Yeah I ran 3 separate 2nd dilutions of 6 different same batch samples. I was mostly controlling for pipetting, but taking observational data into account, it correlated. Now I’m thinking next thing to try is if I notice <10mL ACN, do I eyeball adding ACN to get to 10mL after the separation.
Has the device delivering the 10ml been interrogated?
Loss of solvent to matrix seems like it should take target with it, not concentrate target in remaining solvent.
Least that’s what I see with larger samples 
Evaporation sample during prep, or not adding enough in the first place both seem like they fit better.
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I would think that too, but I’ve consistently seen elevated results and not low results when analyzing the 2nd dilutions. I do think there is some evaporation but I will control for that and make sure the water/gummy solution is back to room temp before adding the ACN. Thanks! As far as the separation, the centrifuge is pretty consistent. I have not really controlled for that other than the RPMS and Time.
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Why are you using quetchers (spe) for potency? This is being ran on lc-uv right? Imo there is no reason to be using spe if not being ran on msms. Extract in meoh or meoh/acn, filter, then dilute (in same solvent as starting mobile phase).
Also if using air cushion pipettes, always prime the tip 3x with sample before delivering volume. This is very much needed when dispensing non-aquious solvents due to the difference in vapor pressure.
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I’m using the dSPE, not sure if that’s just a nomenclature difference, but I’ve found this method helpful with larger samples versus extracting a large gummy in only 10mL of mobile phase for lc-uv. I’ve developed a protocol now along side the quenchers protocol that is giving very comparable results to other ISO17025 labs after a few tweaks from the issues discussed above. Millipore Sigma has an SOP for HPLC analysis which was where I was working on this protocol from.
Overall, what I noticed is that the ACN was returning less than 10mL and the loss of mL in the aqueous layer did not contain analytes, but was just scantly miscible in the aqueous layer enough to concentrate the cannabinoids in the ACN separated.
Yeah the d just stands for dispersed, still a solid phase extraction just with powders bouncing around in your solution of interest. IME it is not really necessary for edibles potency on lc-uv. The dspe is not going to soak up too much lipids really and the small amount of sugars are not going to hurt the lc system much.
Have you tried just extracting in meoh/acn and dilution as compared to your dspe method? Do you see any interference with analytes in the regular extraction method? Are the concentrations off? I’d want a good reason to introduce dspe into a method considering all the extra prep time it takes. Less moving parts is better for business and accuracy of results.
Oh I see, you are using it for large edible units. Well I guess do what works for you. But you are probably losing some small amount of cannabinoids to the dspe particals and possibly the aqueous layer.
Possibly could scale up the extraction with just meoh (warm) in a 50ml tube? Not sure how big your gummies are.