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Volume 36, Issue 2
Cannabis testing laboratories have the challenge of removing a variety of unwanted matrix components from plant material prior to running extracts on their LC–MS/MS or GC–MS. The complexity of the cannabis plant presents additional analytical challenges that do not need to be accounted for in other agricultural products. While novel methods have been developed for the removal of chlorophyll, few sample preparation methods, if any, have been devoted to removal of other colored pigments from other popular cannabis strains.
Figure 1: Cannabis strains used (clockwise from top left): Agent Orange, Tahoe OG, Blue Skunk, Grand Daddy, and Grape Drink.
a) Add 1 g of cannabis + 10 mL H2O
b) Vortex briefly and hydrate for 10 min.
c) Add 10 mL ACN + 2% formic acid + the QuEChERS extraction salts from the Mylar pouch (ECMSSC50CT-MP) to the 50-mL tube, and shake vigorously for 1 min manually or using a Spex 2010 Geno-Grinder at 1000 strokes/min.
d) Centrifuge at ≥3000 rcf for 5 min.
e) Transfer 1 mL supernatant to SpinFiltr® dSPE cleanup tube.
f) Vortex for 30 s and centrifuge at ≥3000 rcf for 2 min.
g) Transfer purified and filtered extract into autosampler vial for analysis.
Figure 2: Cannabis samples following hydration. Left: Grape Drink Strain, right: Agent Orange Strain.
A blend of MgSO4, C18, PSA, and Chlorofiltr® allowed for the most effective sample clean up, without loss of pesticides and mycotoxins, for all cannabis samples tested. Average recovery of the 48 pesticides and four mycotoxins using the selected dSPE blend was 75.6% where as the average recovery when including GCB instead of Chlorofiltr® was 67.6%. Regardless of the sample's original pigmentation, this blend successfully removed both chlorophyll and purple hues from all strains tested. The other six dSPE blends evaluated were unable to provide the sample clean up needed or had previously demonstrated to be detrimental to the recovery of pesticides routinely analyzed for in cannabis.
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