I recommend examining the following conditions when selecting a cannabis testing lab.
1. Check their website regarding instrumentation used for each step. A reputable lab will list the analytical instrumentation used for each analysis and be proud to give a virtual tour of the lab.
Make sure that the following are being done for each type of test
Potency – HPLC is what most labs use due to the instruments relative low cost, easy maintenance, and easy operation. A lab might go above and beyond and use a more accurate LC-MS/MS for edibles or other matrix heavy samples in addition to potency of flower and concentrates. I have not seen a lab that offers GC-MS testing, but this is also possible, although it is far from the optimal way, since all carboxylic acid cannabinoids (THCa, CBDa, etc) will automatically be decarboxylated in the inlet.
Terpenes – This is one area that has the most diversity in method creation. GC is used with either direct liquid injection or headspace analysis and use either a mass spectrometry detector (MS) or a Flame Ionization Detector (FID). These techniques are abbreviated HS-GC-MS, HS-GC-FID, GC-MS, or GC-FID. It is my opinion that headspace sampling is not that important, but it adds to the keeping the instrument clean, which limits consumable cost and downtime. GC-MS is superior to GC-FID due to its ability to unequivocally identify the terpene/terpenoid based on retention time and mass spectrum. It costs more and requires more experience to operate and maintain than an FID instrument. You might see some labs try to use their LC-MS/MS system to quantify terpenes as well, although this is not optimal for volatile terpenes and the number of terpenes in the test menu for this technique is typically limited.
Pesticides – LC-MS/MS is what every lab uses. I don’t think I have ever seen a lab not use LC-MS/MS for pesticides. GC-MS/MS might also be used in addition to LC-MS/MS for pesticides that do not ionize well with the ESI source used in LC based instruments. Oklahoma’s required pesticide list is so small that a tandem GC-MS is not needed
Metals – ICP-MS is the gold standard to see the sub ppm limits of detection that most states require.
Microbials – A lab that goes above a beyond will utilize qPCR, while most small labs will probably just be plating petri dishes because it is much cheaper. I would highly recommend finding a lab that used qPCR since that is a much more accurate way of checking for microbials.
Mycotoxins – Mycotoxins are detected with an LC-MS/MS system along with cannabinoids and pesticides. I have seen some labs use a fluorometer for mycotoxin testing, although I have not reviewed this technique enough to make any comments about it. LC mass spec is tpyically the best because of its high sensitivity and specificity of being about to take into account multiple parameters for compound identification.
2. How big is their analyte test menu?
Some labs don’t separate delta 8 and delta 9 THC in their chromatograms. Look for a lab that is able to give you delta 8 THC, delta 9 THC, along with other relevant cannabinoids, THCA, CBDA, CBD, CBG, CBN, THCV, and CBDV. Delta 8 THC is not prevalent in flower, however, there a sometimes an uncharacteristically high amount in some distillates depending on how the distillate is prepared.
Get quotes from different sources and obtain the best service to cost ratio.
4. Check the experience and background of the lab staff.
Some labs simply just have a method set up by a third party and have technicians that have minimal or even no experience in analytical techniques such as LC-MS, GC-MS, or ICP-MS since the instrumentation cost is too high for routine usage in an academic setting. Some labs might even staff a PhD chemist, but this person might not have experience with the analytical techniques used and the nuances associated with them. However, for the most part, this doesn’t really matter as long as SOPs are followed without deviation and there is a scientifically validated method that was setup up properly with the assistance of an expert consultant who has a significant amount of cannabis testing experience.
5. Ask questions
What is their typical turnaround time? Is this turnaround time guaranteed? How did they come up with their methods? Did they make all of them in-house (which is a very difficult and time consuming process that is subject to error) or did they hire an outside consultant from a pre-existing cannabis testing lab in a different state to help explain all their mistakes when starting out.