Of all the labs I used in Oregon, I felt Pixis was hands down the most reliable, consistent, professional, and accurate. Typically I saw close agreement with their potency data and my own internal HPLC analyses. I think there is also a lot to be said that they had been doing analytical testing way way before weed became legal in Oregon. As their business is founded on food, water and agriculture testing, I felt they were less likely to introduce bias in testing with hopes of winning new customers over with inflated data. Any issues I had were resolved promptly and typically it was no bullshit, from sampling events, transferring samples, analysis, and turn around time. They also did all the tests in house - RSA, pesticides, potency etc. i much prefer to have a lab test everything themselves and not outsource testing - smaller labs are more inclined to outsource more expensive or complex testing like LC/GC-MS for pesticides.
I used Evio for a while also. Again results were accurate, with close agreement with my own in house HPLC potency analyses. They were very fast sampling. No bullshit. Professional. This was Evio in Portland.
Reference Labs was a complete joke.the worst I encountered in Oregon. The lab director more or less asked me what potency I want - and when given 3 one gram distillate samples from the same batch, the variation was all over the place - 55%, 73%, and 88% total THC. I wonder if they’re even still open.
I would also try to keep from excessive lab shopping - find one and stick with them until theres a really good reason to move on. And remember, there is no perfect lab and there will always be variation from lab to lab. Every time a measurement is taken error is being introduced. The observer affects the observed. Occasionally a mistake may happen. Talk to your lab and build a rapport. Robots aren’t doing all the work in labs yet, so a human still preps your samples and runs the instruments, and humans can be unreliable. Be kind.
It you have the resources, you can do some of the testing yourself. An old HPLC, like an Agilent 1100 or Waters 2695 can cost between 7-15K (lots of variation). Gas chromatography is also an option and keeps you away from messing with organic solvents like methanol, ACN, etc. Both do have ongoing consumable expenses.
If you have the cash, Agilent sells Diamond Attenuated Total Reflectance Fourier Transfer Infrared Spectroscopy instrument. You could do potency testing in under a minute, no solvents or adsorption material like c18 columns. You can use it to screen herbal material for CBD, THC etc. really; it can analyze any type of matrix (oil, flower etc). There is no sample prep with this method, very straightforward once it has been calibrated: