Evolution of a Multi-Source, Bipolar HPLC/MS/MS/MS Method to Analyze Pesticide and Mycotoxin Residues in Cannabis Matrices: A Tale of Three States
Soren N. Eustis, Ph.D. – MCR Labs
Introduction:
The lack of a nationwide standard for cannabis testing presents many challenges. Chief among them is the wide variation in the regulated analytes and their acceptable level from state to state. This work examines the development of three separate methods designed to satisfy the mandatory testing requirements for pesticides and toxins in cannabis products in Massachusetts, Maine, and New York.
Methods:
Cannabis flower and concentrate are extracted using acetonitrile with mechanical agitation. The resulting slurry or solution is centrifuged, and a portion of the supernatant is collected. These aliquots are chilled at -40 ℃ for two hours to minimize cannabinoid interferences and centrifuged again. The resulting solution is Separated by HPLC (Phenomenex Luna C18) and introduced to a triple quadrupole mass spectrometer (SciEx 6500+). Depending on the analyte list, the samples are ionized via electrospray ionization (ESI) or atmospheric pressure chemical ionization (APCI). Scheduled multiple reaction monitoring (sMRM) is used to strategically maximize the fragmentation of parent ions and allow for monitoring 60+ individual analytes per run.
Results:
Massachusetts
Massachusetts has a required list of nine required pesticides and four required toxins. Figure XX. shows a representative chromatogram. In this method, all thirteen analytes are able to be run at once, using the ESI source in positive ion mode. Runtime = 9 minutes.
Maine
The required list for Maine jumps significantly when compared to that of Massachusetts. A total of 59 pesticides are required to be analyzed (Figure XX). However, toxin testing is not required for a primary screen. This method uses the ESI source in a combined positive and negative mode. 58 analytes have sMRM segments that use positive mode, while methyl parathion has a negative sMRM segment (detecting the phenoxide fragment). The capabilities of the SciEx 6500+ mean that these two modes can be run simultaneously through ultrafast polarity switching. Runtime = 16 minutes.
New York
The most expansive analyte list belongs to New York State. Producers are required to test for 70 pesticides and four toxins (Fig XX). This increased number of analytes brings added complexity to the method. The NY method is a two-part analysis, owing to the nature of the analytes. First, 66 pesticides and the four toxins are analyzed using ESI(+). Following that analysis, the source is switched to an APCI probe. Four of our analytes are simply unable to be ionized using an ESI source due to their structures. The run is restarted using the APCI source and method, completing the analysis (Fig XX). Runtime = 16 minutes + cooldown + 16 minutes ~ 40+ minutes
Conclusion:
The lack of a standardized national testing framework results in vastly different analyte lists from state to state. This increases the complexity of method development and raises operational expenses, ultimately costing the testing consumer.
