Test Results Over 100%

I have seen and gotten back test results with the total cannabinoids being over 100%. The % columns are the exact same as the mass column just with the decimal point moved over. This seems like a different sample size being used in each test. Some are over 1000mg/g and some are less. Can anyone explain this and how having something over 100% makes sense?

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It has to do with calibration, and variations in machine response. It’s fairly common, but also super annoying. When I do in house testing I have about a 1-2% per injection variability so when I see up to 101% I don’t mind. When I hit 102% I recalibrate and rested the samples, that usually works. If not then I have to trouble shoot more

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I recently had test results for disty that came back 98.8% THC, 4.8 % delta 8. No other cannabiniods.
I could either be really proud of my distillation or call bullshit. I’m leaning toward the latter.

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Even the best labs have a hard time being accurate 100% of the time. A little deviation is normal. We’ve gotten lab results for our isolate showing over 100% CBD, we just don’t use those because they look silly.

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I still liked our 105% results

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:newspaper_roll::exploding_head: @cyclopath

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Yea sometimes it seems really cool because when they use 1200mg/g it makes numbers higher than they really are so it would seem. Same thing when it is less though. Just have some come back that the sample mg/g was just over 800mg/g. The total THC only showed to be 68%. I feel it should be just a bit higher. -50 propane run of 50/50 keif and trim mix of fresh material.

This is interesting. I had a THCa pentane recryx sample I sent out to three different facilities out in Colorado. I had two come back above 107%, the latter being 114%. As I dont have any experience working with testing or analytics, I wasn’t sure if this was normal or not. I actually reached out to murphymurri as she used the same lab I got 114% from, and they told me to just sell it as 99%, and she claimed “Thats how testing works.”

I just have always been bothered by that. How is 114% an acceptable variance? I personally would rather know what my results more accurately are than to just market something incorrectly. But like I said, I have no experience in analytics and always wrote it off as a normal happenstance. Just has a sour feeling about it , though.

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Its hard to test near 100% because the normal variation in cannabis testing results is ±10%.
So if the real number is 95% then any result between 85.5% and 104.5% is a valid answer.
You would wish the answer could be less uncertain, but there are so many sources of error in the testing process that ±10% is actually good science. In environmental testing, like for air pollution, the variance is ±50%, so ±10% seems very precise by comparison. Its not sloppy procedures. Its just the limits of the current technology ( GC, HPLC or anything else ). If you spend $100,000 on equipment you don’t get any better precision than if you spend $10,000 on equipment.
Hugh Goldsmith
SRI

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So what is the deal with the mg/g variation? I have some that are as high as 1140mg/g and some that are as low as 800mg/g total cannabinoids. Is that actual mass of the sample being tested? From the results I am getting back this would make sense. And it would make sense to when you divide each cannabinoid by the total to get a % based on a 100% scale. But if this is not correct, is there a way to put these back on a 100 point scale so the % make sense?

If three different cannabis test labs have the same manufacturers 100k system and three companies have the same 10k system. Would they both stay consistent?

The comparison clears up a lot of doubt I had. Thank you for the explanation!

There are 1000milligrams ( mg ) in one gram ( 1 gram ). So 1000 milligrams per 1 gram is the same as saying 100%. 1% of a gram is 10milligrams so you could also say 10mg per gram ( 10mg/g ) is really the same thing as 1%. So, 1149mg/gram is the same thing as 114.9%. 800mg/gram is the same as saying 80%.
Its also helpful for me to remember that 1,000,000 parts per million (ppm ) is the same thing as 100%.
100,000 ppm is same as 10%.
10,000 ppm is the same as 1%
1000ppm is the same as .1%
100ppm is the same as .01%
10ppm is the same as .001%.
People talk in ppm when there are too many zeros in the number.
So it less complicated to say 10ppm instead of .001% because otherwise you get confused by the numbers of zeros.

But back to your real question about the variance between a result of 800 and 1140.
It seems like a big variation but if you take the average of 800 and 1140, that equals 970.
800 and 1140 are only 15% different from the average. 970/1140=.85.
So if you were a real lab and you got numbers which were 15% high and 15% low from the real number, you would only be a little worse that the typical lab which is ±10%.

Sometimes you can get less variable results if you do the testing yourself. It helps to run the sample 2-3 times and then take the average as long as the highest and lowest numbers are within 15% of each other. But commercial labs can’t run the sample over and over for the price they charge.

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Short answer is yes, the two labs should both be able to deliver ±10% accurate answers.
There is a built-in error between HPLC and GC test for flower samples because of the discrepancy when measuring the THCA/CBDA ( long story, but covered elsewhere in these posts ). But GC and HPLC deliver the same answer for decarboxylated oils. When the sample is decarboxylated GC and HPLC give the same answer. When the sample is fresh flower, the HPLC answer is always higher by 20-30%.
Its because the HPLC measures the THCA/CBDA and then multiplies the result by .877 rather than the real number ( .68 ) whereas the GC delivers the real number without mathmatical trickery.
Hugh Goldsmith
SRI

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The 1140 and 800 were two different strains and test. Sorry for any confusion. Shouldn’t these all be 1000mg/g sample sizes in theory? I get that there can be a variation between different test of the same sample and within a single sample as you guys have stated. So my question now is this. The 1140mg/g sample had around 892mg/g of THC after doing .877 conversion. They report this as 89.20% Total THC. But that 89.2% is of 1140mg/g. So they are pulling mg/g straight over to the % column and just moving the decimal point over. Not a true 100 point % scale. To get it back on a 100 point % scale you could divide 892 / 1140 = 78.24% Total THC. Or at least that is how normal %'s work. Does this make sense for these test? My results will go from 89 to 78 but that makes a little more sense it just being propane extract. And when I do this division across all my test, it rationally makes sense compared to what they actually report.

I can’t believe 1149mg/gram is the sample size. The sample size would just be miliigrams, not milligrams per gram. Most labs don’t report the sample size because it does not matter how much sample they use. When you process a sample you weigh some number of milligrams of the sample into a bottle.
Then you dissolve it in solvent like methanol or acetone.
Then you inject a tiny bit onto the GC or HPLC.
The answer then comes out in the units of mg/gram ( or percent ).
Its not really clear exactly how the lab arrived at the 89.2% answer. Typically they take the THCA result and multiply by .877 then add that to the d9THC ( decarbed THC ) result to come up with the 89.2% total.
Send the COA and maybe we can figure out what they did.

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Has happened a few times to me. Total cannabinoid content was at 113%. Couldn’t believe it. Got lab to recalibrate and haven’t had an issue since then.

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And that is why you should know the lab director personally…

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100%!!!