We are an industrial hemp processor. We are using an HPLC (UV not PDA). The results we are receiving after each thirteen-minute run are consistently skewed and do not match within certain degrees of freedom with third party potency results. The CBD results are off their mark by nearly 30-40%. These results vary from sample to sample, and samples tested in tandem from the same vial will give differing results of up to 5%. Our lab has changed the sample prep multiple times including: time study of the samples sitting in the methanol used to extract the cannabinoids to see if more time would be beneficial, using a vortex to mix the sample, adding an eight-minute run in the 62° C sonication hot-bath, and changing filter types. None of the amendments to the sample prep have added any noticeable positive results to the data received from the HPLC. The total cannabinoid potency tests cannot be assumed as accurate at this time. We want to be testing Flower, Crude, and Distillate. We are looking to hire a consultant to fix this ASAP.
What method are you running?
What grade solvents are you using?
Have you verified the flowrate through the column?
Are you using a column oven?
What pipettes are you using for sample dilution? Are you properly using said pipettes, holding them vertically and fully discharging all the liquid from the tips?
Are the pipettes calibrated? How often do you test that calibration?
What kind of scale are you using? Can it read to at least 0.01mg? When was it last calibrated?
What liquid handling instruments did you use while diluting standards for calibration? Are they calibrated?
Are you centrifuging the sample before you filter?
Also, what brand column are you using? What are the dimensions? How many injections have been made on the column? Was it bought new or used?
I once ran a potency testing lab and I’d be happy to consult over this. I have established methods that have passed accreditation.
Are you calibrating your HPLC machine with reference standards?
How are you injecting? Manual or autosampler? Have you checked your pippetting technique by pippetting and also checking microliter syringe by dropping water on an analytical balance? 1 microliter = 1 milligram.
Also how do you calibrate your analytical balance?