I'm currently working on a batch type gas phase photocatalytic reaction. For product analysis, i draw the gas samples from the reactor using a gas tight syringe and then inject directly into the GC column (GC TCD/FID) through septum. As for now, I'm using 0.5ml of gas samples, but i found that there is poor data reproducibility and the signal for CO peak is too strong for both TCD and FID throughout reaction period. I'm aware that FID should not detect CO but in my case the signal for CO is HUGE! However, I'm getting good results for other gas products such as H2, C2H6 and C2H4. I suspect the volume of gas sample could be one of the reasons, therefore if anyone have experience in analyzing gas samples by manually injecting into GC, please share your thoughts. Thanks in advance.
There is poor data reproducibility because you are using a very small sample. However, 0.5 ml gas sample is enough for analysis, provided you have an online GC system and there is a continuous gas flow to GC.
But for the batch samples, you may use gas bags containing at least 50 ml gas sample, because when you take batch sample there may be some atmospheric gases in the surrounding which may enter GC input line, due to which the reading becomes absurd.
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