Abstract
A technique capable of determining both Δ9-tetrahydrocannabinol and 11-hydroxy-Δ9-tetrahydrocannabinol is described. The method is based on the reactivity of the phenolic functionality common to both compounds, and is sensitive to 5 ng of Δ9-tetrahydrocannabinol and 1 ng of 11-hydroxy-Δ9-tetrahydrocannabinol per ml of plasma.