Building a Gas Chromatograph

Every separation so far has used a liquid to carry the sample. In 1952 Archer Martin and Anthony James — Martin again, eight years after paper chromatography — used a GAS instead, and the whole business got faster by a factor of a hundred. A gas is thin. Molecules diffuse through it quickly, so they find the stationary phase, partition into it and come back out again thousands of times a second rather than thousands of times an hour. That speed is why a gas chromatograph resolves a mixture in minutes where a column takes an afternoon, and it is why the method now sits in every forensic, environmental and flavour laboratory on earth. The catch is that the sample must survive being vaporised, so this works for what boils without decomposing: solvents, fuels, essential oils. You will build a working instrument from copper tube, an aquarium pump and a thermistor, and separate the components of a lavender oil you distilled yourself.