Chances are good that most of us will live our lives without having to perform gas chromatography, and if we do have the opportunity to do so, it will likely be on a professional basis using a fairly expensive commercial instrument. This doesn’t mean you can’t Wind your gas chromatographHowever, if you make a few compromises, it won’t be that expensive.
Gas chromatography is essentially very simple; It is merely selectively retarding the movement of the gas phase using a solid matrix and measuring the physical or chemical properties of the discrete components of the gas as they pass through the system. That’s exactly what [Markus Bindhammer] It’s done here, in the simplest way possible. Gas chromatographs generally use a carrier gas such as helium to move the sample through the system. However, since these things are expensive, [Markus] I decided to use room air as a carrier.
The column itself is a meter or so of silicone tubing packed with tonal grade silica gel, which is probably the most expensive thing in the BOM. It also includes a homemade injection port made from brass compression fittings and some formed acrylic blocks. These devices contain detectors, an MQ-2 gas sensor, and a thermal conductivity sensor made from a wheat-shaped incandescent lamp filament. To read the sensors and control the air pump, [Markus] It uses an Arduino Uno, which unfortunately doesn’t have great resolution in its analog-to-digital converter. To fix this, use the ubiquitous HX7111 load cell amplifier to read the output from the thermal conductivity sensor.
After disinfecting the column and heating the sensors, [Markus] Inject a sample of lighter fuel and export the data to Excel. The MQ-2 clearly shows two parts coming out of the column, which makes sense for propane and butane mixtures in lighter fuels. You can also see two peaks in the thermal conductivity data from different fuels containing only butane, which correspond to the two different isomers of the four-carbon alkane.
[Markus] I’ve been on a bit of a tear lately. Just last week, we showed off his photochromic mnemonic device and, before that, his comprehensive electrochemistry laboratory.
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