Can anyone help me understand this Chromatogram ?

This is cannabis tested in Thailand i was wondering if it is possible to figure out the percentage of each component.

In info or feedback would be appreciated

no, I don’t believe anyone can take that and give you concentrations of the various components.

what you’ve got up is the results from two different UV wavelengths on what looks to be a old (evidence of decarbed + CBN) “high cbd” flower.

the best anyone will be able to do is give you a guess on ratios. as you can see looking at the THC/THCA pair, the apparent ratio changes based on the wave length. because they absorb differently at those wavelengths.

you’ve shown only part of the report. I’m guessing there is at least one more wavelength, then presumably the numbers you’re after. can we see the rest of it?

@drjackhughes? @doc_simple? @drPaul?

Unfortunately this is the only page that I have from the report. This was actually made from Thai or Loas compressed cannabis.
I am planning on sending some of this cannabis and some of the oil that we are making from this cannabis to the states to be tested in a lab.
Thanks a lot for the feedback.
Is there anything else that you might be able to tell from looking at this graph?

Here’s an old chemistry trick before integration was automated. Cut out the peaks and weigh them on a precise scale. For the known cannabinoids use the data at 228 to do this. So you can weigh all the stuff that isn’t cannabinoids together, weigh the cannabinoid peaks and take a weighted average. Mass of peak/total mass of all peaks (I think I got that right, I’ve never done this but heard tell of it in grad school).

Check out this paper and you will see that the typical cannabinoid UV-vis spectra absorb less at 270 as compared to 228. 2005-Spectroscopicdataofcannabinoids Hazekamp et al, 2005.pdf (748.3 KB)


That is brilliant!!


Compressed huh?

I was going to suggest that the cbd:thc looked a little like imported hash samples collected in the UK. That data is around here somewhere (It’s in the data dump). Probably a PhD thesis if I’m recalling correctly. Couldn’t tell you from memory. Not going to try and find it on my phone…

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Boy, it’s been a LONG time since I’ve heard anyone talk about cutting up and weighing peaks! Really long!!

That will certainly work, and the advice on which wavelength to use also sounds right. To make it easier you could measure peak heights, and multiply by the width at ‘half-height’ to approximate area, and do the accumulation of total areas to roughly estimate total cannabinoids, percentages, etc. That’s what I did in '79 to quantify trimethylsilyl sugar derivatives from alfalfa (!).


Thanks a lot for the feedback guys. I think the cutting up and weighing the Peaks is a little beyond my expertise. But thanks a lot I will see if I can find any more information on this graph and post it here.

because you don’t have a suitable balance?

you literally print that picture, and cut out the triangles, then weight the paper to determine the relative areas… the ratio of CBA+CBD triangle to THCA + THC triangle gives CBD:THC…etc

Edit: suddenly the relationship between grade school and grad school becomes shockingly apparent…one gives you sharper scissors. :man_facepalming:


Okay, now I completely understand. Thank you for that

OMG when I saw the “cut out the paper” i almost peed myself. That is some old school tech right there :joy::joy:

doesn’t make it wrong though!

So I’m not sure about this, does hplc elute compounds similar to GC? It’s been a while since I compared the two but retention times are retention times. I guess the solvent used in the hplc could shift things based on affinity…



Yep, it’s still about retention time.

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My take on retention order (GC vs: HPLC) is that in general, GC retention is largely dependent on boiling point, while HPLC (reversed phase, anyway) is more dependent on hydrophobic interactions with the organic part of the stationary phase (the C8, C18 ‘coating’ of the solid phase particles). With GC you ramp up in temperature to give high-boilers a chance to move, and in HPLC you ramp up in mobile phase organic content to overcome affinity with the stationary phase.