Chromatography Forum

Hi!

Well this is my first question to the community! i am Pramit, working with Gas Chromatography for developing a hydrogen sensor. This is what I do:

I have a normal gas injection procedure with a rotational valve.

The sample loop volume is 1 mL and 1 metere length, enclosed in a chamber at 60 deg C controlled temperature.

One end of sample loop connected to an MFC to flush the sample loop with measurable gas mixture before injecting. And other end open to ambient.

To calculate the concentrations from area, I calculate the molar volume of the gas at given temperature and PRESSURE. If I measure at 50 mL/min, an overpressure of 15 mBar at inlet of sample loop and outlet remains at ambient, what pressure can use to calculate my molar volume?

I sincerely thank you for the time and would deeply appreciate some replies on this fundamental question.

Regards
Pramit

If you stop the flow at the inlet end of the loop a second before closing the outlet, then the pressure in the loop should have equalized to ambient atmospheric pressure. The pressure at the inlet is measuring the flow versus the restriction to flow, but once the flow stops the gas in the loop should quickly equalize with the outside pressure at the end of the loop, so just look at the barometric pressure and that should be the pressure in the loop, if you have no restriction at the end.