HELP

Discussions about GC and other "gas phase" separation techniques.

4 posts Page 1 of 1
Hello everyone,

I am experiencing reduced peak area/height of butanol on my Nexis GC. The problem aroused suddenly, and I can't figure out why. It is causing issues in manner that I can't analyze 5% of butanol anymore (peak is not showing on chromatogram). I am analyzing mixtures of organic solvents from v/v 0,05 % up to v/v 100%. All other peaks are showing good result. Some suggestions why area/height of specific analyte would suddenly reduce.

Thank you for reading.
Nobody can help you unless you tell us what method you are using and what the conditions are.
Peter Apps
Thank you for reading.

I am working on a gas chromatograph with a FID detector to analyze organic solvents like butanol. The stationary phase is SH-I-624Sil MS 60 m, 0,25 mmID, 1,40 μm df. 1 uL of sample is injected into the chromatograph. The analysis is carried out at a nitrogen flow through the column of 2.5 mL/min at a split ratio of 240. The temperature of the injector is 220 °C, and the temperature of the FID detector is 250 °C. The flow of compensating gas (N2) is 25.0 mL/min, hydrogen 32.0 mL/min and air 200.0 mL/min in the detector.

So far, there have been no problems with any analyte except butanol. I changed split ratio from 240 to 100 or less but nothing.
If only the butanol is affected (and there are no other alcohols in the solvents you analyse) then it is most likely being adsorbed by dirt in the inlet liner or active sotes on the column.

Try chaging the liner first. If that dopes not work, cut the fiorst 50 cm off the column.

2.4 ml of nitrogen into a 0,25 mm id column is way above the optimum flow - why do you have it set like that?

Peter
Peter Apps
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