Analysis of the California List of Pesticides and Mycotoxins in Edibles

Description

The use of cannabis for medicinal and/or recreational purposes has become legal in several states. Regulations that permit the use of different forms of cannabis demand effective and reliable analytical strategies to ensure the safety of cannabis users. 
 
Pesticide content is one of the main parameters tested in cannabis and cannabis-derived products due to the risks that these compounds pose for human health. However, the main challenges associated with pesticide testing rely on the broad range of physicochemical properties of these compounds, the low action levels requested by the regulations, and the complexity and diversity of matrices to be analyzed.  
 
In this poster video, we’re going to present sample preparation and instrumental strategies for the accurate quantitation of the California list of pesticides and mycotoxins in cannabis products.

Additional Resources

• Download a PDF of the full presentation

Transcript

Hi, my name is Nathaly Reyes, and I work as an applications scientist at Restek Corporation in the LC solutions department. My poster is entitled “Analysis of the California List of Pesticides and Mycotoxins in Edibles,” and it describes a simple yet effective workflow for the analysis of these analytes in cannabis goods. For this work, brownies were chosen as model matrix.

First, it is important to emphasize that legalization of cannabis for recreational and medical purposes demands accurate, reliable analytical methods to assess the quality and safety of any cannabis-derived good. Developing effective methods requires careful consideration of analyte properties and matrix effects, and testing is further complicated because requirements vary by country and state for different product types. Among the various commercially available cannabis products, edibles constitute one of the most popular categories. Edibles encompass a broad variety of goods, including several types of beverages, chocolates, baked goods, candy, among others. Currently, the state of California demands the analysis of an extensive list of pesticides and mycotoxins not only in cannabis flower but also in cannabis-derived goods. For this reason, methods capable of tackling challenges for different matrices are highly desired.

In the methodology we are proposing, pulverized brownie (0.5 g) was fortified with analytes at concentrations from 5-700 ng/g and with internal standards at 200 ng/g. For the extraction, 1.5 mL of acetonitrile with 1% acetic acid was added to the sample. Sample was vortexed and sonicated for 5 minutes, and then the supernatant was passed through a C18 SPE cartridge. An additional 1.5 mL of solvent was added to the sample, and then the sample was vortexed again. Supernatant was passed through the same cartridge.

For LC-MS/MS analysis, 750 µL of supernatant was mixed with 250 µL of water. Only 2 µL were injected in the system. For the analysis of GC-amenable pesticides, the remaining supernatant was transferred to a dSPE tube containing magnesium sulfate and PSA. After vortexing and centrifuging, 500 µL of extract was mixed with 500 µL of solvent. One microliter of extract was then injected in the GC-MS/MS system.

LC-MS/MS analysis of our extracts was performed using our Raptor ARC-18 column and a Shimadzu LCMS-8060. General instrument conditions are provided in Table 1. GC-MS/MS analysis was conducted using an Rxi-5ms analytical column and a Thermo Scientific TSQ 8000 triple quad GC-MS/MS. Instrument conditions are provided in Table 2.

Note that it was important to use a single taper inlet liner with wool for this application. The wool packing enhances vaporization and mixing with the carrier gas for better reproducibility, and the taper at the bottom of the liner funnels analytes onto the column, reducing the potential for interactions with the inlet seal. In addition, a 10-minute hold time was used at the end of each run in order to ensure that compounds would not carry over and interfere with subsequent analyses.

Figures 2 and 3 show chromatograms obtained for LC-and GC-amenable pesticides and mycotoxins in matrix, respectively. As can be seen in Table 3, our workflow showed a satisfactory performance for the simultaneous analysis of the California list of pesticides and mycotoxins in brownies with only 3.5 mL of solvent consumed per sample. Multiple experimental parameters were evaluated, and valuable lessons were learned over the course of the sample preparation optimization. For instance, it was found that the addition of acetic acid to the extraction solvent enhanced the recovery of daminozide, spiroxamine, and ochratoxin A. In addition, an increase in recovery values of about 20% were observed for several analytes by performing a two-step extraction compared to a typical single-step extraction.  The use of internal standards and matrix-matched calibration were imperative to obtain a reliable methodology. Extracts showed acceptable stability even after 48 hours in the LC autosampler.

Overall, the proposed methodology provided excellent results in terms of linearity, accuracy, precision, and limits of quantitation.

Thank you for watching this video, if you would like more information about this work, please check the links below.