Chromatography, what is it?

Science stupidfart9876 August 7, 2016 1 0
What is chromatography? It sounds very difficult but the principle is quite simple. I will explain what it is and what its uses are.

What is chromatography?

Chromatography is engaged in the distribution of materials. It touches on extraction and distillation, but it is not the same. Each material has different properties, and all these properties together distinguishes fabric A of substance B. Some substances, for example, dissolve well in alcohol and bad in water or vice versa. Or substance A has a boiling point of 80 degrees and substance B of 90 degrees. That kind of properties can be used to determine which substance is involved. A good way to explain this is on the basis of the known sample of pen and paper, and liquid which is also known thin-layer chromatography is referred to.


How does it work? You need paper, pens and an eluent. An eluent is often simply a liquid mixture of water-alcohol, and ammonia. The first thing you do is with pencil draw a line at 2 cm from the bottom. In this line are the points put down markers. The paper is then suspended in the eluent. The paper takes the eluent and slowly flow upward. And as it flows it takes up the dyes also note that dissolve well in the eluent. If a dye dissolves then goes to this very far up. If it does not dissolve or poorly dissolves remains hanging down or a little bit. When the paper has passed through 80% of the paper is taken out and it is with a pencil the endpoint of the liquid passed to. The area between the two pencil lines is called the solvent front. When one puts a dot in the center of the spots, one can calculate a Rf value. Rf starting center spot / start solvent front. Each dye has its own Rf value, the R f value is constant under the same conditions. When you compose a different eluent can change the Rf value because the dye then dissolves better or worse. When one suspects for the case of dyes which can also be adjacent to the stylus point to make the pure dyes to see if this is indeed those colors. In this way, it can be determined which dyes there are in a stylus.


A frequently used chromatographic method is liquid chromatography. HPLC stands for High Performance Liquid Chromatography. HPLC is an expensive piece of equipment and the necessary fluids are very expensive, there hand, the method can quickly and precisely done. That is why you see them mainly in large laboratories. HPLC is composed of an eluent, pump system, injector, column, detector and a computer. The eluent often consists of methanol and water. With the pump system in the mobile phase can be composed. If one is in the injection syringe, the eluent the required fluid will be pumped to the injection system and from there to the column. In the column it is made difficult for the molecules to penetrate by generating high pressure is required. The small well-soluble molecules will be the first to leave the column, and in which are taken by the detector, the large molecules, and poorly soluble molecules as the last. If the detector detects a material which transmits the information to the computer. The computer then shows a graph with time on the horizontal axis. The time at which a substance is to leave the column under the same conditions always exactly the same, and is referred to as the retention time. If one knows the retention time of the desired substance in these circumstances knows one sees equal or dust inside it. But they do not yet know in what concentration. Therefore, the peak area should be calculated and a calibration curve are made.

Gas chromatography

A gas chromatograph is basically the same as the HPLC measurement only works and these gases in place of liquids. A carrier gas is used here in place of eluant which increases the pressure in the column. Indeed, there is not needed as the eluent in a gaseous state all the substances are dissolved 100%.

Disadvantages of HPLC and GC

It is quite expensive. both the equipment and the liquids. The liquids must be namely HPLC grade, which is extremely pure. In self distil water is not pure enough. For the methanol helium is also used to create the gas-free. Helium is also pricey.

Advantages of HPLC and GC

The provisions are quick to implement and there are many analyzes can be done consecutively. This makes the method little labor-intensive which is an advantage. The method is very accurate. And the smallest quantities can be detected and determined.