using Bond Elut Certify cartridges.
• Internal standard: THC-COOH-D3 spiked at 1.25 pg/mg.
• Chromatography: Agilent 1290 Infinity II LC with Zorbax Eclipse Plus C18 RRHD column (50 °C), mobile phases ammonium fluoride (A) and acetonitrile/methanol/isopropanol (B), flow rate 0.150 mL/min, injection volume 5 µL.
• Mass spectrometry: Agilent 6495 Triple Quadrupole MS, ESI Jet Stream in negative mode, MRM transitions for THC-COOH (343.2→299.0, 343.2→245.1, 343.2→191.0) and THC-COOH-D3 (346.2→194.0).
• Software: MassHunter acquisition, qualitative and quantitative analysis modules.

Hlavní výsledky a diskuse

The method achieved clear chromatography with an 11 min run time. Linearity over 0.2–10 pg/mg hair showed R2 = 0.9952. The lower confirmation limit was established at 0.2 pg/mg. Intraday precision (n=8) at 0.2 pg/mg and 1.0 pg/mg exhibited RSDs of 8 % and 9 %, respectively, with bias within ±2.5 %. Minor matrix interferences were noted in one qualifier transition at the lowest level but did not compromise quantification. Authentic samples from cannabis users yielded 1.5 pg/mg and 0.98 pg/mg of THC-COOH.

Přínosy a praktické využití metody

• Enables forensic confirmation of cannabis exposure at trace levels aligned with international guidelines.
• Streamlined sample preparation with efficient SPE clean-up to reduce matrix effects.
• Applicable to criminal investigations, drug treatment monitoring, and workplace testing.

Budoucí trendy a možnosti využití

Future directions include adoption of high-resolution mass spectrometry to enhance selectivity, automation of sample processing for higher throughput, expansion to additional cannabinoids and metabolites, and miniaturized or ambient ionization techniques to shorten analysis time and reduce solvent consumption.

Závěr

A robust UHPLC-MS/MS method was validated for quantifying THC-COOH in hair down to 0.2 pg/mg, fulfilling stringent forensic requirements with high sensitivity, precision, and real-sample applicability.

Reference

1. Cooper GAA, Kronstrand R, Kintz P. Society of Hair Testing guidelines for drug testing in hair. Forensic Science International. 2012;218:20–24.