Guys, hi.
How to calculate a CO2 concentration (in ppm ) based on the values from the EGM-4 used as a chromatograph.
I have the next values recorded every second:
0 sec - 350 ppm
1 sec - 350 ppm
2 sec - 360 ppm
3 sec - 460 ppm
4 sec - 820 ppm
5 sec - 610 ppm
6 sec -410 ppm
7 sec - 380 ppm
8 sec - 351 ppm
9 sec - 350 ppm.
I have few ideas bu I can not decide what is a correct one.
The concentration of CO2 in your sample should be proportional to the area under the curve and/or to the maximum height of the CO2 peak above the baseline as it moves through the analyzer. You would need to run a series of standards of known concentration to determine a calibration curve that relates concentration to peak area (or peak height), then you would apply that relationship to your unknown samples.
In my experience, you will get the best precision with this kind of measurement when the gas flow through the analyzer is stable, when the same size sample is injected every time, and when the rate of sample injection is constant from one sample to the next.
An alternate (and simpler) approach is to turn off whatever pump is moving gas through the analyzer and then inject the gas directly into the analyzer. If you have enough sample to completely fill the entire measurement cell inside the analyzer, then the CO2 reading from the analyzer should be the same as the CO2 concentration of your sample. Again, you can test this by injecting gas standards of known concentration.
After writing all of this, I found that PP Systems has an application note that describes how to inject samples into the EGM-4. Perhaps it will be useful to you. https://ppsystems.com/wp-content/uploads/AN_EGM-4_Sample-Injection-Kit_20140307.pdf
Best of luck with your measurements.
Женя, you have to keep the stable and known gas-carrier flow rate (N2, CO2-free air, etc.) through your EGM. There are special electronic instruments to maintain the constant gas flow (200-400$). This is the most important condition to get reproducible results with the flow-injection method. Sure, you have to have the CO2 standard. These two items are really crucial and worth $$. The injector from PP recommended by Scott C. Neubauer is a good third option if you have a good budget. In fact, you can inject analyzed gas with a regular syringe and regular stopcock ...
Perfect! Спаcибо, Николай.
We have a nitrogen generator producing a current of the gas. And I have number of stopcocks and standarts.
I will use them for the next analysis.