-
- Posts: 12
- Joined: Fri Nov 04, 2022 9:21 pm
- Location: Canada
I am trying to calibrate a SRI310C Gas Chromatograph with a Restek MXT-502.2 column for residual solvent analysis.
The analysis is for residual heptane or methanol on cannabinoid isolates.
My current procedure for calibration is:
In headspace vials,
1uL Hept. in 0.1351g sodium bicarbonate = 5000ppm
1uL Hept. in 0.1692g "" = 4000ppm
etc. until
0.2uL Hept. in 0.2717g "" = 500ppm
with a blank thats just filled with 0.3039g bicarb.
GC Program:
Heated Injector 260C
Start 45C ramp up to 200C
25uL injection
The issue I am having is that the peak area for 5000ppm ranges from 15,060 to 17,520, and the peak area for 4000ppm ranges from 16,660 to 17,190 and so on, it holds pretty constant.
The blank doesn't have any peak which is good.
The peak area should be decreasing as the ppm decreases though.
Am I right in thinking that because cannabinoids are soluble in heptane/methanol, but the sodium bicarb I am using in place of isolate is not soluble in heptane/methanol this is messing up my calibration?
If not, then what should I be trying?