Analytical Instrument Documents

EXPERIMENTAL

Dried Cannabis sativa flower buds for recreational use were purchased from a local dispensary. Approximately 1 gram of flower was extracted into 10 mL of 90:10 acetonitrile:dimethylacetamide by sonication for 15 minutes. The extract was centrifuged at approximately 2500 rpm for 10 minutes, followed by 10X dilution. One mL of the diluted extract was put through a dSPE cleanup step using Restek Q-sep QuEChERS dSPE Tubes (AOAC 2007.01 method⁴, PN# 26125) and following the provided dSPE instructions. The supernatant was used as the matrix for each sample. Each spiked sample was created by adding 10 μL of prepared pesticide standard to 90 μL of the matrix. Samples were analyzed on the JMS-TQ4000GC using the parameters and SRM channels outlined in Tables 1 - 3 below. Optimal product- and precursor-ion pairs and optimized collision energies for each pesticide were determined using built-in SRM optimization tools. Each sample was run in triplicate with the exception of the 1 ppb samples for which 8 replicates were done to calculate the instrument detection limit (IDL) where possible.

RESULTS

Figure 1 shows the total ion current chromatogram (TICC) with labeled peaks, and Figure 2 shows several selected SRM chromatograms.  Table 4 lists the data acquired for 46 pesticides analyzed by GC-MS/MS analysis. There were 41 pesticides observed at 1 ppb or less, which translates to 10 ppb on the plant. The IDL and %CV were not calculated for samples that could not be observed at 1 ppb.  For samples with isomers (e.g., chlordane), the best performing isomer was used for reporting.  All samples below showed good linearity, even up to 100 ppb.  Example calibration curves are shown in Figure 3.  Although some matrix effects were observed, system performance was generally good with very few pesticides affected by matrix interference.

CONCLUSIONS

The JMS-TQ4000GC is an excellent platform for fast, sensitive analysis of a wide range of pesticides in Cannabis matrix. Using built-in SRM optimization tools, optimal ion transitions and collision energies for each pesticide were determined in the presence of the matrix. The SRM method provided high sensitivity and selectivity, and reduced matrix effects without a complicated extraction method.  Forty-one pesticides were observed at one ppb or lower with good linearity, which translates to ten ppb on the flower and is sufficient to meet the action limits of jurisdictions of interest. 

REFERENCES

1. United States Drug Enforcement Administration. The Controlled Substances Act https://www.dea.gov/controlled-substances-act (accessed Mar 19, 2020).
2. Health Canada. Mandatory cannabis testing for pesticide active ingredients - List and limits https://www.canada.ca/en/public-health/services/publications/drugs-health-products/cannabis-testing-pesticide-list-limits.html (accessed Mar 19, 2020).
3. Dodson, L.; Laprade, N. M. The Natalie M. Laprade Maryland Medical Cannabis Commission’s (MMCC) Technical Authority for Medical Cannabis Testing; 2019.
4. Official Methods of Analysis. Pesticide Residues in Foods by Acetonitrile Extraction and Partitioning with Magnesium Sulfate. Association of Official Agricultural Chemists: 2007.01.

Table 1. Gas Chromatograph parameters.

Figure 1. TIC chromatogram.

Figure 2. Selected SRM chromatograms.

Figure 3. Selected calibrations curves.

Table 4. Performance data for tested pesticides.