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Problems with calibration - 2005/11/28 18:29
facing problems for calibrating gases in a
6890 GC which has three gas sampling valves attached to it on top. I wanted to calibrate for hydrogen . I have a pressure gauge connected to the line close to GC. I know the line pressure i know the temperature, i know the flowrate ..i want to know the no. of mols. But the temp changes as soon as the gas enterd in the sample loop. I dont know the pressure there in the sample. So considering the line pressre , temp and flowrate if i calculate the no, of mols it would not represent the area in the chromatogram. Since everything is changed now. So should i go for sample loop volume, pressure , temp for calculating no. of ols or i would take the line pressure,temp,flowrate?
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admin
Admin
| Posts: 138 | |
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Problems with calibration - 2005/11/28 18:29
Usually, the sample loop is at atmospheric pressure before the injection is made. Therefore the amount of any gas injected will be a function of the temperature of the loop and the atmospheric pressure. You are right in saying that the pressure in the loop increases when you inject but that increase only serves to compress the sample gas, the mass sample does not change.
Out of interest what carrier gas are you using? If you are using a TCD, be careful, if your are using Helium as the carrier because the calibration for H2 is likely to be very non-linear.
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