Good Afternoon Everyone,
We just received a new Shimadzu HPLC this last week and are getting everything set up for our in house potency tests.
We run a THC remediation laboratory and have been using 3rd party laboratories to determine when our Distillate is “T-free” or below the limit of detection.
However, now that I am using my own HPLC I need to figure out what exactly “non-detectable” means in terms of HPLC values.
I have heard that LOD is around 100PPB for THC however what I am trying to figure out is what the average sample injection size is?
For example, if I were to measure 100mg of Distillate with 400x dilution I would be injecting 0.25mg/ml or 250ug/ml. If my LOD was 100PPB or 0.1ug/ml then that will give me a value of 0.04% dry weight as the LOD.
However, if I were to instead measure 400mg of Disitllate with 400x dilution I would end up injecting 1000ug/ml which would drop my LOD to 0.01% Dry weight.
Is there some kind of accepted standard in the industry for what “non-detectable” is considered?
Thank you all in advance, and sorry for the long question.
LOD depends on your own procedure and instrument. It is defined as a peak 3x the size of the baseline’s random fluctuations.
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Thank you for the reply! This is very useful info.
I suppose the problem is that I do not know how 3rd party labs are prepping their samples and while one sample prepped at a 400x Dilution may come back with a THC peak smaller than 3x the size of the baseline’s random fluctuations but a 100x Dilution will then have it within detectable limits.
Do you have any idea what the typical injection concentration would be?
I aim to be in the center of the calibration curve which I am currently operating with 0.5ug/ml-125ug/ml.
However, my concern is for a 3rd party lab who has a calibration curve up to 1mg/ml because the center of their calibration curve is approximately 10x higher than mine.
Any thoughts on that?
The lab will tell you what the equivalent potency to LOD is on their method. That’s all you really need to know. They will for instance say “our LOD is 0.1% for concentrates”. You, when doing your own method development, should aim to have a method where your LOD is below theirs. Whether you accomplish this with a 100X dilution or a 400X dilution is up to you. But if you determine your potency is below their LOD, for a particular sample type, you should be fine.
A Shimadzu HPLC should be able to detect concentrates even on very small dilutions – up to 4000X and still get good signal.
If you want help on this I am happy to consult. I am very familiar with HPLC testing and I have used Shimadzu units most frequently.
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Thank you very much, that was a very helpful comment. I will definitely keep you in mind if I run into more issues!
IMO non-detectable is truly in the eyes of the beholder. if you’re willing to look hard enough, there is always going to be detectable THC in there.
from an economic stand point, third party labs don’t want to look any harder than the law says they need to. ok, just a little bit harder than the legislated “failure” limit, but not a whole lot more, because it sucks to tell the customer than it passed state testing, but you can still see what ever it was you were testing for and hoping not to find.
in practice I think you’ll find that at less than 10x (usually closer to 3x) lower than than the legal limit, most labs will tell you they “can’t see it”, when in fact their instrumentation could go three or 5 orders of magnitude lower if they were paid to do so.
or perhaps @MagisterChemist could correct me?
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Yes that does appear to be the case I’ve been finding. Some labs I’ve spoken with consider <0.1% to be “non-detectable” others have told me they go down to <0.02% by dry weight.
I suppose I would want to be cautious and aim for the lowest possible levels but it’s frustrating to know that if I was just using a different lab my results would be “Non-detectable”
Yeah it’s procedure dependent. If i run a sample at 4000x dilution and it’s below LOD, if i wanted to i could run it again at 400x and now i would be able to see it. It can only be defined when you’re running the exact same procedure every time.
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Do you have any opinions on a Dry weight% to shoot for?
I don’t even know what you mean by that. But for flower around 10% is typical
Sorry for the non-specific question.
I mean Dry weight percent that is considered LOD for concentrates.
For example 0.1% THC by weight or 0.01% THC by weight.
I can’t answer that question for you. That is just a matter of your own desires. I would shoot for something lower than whatever the typical labs you’re using for compliance are doing.
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