Monitoring of chronic Cannabis abuse: An LC-MS/MS method for hair analysis

► First method analysing simultaneously THC and THC-COOH in hair by LC-MS/MS. ► Hair is the only biological matrix that allows a retrospective monitoring. ► Method fully validated on standard solutions and “blank” hair samples. ► Application to real hair samples from chronic Cannabis abusers. ► Method suitability for forensic cases, workplace testing and legal surveys.