interference contribution to peak area) and the Calculated Concentrations (from the Calibration Curve) showing larger
deviations from the Certified Concentrations.
The final thing that needs to be done is relate all of this back to ppm values in the original marijuana sample based on the amount
extracted, the QuEChERS solvent volume, and the spike amount. And, I’m basing the numbers on “100% extraction recovery”
(actual recovery needs to be verified on “incurred” residues in cannabis). When that is done, we’ve been looking at 1000, 500,
250, 100, 50, 25, 10, 5, and 2.5 ppm, bifenazate in marijuana. The workable range though is likely from 1000 to 10 ppm, and
that is ONLY for this particular sample, as another cannabis might contain compounds that interfere with bifenazate under these
GC conditions.
In conclusion, the method presented here for bifenazate in marijuana will likely allow only gross-level screening work, which
may still be of value to medical marijuana laboratories. GC-MS with selected ion monitoring should allow a better
determination, certainly one that is better for confirmation over FID, when using the same QuEChERS extraction technique.
Medical Marijuana « ChromaBLOGraphy: Restek's Chromatography Blog
16 of 23
02/08/2014 5:38 P
