Isoconversional thermal and pyrolytic GC–MS analysis of streetsamples of hashish

Abstract

Thermal decomposition of hashish, a widely used illicit drug, was studied by isoconversional and pyrolyticGC–MS analysis. An accurate value of activation energy was determined by the B-1.92 method, whichwas used to determine degradation mechanism, impact of destruction by incineration of the drug onenvironment. The thermograms exhibited a weight loss of 11–19% from ambient to 463 K due to moisturecontent. Major degradation occurred in the range 463–643 K. The average activation energy was foundto be ∼121 kJ mol−1that suggested rapid volatilization of the material in the temperature range. Thevariation of activation energy with conversion suggested a multistep degradation of the samples. Themechanism of degradation was found to be a second order decomposition representing an exothermicchemical change. The residue at 1073 K was analyzed by SEM-EDS and found to contain C, O, P, S, K,Mg, Ca, Al and Si to various extents; C and O were present in substantial amounts. Pyrolytic GC–MSanalysis identified cannabidiol, limonene, -caryophyllene and pyrolytic products of acetaminophen anddehydrophenacetin as the major decomposition products. This study shows that the incineration processdoes not completely destroy the drug, rather it throws large quantities of drug-related toxic substancesinto the environment. The pyrolysis GC–MS showed that the characteristic peak due to cannabidiol canbe used as a signature of the drug in biological samples.