Chromatography
Measurement of Pesticides in Cannabis sativa and Hemp Matrices Using a Gas Chromatograph-Triple Quadrupole Mass Spectrometer
Kirk R. Jensen*, A. John Dane, Robert B. Cody, and Koji Okuda *Corresponding author:
kjensen@jeol.com JEOL USA, Inc, Peabody, MA
An increase in legalisation of Cannabis sativa for recreational use and the advent of federal guidelines on hemp has created a need for sensitive analytical tools for pesticide measurement. The JEOL JMS-TQ4000GC triple-quadrupole mass spectrometer contains a unique short collision cell that provides sensitive and selective analysis of trace pesticides. To test the capabilities of the instrument for analysing pesticides in Cannabis and hemp matrices, dried fl ower buds from Cannabis sativa and hemp plants were extracted, spiked with pesticides, and then measured using selected reaction monitoring. Out of the 51 pesticides spiked into the samples, at least 45 were detected at 100 ppb or less and at least 35 of those at 1 ppb or less.
Introduction
Cannabis sativa is well known for its use as a recreational drug due the presence of the psychoactive compound tetrahydrocannabinol (THC), and has been listed as a Schedule 1 drug in the United States since the passage of the Controlled Substances Act of 1970 [1]. Hemp is a strain of Cannabis sativa that has multiple industrial uses including paper, plastics, woven goods, and even food. Hemp strains are defi ned by the US federal government as those that contain less than 0.3% THC [2]. Additionally, hemp strains typically contain more cannabidiol (CBD) [3], which was recently approved by the US Food and Drug Administration (FDA) to treat certain types of epilepsy [4], and is currently being investigated as a medical treatment for other affl ictions. With the recent surge in legalisation of recreational and medicinal use, and the advent of federal guidelines on the defi nition of hemp, there is a need for reliable analytical tools to meet the regulatory requirements for pesticide testing in Cannabis sativa. The US Environmental Protection Agency (EPA) sets tolerance limits for residual pesticides, and the FDA is responsible for enforcing those tolerances in agricultural products. Many pesticide limits are in the low ppb level, but the acceptable limits are compound dependent. A good example is permethrin in spinach, which has 20 ppm detection limits due to its low toxicity [5]. Because THC is still listed as a Schedule 1 drug, the FDA has not needed to set any pesticide requirements. As such, any limits have been left for individual jurisdictions (typically US state) to decide on which pesticides to regulate for Cannabis and to what level. Action limits for each pesticide vary between jurisdictions, but can be as low as 10 ppb [6,7,8].
Current methods for pesticide analysis in Cannabis are entirely based on LC-MS/MS and GC-MS/MS methods, with neither technology able to detect the full range of pesticides at regulated levels. The sample preparation methods and specifi c chromatography- MS methods vary from laboratory to laboratory and state to state depending on local regulatory requirements, though there does seem to be a general trend of using QuEChERS or QuEChERS-like methods (e.g., extraction into acetonitrile) and/or solid phase extraction (SPE) techniques. The AOAC Offi cial Method of Analysis 2007.01 has also been adopted by some laboratories. No specifi c LC-MS/MS or GC-MS/MS methods have been adopted by government regulatory agencies for Cannabis testing, however, the FDA has guidelines for both methods in the Pesticide Analytical Manual for testing other agricultural products [9]. Other reports also mention that both GC-MS and LC-MS are required to analyse a full range of pesticides [7].
Figure 2: Diagram showing how different ion accumulation times affect sensitivity in high-speed and high-sensitivity modes.
Figure 1: A diagram of the JMS-TQ4000GC triple quadrupole with its unique short collision cell.
The JEOL JMS-TQ4000GC triple-quadrupole gas chromatograph-tandem mass spectrometer (GC-MS/MS) system offers high speed and high sensitivity for quantitation of trace or residual pesticides. The JMS-TQ4000GC combines a unique short collision cell with JEOL’s patented ion accumulation and timed detection technology to provide high sensitivity and selectivity (Figure 1), as well as the fastest selected reaction monitoring (SRM) switching speed available (up to 1000 transitions per second). The short collision cell minimises the time that ions reside in q2, making it possible to carry out more SRM’s in a given timeframe (high-speed mode, Figure 2), with a maximum switching rate of 1000 SRMs per second. Ion accumulation in q2 combined with rapid ejection reduces interference ions and minimises ion loss when switching precursor/product ion pairs, thus increasing sensitivity.
INTERNATIONAL LABMATE - JULY 2020
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