Issues With Water Soluble Testing

I’m having a recurring testing issue with the water soluble we’re producing in house. We’re emulsifying distillate (~80% CBD content) into an acacia gum/water mixture and we’re getting really inconsistent results…it’s usually between 10-30% low even though I’m dosing the product 10% higher.

I’ve sent it to both Gobi and Botanacor in CO and gotten a decent amount of variation even testing the same sample. I’m hoping someone has some insight because I’m starting to feel crazy.


Yep. This has come up before. Can’t find it in the 60sec I dedicated to the task.

You’ll need to work closely with your 3rd party lab to solve this.


Got it, it sounds like it’s probably a sample preparation issue. A technical support person I spoke to at a different lab said different prep methods exist that work for some emulsions but not others.

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solving it will require working with the director or head chemist. possibly several different labs till you find one willing to solve it.

first they have to admit that their numbers are off…which can take some finesse to get across without making them defensive. then they need to investigate the problem. they’ll want money for that. being clear that you’re willing to pay (negotiating how much) upfront can be helpful getting them on board.

maybe @kcalabs can explain how they’d approach it if you were their customer.

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How much work have you spent ensuring your formulation itself isn’t a problem or a major contribution to the inconsistent results?

While there is certainly a lot of possibility that the testing lab could be off, there is also the possibility that the product itself isn’t as homogenous or emulsified as thought to be. Depending on how and when the sample is taken, that could certainly contribute to some variability in the final result.

That isn’t saying the testing labs might need to improve their sample preparation for this matrix, but there very well could be some potential for the product itself to not be as homogenous or stable as thought, thus some of that variability could naturally be introduced from the product itself and is out of control of the lab.

If you have already confirmed that the same sample, being prepared by the same lab, using the same technique, is exhibiting variability outside of expected variability for the methodology then I would lend that problem to more than just the sample preparation itself. Often times, and this is only speaking anecdotally from my experience doing analytical sample preparation and quantification, unless you need to perform some kind of special derivatization reaction or you’re working with some very unique matrix, I would expect the results to be somewhat comparable to each other even if they are off the mark from what they are formulated to be. In other words, while the sample preparation may need to be refined or altered to ensure the results are both accurate and precise, having such large variability within a single set of common data points (same sample, same lab, same method, same sample prep) would lead me to believe the formulation itself may have some inherent issues with its homogeneity and stability.

As cyclopath has said, this is something you will most likely need to work closely with the analytical team to verify and it will most likely require a combination of verifying as best to your ability the stability and homogeneity of your product as well as if there are any parts of the sample preparation that could be improved for this specific matrix.


Agreed 100%

“Always low, and consistently so” is a sample prep/matrix issue, “low, and all over the map” is more likely a formulation issue.

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Happy to test it first, maybe we’ll be spot on?

Yes, it sounds like a prep issue/solution.

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I really appreciate how in depth your response is and I agree that the homogeneity/stability of the water soluble could be the culprit here.

I’m trying to figure out how to assess it definitively because after compiling historical data over the past year it’s more “all over the map” than consistently low. If stability was an issue I would expect the CBD content to decrease over time as it crashes out of solution (which I don’t have data for). I could send 3 samples pulled from the same batch at the same time and have a lab test it. I’d assume 3 samples pulled at the same time from the same batch would test similarly even if the emulsion was unstable but I’m not sure.

Any thoughts here?

assuming homogeneity, yes. probably. if it was super unstable it might lose homogeneity after sampling.

This is very helpful. Having compiled a lot more historical data it seems more likely it’s a formulation issue. I’m just not sure how to diagnose it.

Do you think testing the same batch weekly and looking for a decrease in CBD content is a reasonable way to test that hypothesis? Or is there a lab method for testing emulsions?

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Ok, I’ll have three samples tested from this most recent batch. Thank you @cyclopath!

I can speak to this from the other angle, as I was QA Manager of a lab that was accused of giving inconsistent results on water soluble back in the day. It turned out after extended analysis that we were completely right and it was the manufacturer who was wrong.

Generally speaking the first step in sample prep is to take an aliquot of the emulsion and dilute it in a comparatively very large volume of ethanol/methanol/acetonitrile. This has the effect of basically breaking down the emulsion instantly (as the water concentration has become trace, no longer facilitating micelles). This is then analyzed by the standard route to give a mass balance.

If your emulsion isn’t great you could potentially see settling of the high cannabinoids layer and if they’re not re-homogenizing the sample before pulling the aliquot there could be like stratification or something (they should at least be vortexing it, but on the other hand, if there’s something like that going on your product really needs to be made more stable)… but once it’s put into the working solvent I don’t see what they could be doing wrong from that point on.


Thanks for the reply. Troubleshooting an issue where you’re reliant on someone else’s work definitely adds another layer of complexity and blaming the other guy is always easier. But this process is being made a lot easier by people like you giving insight into the process because at the moment it’s a black box (I’m trying to get my testing partner in on this but haven’t heard back yet).

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I would potentially start with doing a particle size distribution and analysis. If you have a proper nanoemulsion you should not only have an average particle size less than 200nm but you should also have a very clean distribution curve, it should almost look like a peak from a chromatogram.

I don’t know what your system is made of but if you are using any kind of ionic surfactants you can also determine your formulations zeta potential, which CAN but not always, give some insight into the potential stability.

If you let the solution sit for a day or two when mixed into water or something else, do you see any separation over time? Or even the base emulsion, do you notice any signs that you could have some separation of your cannabinoids through forming large micelles or other things like that? Those would be my initial suggestions to at least rule out there could be some issues on your end. And again, I am not saying you’re at fault, or the lab, but it always helps to be sure you’re confident with your formulation when approaching the lab. I would also approach the lab with this data and show them what you have done to try to verify stability and homogeneity of your formulation. Doing this will help the lab potentially understand your product as well as make the discussions about their methods potentially being problematic seem less finger pointing and aggressive and that you are coming to them to work as a partner instead of blaming them for inaccurate and imprecise results.

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Very important piece of the puzzle & sound advice!!

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Can personally attest that every water soluble product that I have had tested at KCA has come back within 4% of target formulation. I’m sure the briefcases of cash helped that along. Just playing, KCA has been spot on with most of the stuff we have sent their way!

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Love to hear it @MedicineManHempCo @kcalabs. I’m going to do the characterization work outlined above and assuming that all checks out you’ll be hearing from me!

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Is an average particle size of less than 200 nm an indication of stability? At that range there shouldn’t be a lot of CBD crashing out?

I wouldn’t say it is a sole indicator but there are plenty of studies out there that support the smaller your particle size is for an emulsion, the more stability that emulsion will have. Particle size distribution is also just as important. If you have a wide range of particle sizes that might tell me your emulsion is seeing some level of phase separation and you have formation of varying sized hydrophobic micelles in the emulsion.

I wouldn’t say 200nm is a hard number to say everything above or below is unstable or stable, but particle size definitely plays a significant role in the entire system, especially if you are trying to develop or produce a water soluble nanoemulsion (I am assuming nanoemulsion as that’s often times the target for these types of products).

This is why these types of analysis on formulations are important to do at the start of formulation development. For example, I would submit 5-10 prototypes at a time to the lab for particle size analysis before I would attempt to move the formulation to other stability tests or further down the product development pipeline. When I had landed on a formulation that showed all the signs of stability that I needed it to show, I finally started to do more quantitative analysis and I never had any issues with homogeneity testing or potency testing by the time I got to that point.

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Got it. I’ve been doing a lot of research in the past few days and it’s all implying we have stability issues. I’m going to rule out the lab testing variable and then focus on product stability. I inherited this process and I doubt any of this work was done.

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