Chromatography Forum

Hi,
As part of a school project, I am constructing a simple gas chromatography device. The equipment will be set up as shown here: http://media.rsc.org/Classic%20Chem%20Demos/CCD-24.pdf. However, I have also found a design for, and built, a simple thermal conductivity detector (detailed here http://pubs.acs.org/doi/abs/10.1021/ed071p995 (behind paywall)). It utilises the variation in voltage dropped across a silicone diode with the thermal conductivity of the gas passing it to detect the presence of a substance. My question is; would the basic column built in the first link (washing powder as stationary phase) work with the thermal conductivity detector from the second link? If not, what sort of column would I need for the TCD? Also, if anyone knows this, why can washing powder be used as a stationary phase?

Sorry for all the unusual questions.

Thanks

That looks like fun !

The problem with using a thermal conductivity detector is that the thermal conductivity of the carrier gas (natural gas) is probably too close to that of hexane and pentane vapour. However, since you do not need to have a flame as in the original design you could use compressed air as carrier, although you would have to take precautions to prevent the hot detector from igniting the sample - air mixture. Can you get compressed nitrogen ? - lots of auto repair shops fill tyres with nitrogen, one tyre full would be more than enough to run the experiment but you will need a valve between the tyre and column to control the gas flow.

Please take video to show us how it goes.

Peter

Yeah, I should have access to some nitrogen at school. I'll look into it.
I don't think the detector will get hot enough to ignite the sample, it only uses a diode as both heater and detector.
I'll definitely try to take some videos of it in action.

There are lots of things that can be used as a stationary phase.

Surf is no exception. Look at the composition of Surf.

As long as it has an affinity for the analytes in question, and allows an equilibrium to be established between the carrier gas and itself for the analyte in question, it can be a stationary phase.

Oh, the old memories here in the US where the laundry detergent 'Tide' was once a stationary phase.

best wishes,

Rod