For say we have collected methane gas sample using a fabricated chamber from water bodies and calculated the methane concentration in the gas sample using gas chromatography. Can we calculate the concentration of CO2 by following this method ?

Some studies says that CO2 is rapidally equillibrated with time so we have to measure CO2 on site by using IR sensors.

isn't it possible collecting CO2 samples over the time interval and then test them back in the laboratory.