Abstract A fully automated procedure using alkaline hy- drolysis and headspace solid-phase microextraction (HS- SPME), followed by on-fiber derivatization and gas chro- matographic–mass spectrometric (GC–MS) detection has been developed for determination of cannabinoids in hemp food samples. After addition of a deuterated internal stan- dard, the sample was hydrolyzed with sodium hydroxide and submitted to direct HS-SPME. After absorption of analytes for on-fiber derivatization, the fiber was placed directly into the headspace of a second vial containing N-methyl-N- trimethylsilyltrifluoroacetamide (MSTFA), before GC–MS analysis. Linearity was good for Δ 9 -tetrahydrocannabinol (THC), cannabidiol, and cannabinol; regression coefficients were greater than 0.99. Depending on the characteristics of the matrix the detection limits obtained ranged between 0.01 and 0.17 mg kg –1 and the precision between 0.4 and 11.8%. In comparison with conventional liquid–liquid ex- traction this automated HS-SPME–GC–MS procedure is substantially faster. It is easy to perform, solvent-free, and sample quantities are minimal, yet it maintains the same sensitivity and reproducibility. The applicability was demon- strated by analysis of 30 hemp food samples. Cannabinoids were detected in all of the samples and it was possible to differentiate between drug-type and fiber-type Cannabis sativa L. In comparison with other studies relatively low THC concentrations between 0.01 and 15.53 mg kg –1 were determined. Keywords Cannabinoids · Hemp food · Tetrahydrocannabinol (THC) · Solid-phase microextraction (SPME) · Gas chromatography (GC) · Mass spectrometry (MS) Introduction Cannabinoids are a group of terpenophenolic compounds found only in the hemp plant Cannabis sativa L. (Canna- baceae) [1]. Δ 9 -Tetrahydrocannabinol (THC) is the psy- choactive component; other major constituents are canna- bidiol (CBD) and cannabinol (CBN) (Fig. 1). On the basis of THC content cannabis plants are divided into fiber-type and drug-type plants. The ratio (THC+CBN)/CBD has been proposed for distinguishing between the phenotypes of cannabis plants [2, 3, 4]; if the ratio obtained is greater than 1, the cannabis plant is classified as drug-type; if it is less than 1, it is a fiber-type. After the legalization of fiber-hemp cultivation, hemp food products, mostly sold in esoteric stores, were eaten, because of supposed psychoactive properties associated with a potential THC content. Positive drug tests for mar- ijuana use have been reported after ingestion of hempseed oil [5, 6, 7, 8, 9, 10] and other hemp foods [11, 12]. Intox- ication has also been reported [13]. Since the mid 1990s, hemp food has gradually expanded into the natural prod- uct market and is increasingly found in natural food stores sold for nutritional and health benefits [14, 15]. A wide variety of hemp-based products is available, including hemp leaves (tea), hemp seed and seed derivatives, oil, flour, beverages (beer, lemonade), and cosmetic products. The upper THC limit for industrial hemp varieties grown for fiber and seeds and licensed for farming in the Euro- pean Union (EU) has gradually been lowered from 0.5% (w/w) (1984) to 0.2% (w/w) (since 2002) [16]. In Switzer- land, all cannabis plant types can be cultivated legally, but THC limits for hemp food were established [17]. The Ger- man health authorities estimated a provisional tolerable THC intake of 1–2 μg kg –1 day –1 [18], which resulted in pre- cautionary guidance values for THC in hemp-containing foods [19]. Hemp food products, even from fiber-type cannabis va- rieties, generally contain measurable amounts of THC. Pre- vious analyses of hemp seed oil have revealed a wide range of THC concentrations between 11.5–117.5 mg kg –1 [20] and 7–150 mg kg –1 [12]. Because of the origin of the seeds Dirk W. Lachenmeier · Lars Kroener · Frank Musshoff · Burkhard Madea Determination of cannabinoids in hemp food products by use of headspace solid-phase microextraction and gas chromatography–mass spectrometry Anal Bioanal Chem (2004) 378 : 183–189 DOI 10.1007/s00216-003-2268-4 Received: 31 July 2003 / Revised: 5 September 2003 / Accepted: 12 September 2003 / Published online: 4 November 2003 ORIGINAL PAPER D. W. Lachenmeier (✉) · L. Kroener · F. Musshoff · B. Madea Institut für Rechtsmedizin, Rheinische Friedrich-Wilhelms-Universität, Stiftsplatz 12, 53111 Bonn, Germany e-mail: Lachenmeier@web.de Present address: D. W. Lachenmeier Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weißenburger Str. 3, 76187 Karlsruhe, Germany © Springer-Verlag 2003