A drop of water falls on the paper where you have just written something, the black ink is poured and turns out to be composed of different colors, three or four, or maybe a small iris.
seems a trivial thing, but instead is the starting point of chromatography, one of the most beautiful and complete chemical analysis. The beginning, historically, are with his "paper chromatography" means a paper towel is soaked in water for a corner, and waits patiently for the water goes back up the whole sheet of paper. In back, the water drag several parts that make up the mixture that we are looking at: If you have colored, it is easy to see and recognize them.
Subsequently, the method of analysis has been completed, but always without a fixed phase (the card, or a resin in a column) and a mobile phase, which may be water, alcohol or any solvent as long as fit for purpose . For example, a glass tube with a tap at the bottom, filled with suitable material to hold in a different way the test sample, and a liquid that is poured from above. From the tap at the bottom, samples are taken at specific time intervals, which are then analyzed separately.
And finally, the gas chromatography: the sample is vaporized into a small oven, and flows into a long coiled column and filled with specially selected material, driven not by a liquid but a gas. The hydrogen gas can be (very good but dangerous) or helium (the one to fly the balloons), or even nitrogen, which is inexpensive and completely inert. Can be analyzed with gas chromatography oils and fats, and you can even go and see with that is that a semi seed oil, and if olive oil is really made with olives. To an expert analyst, this is not a very arduous task.
At work, where we used gas chromatographs often, sometimes things happen like this: One morning
Joseph comes to us, a worker from Puglia. Joseph was made to send a carboy of olive oil from his country. Puglia is famous for its olive oil, but Joseph does not trust the driver that led to the carboy, and seeking help from us in the laboratory does not fall in our duties, but today there is time, we must test the new column, and is a good diversion from the routine.
So let us go to see a bit 'of sacred texts: the olive oil should be given, in gas chromatography, a single peak: the peak of oleic acid, which comes out very late on our instrument, after more than twenty minutes. If the path of gas chromatography, a peak first twenty minutes, this is undoubtedly a lighter fat oleic acid, a soybean oil, corn or even rape ...
At the end of the analysis, there he is, relentless, the peak of sunflower oil and the verdict:
- Unfortunately, you were right, Joseph, your olive oil has been cut with vegetable oil: a beautiful 5 %.
- Five liters, if they have cheated, that unfortunate ... but now I feel when I see him I say four, points out that if a piece!
(Giuliano, June 2004)
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