Thumbs up emoji… that is good homework for HS Chem I’d guess
Like to point out those are examples of things that would totally dissolve in the extraction solvent and would be expected to be homogeneous throughout the liquid solution. So there are definitely instances where it is appropriate to add sample vol to extraction vol… Like sugar going into water… Or like dabs going into meoh.
But flower don’t dissolve in meoh (not even half of it), so that extraction logic is not appropriate for flower.
Would someone like to actually refute that point? Or we just going to suck off the aoac guys all day?
If you used volumetric glassware… you’d be going volume to volume or volume to weight. Not w/w - and you’d be filling to the precise amount of volume, where you start with ~half the volume, add the weight, and then finish filling to volume. This gives you a specific molarity based on weight and volume. I’m sure you know this - some of your comments just seem to imply that you don’t.
I’m expecting it to be a variance of +/-10% or so - 10% of the result, not 10 points. So I’d expect say, 20% +/- 2%, not 10 - 30%. What I’m seeing just now is +/- more than 5 points in some cases. Its just dreadful. And talking to the labs about it has been hard going. I’ve got a legal label claim to meet at +/- 10% of the true value - and they can’t consistently confirm their measurement uncertainty is less than that! Sad days.
Perhaps - Chloroform or dichloromethane or pentane or separating out different kinds of hexanes. There’s work for all of these out there - so having it all in one place would be nice. Sometimes I consider putting together a white paper about it. Seems to me having all the solubility information would be helpful for our work.
Amazingly enough - even if flower doesn’t dissolve - you still know the total amount of solvent and can then calculate the total amount from the instrument back into the amount that was present in the flower. The steps are very clear for filtering off the flower (leaving behind everything soluble in EtOH).
And hell its basically the same steps you say to use, except you don’t appear to be using volumetric glassware - you’re just taking a swag at it. Which is probably why people not using these methods have more variability than people using these methods. Reducing your measurement uncertainty is important - and this is one method to do so.
Not sure why you seem to be against compendial methods. Acting like experts in our fields are somehow incapable of doing good science… I just don’t understand. We’re talking about hundreds of cannabis testing facilities all over the US and the world - working together to say that this method works.
And anyone can participate in this work. Anyone can comment. You could comment. It might even be helpful for the greater good if you did so. Because like the compendial methods or not - these will become the regulated testing standards that everyone will have to use in legal markets. Indeed these are already the methods required by the USDA for all Hemp products. And they are already becoming the required methods in states around the country for MMJ and REC markets.
And these are already the methods being used by the crime testing labs (because they use compendial methods) - so either your method has the same level of precision and accuracy of these methods or better - or you’re giving people test results that might send them to jail. And that’s not good.
The total amount of starting solvent is 50mL to volume. So that would be 50mL minus the very small amount that will be replaced by the cannabinoids that are extracted from the flower during the extraction process. And then you can dilute from there. So you always have a known amount of volume (50mL, aliquot into 100uL into 900uL, aliquot into 100uL into 900uL, etc).
I like @SidViscous statement about going gravimetric (instead of volumetric) - but I’ve never been able to afford these much fancier weighing/dispensing systems. Is that what everyone is doing now?
Or is everyone using solvent dispensing mechanisms like what @Labdog says he is using?
I know there’s still people out using pipettes. Is that the kind of dispensing you are talking about?
I always thought it was impossible to use gravimetric stuff - unless you already knew the density of the material you were weighing out (which we often don’t know…but I suppose we could calculate before we weighed it out to create this sample…)
So in your scenario you put 5g of sample in a container and bring to 50ml with about 45ml of solvent? Then without the sample dissolving the analytes are now assumed to be homogeneous throughout 50ml of solvent? Gravametric or volumetric, that is dumb logic. Is this aoac logic too?
And if you want to effectively/easily dispense a known volume of solvent within a known accuracy range, they make these things called positive displacement pipettes… And if you really want to get the weight… 6x reps of the dispense on the balance and average? Logic is a crazy tool yall
One that has legal rec and is not requiring any particular method just proof of validation and PTs and Iso/tni quality system. But none of that will ensure accurate results… Only sound logic and robust method design… Oh and motivation by the lab to not inflate results.
You guys know what motivates mj growers? Not accurate results really but they still get them from our lab.
Are you trying to “get me” and prove me personally/professionally wrong by looking at my states testing regs? Sorry but I reviewed our states regs two months ago… Still all good despite some recent changes to sampling requirements.
You want to refute my central point that methods already in use are better/more robust/economcal than aoac methods? Go ahead I am listening. Adhominem attacks and whatabboutisms will not impress.
Answer me this, Does the weight of the flower get added to the extraction solvent volume (or weight) containing the extracted analytes? Are the analytes in the solid sample at the same concentration as in the liquid extraction solvent? How would one figure out the amount of analytes that remained in the solid sample after extraction?
Well the general tone of the forum does make me a bit paranoid but I am still here for some good faith discussions. I don’t assume all members are acting in bad faith, but you specifically asking me for info not related to my point is pointing to bad faith.
Am I missing your point? Do you just want to talk about my favorite local ball team? Or what is your point in asking my state?
Honestly, I am concerned about sending my company’s licensed cannabis products to your testing lab. If you are not in my state, then I do not need to be concerned about this.
That’s not bad faith. It is just me doing my job (i.e., looking out for the best interests of my company).
Agreed, I will gladly not test your stuff. Next time you meet a lab supervisor ask them if they follow aoac methods or just plain lay out the method you want them to use. We will note it is each other and go our separate ways. Agreed?
So you are agreeing with me on 5g sample + 50g solvent is a 1/10 dilution if the sample stays solid. We just disagree on a second pass being necessary.
I have done a recovery study on my methods, and the second pass is unnecessary. Less than 1% of analytes left in the solids.
