Direct-heating headspace solid-phase microextraction for the screening of illicit drugs

Illicit drugs, such as synthetic cannabinoids and cathinones, are produced in various forms, including volatile liquids, water-soluble liquids, powders and herbs. We developed a simple screening method to analyze illicit drugs in any form. In this method, a raw sample was directly placed in a solid-phase microextraction (SPME) vial, and an SPME fiber was inserted in the headspace of the vial. Illicit drugs were adsorbed onto the fiber at room temperature or by heating the vial directly. For samples that required heating, the vials were placed in a vessel filled with alumina balls (0.5 mm diameter) and heated on a hot plate. The inner-bottom temperature of the vial was measured over time, and the optimum adsorption times of the drugs were identified. After adsorption, the fiber was directly injected to the injection inlet of a gas chromatography–mass spectrometry instrument for desorption and analysis. For volatile liquids, such as nitrite esters, an adsorption time of 5 s at room temperature was sufficient. For water-soluble liquids containing compounds, such as phenethylamines and cathinones, an adsorption time of 30 s with heating was used. Furthermore, for refractory herbs, including tryptamines and synthetic cannabinoids, an adsorption time of 7 min with heating was used. Actual case samples in various forms were also tested using this method. This analysis method, called direct-heating headspace SPME, was effective for primary screening to quickly identify a number of illicit drugs in various forms.