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)