I expect my samples to have formic acid, methanol and formaldehyde. However, I have problems analyzing the samples using GC-FID in term of the GC methodology. Can anyone who has experience with this situation share their methods with me?
What kind of problems do you have? The peaks don't appear or are they overlapping? I think that you can also try mass spectrometery where you can get the masses for your expected product. I hope/wish that it might work for you!
Good luck!
The response of the FID for formaldehyde and formic acid is very poor (due to C=O). Hence, you need to develop an alternative strategy to detect these compounds, viz.
1. change the detector to TCD or MS
2. Put a methanator before the FID
I think that Eric Steen gave the perfect answers for this problem.
thank you for the information..my sample is in liquid form and containing water..however, the technician incharge in GC MS and GC FID informed that the equipment could not test sample containing water..So, how can I test my sample?
It all depends on the column you use. Make sure you use water tolerant columns like aqua wax. Also inject no more than 1uL to avoid back flush. As indicated by Eric you'll have a hard time trying to analyze formaldehyde and formic acid using FID. Another way can be H-NMR which can go to low concentrations as well.
Instead of FID use TCD detector and your detectability of HCOOH and CH2O could be solved. As a filling of chromatographic column use Chromosorb 102 /80 to 120 mesh/, length 120 cm and diameter 3.5 mm. This polymer is satisfactorily water resistant. Dont exceed the injected volume of 1 to 1.5 microliter.
You may run analysis isothermally at temperatures 100 to 160 oC. Optimize the resolution by changing the thermostat temperature in this interval, keep injector and detector temperatures over 110 oC, and use a direct sample injection into the column. You can also improve the resolution by moderate changing the flowrate of carier gas.
To achieve better resolution and higher signals you could use He as a carier gas. In case that concentration of analyts is very low, use H2 as a carrier gass. In this case pay attention, H2 in a mixture with air is explosive.
The response of TCD will be higher due to hydrogen lower thermal capacity, compared with He.
R.S.
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