Identification of Cannabinoids in Baked Goods by UHPLC–MS

Jason R. Stenzel¹ and Guifeng Jiang,²

¹Washington State Patrol — Crime Laboratory Division, Cheney, Washington, USA,

² Thermo Fisher Scientific Inc., San Jose, California, USA.

Goal: Positively identify trace amounts of cannabinoids in a complex food matrix quickly, with minimal sample preparation and no chemical derivatization.

Introduction

Marijuana is the most common illegal drug in the US and each year US law enforcement agencies seize more than two million pounds of marijuana in various forms. Seized evidence submitted to forensic laboratories is screened for marijuana. Presumptive positive results are confirmed by using gas chromatography–mass spectrometry (GC–MS) to positively identify cannabinoids. This traditional approach works fairly well for leaf marijuana, hashish, hash oil and residue collected from smoking paraphernalia.

GC–MS is less useful for confirming the presence of marijuana in complex food matrices such as baked goods. Simple sample preparation procedures using methanol or methylene chloride coextract many small molecules found in baked goods that can coelute with the target cannabinoids. Cholesterol, fatty acids and caffeine can contaminate the gas chromatograph, forcing the analyst to clean the instrument and rerun all subsequent samples.

An alternative method to positively identify marijuana cannabinoids in complex food matrices is to use ultra high performance liquid chromatography with mass spectrometry detection (UHPLC–MS). UHPLC–MS offers a three-fold benefit compared to GC–MS; simpler sample preparation, no derivatization and less instrument clean-up time.

Experimental Conditions

Brownie and cookie samples were obtained from evidence archived after adjudication. 2 mL methanol was added to 25 mg of baked-good material. This mixture was vortexed and the supernatant was filtered through a cotton-plugged Pasteur pipette. The filtrate was diluted 50-fold with methanol prior to analysis. Chromatographic analyses were performed using the Accela UHPLC system (Thermo Fisher Scientific, San Jose, California, USA). MS analysis was performed on a MSQ Plus single quadrupole LC–MS detector with Xcalibur 2.05 (Thermo Fisher Scientific, San Jose, California, USA). For the complete chromatographic and mass spectrometer conditions please refer to the complete application note.

Results

The cannabinoid standards elute with good resolution at 4.1 min (cannabidiol), 5.1 min (THC) and 5.4 min (cannabinol). The cannabinoids were detected by using full scans (50–500 m/z) of the single quadrupole mass spectrometer and the extracted ion chromatograms from m/z 310.5–311.5 + 314.5–315.5 are displayed in Figure 1(a). Molecular ions of each compound (m/z 315 for cannabidiol and THC and m/z 311 for cannabinol) are observed.

Figure 1

The brownie sample, which was taken from an adjudicated case and was known to contain THC, tested positive for THC [Figure 1(b)], demonstrating that the sample preparation required for this LC–MS method is simpler, faster and requires less sample than the GC–MS method employed for the original casework.

After 10 years in the forensic laboratory's training vault, cannabinoids in the cookie sample had degraded significantly, but by increasing the sample injection from 2 μL to 10 μL, THC was detected with good signal-to-noise [Figure 1(c)].

Conclusion

Cannabinoids in baked goods can be identified using UHPLC–MS with minimal sample preparation. The preparation time (10 min) and run time (8 min) make this a very efficient analytical method.

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