Isoconversional thermal and pyrolytic GC–MS analysis of street samples of hashish

Abstract

Thermal decomposition of hashish, a widely used illicit drug, was studied by isoconversional and pyrolytic GC–MS analysis. An accurate value of activation energy was determined by the B-1.92 method, which was used to determine degradation mechanism, impact of destruction by incineration of the drug on environment. The thermograms exhibited a weight loss of 11–19% from ambient to 463K due to moisture content. Major degradation occurred in the range 463–643K. The average activation energy was found to be ∼121kJmol−1 that suggested rapid volatilization of the material in the temperature range. The variation of activation energy with conversion suggested a multistep degradation of the samples. The mechanism of degradation was found to be a second order decomposition representing an exothermic chemical change. The residue at 1073K 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–MS analysis identified cannabidiol, limonene, β-caryophyllene and pyrolytic products of acetaminophen and dehydrophenacetin as the major decomposition products. This study shows that the incineration process does not completely destroy the drug, rather it throws large quantities of drug-related toxic substances into the environment. The pyrolysis GC–MS showed that the characteristic peak due to cannabidiol can be used as a signature of the drug in biological samples.