Chromatography is a laboratory technique for the separation of a mixture. A Chromatography column is a device used in chromatography for the separation of chemical compounds. Five methods will use columns: GC, LC, IEC, SEC and chiral chromatography. Today, we share two methods between them-Gas the chromatography column and the HPLC column.
Gas chromatography column
In gas chromatography, the mobile phase is gas. The length of the gas chromatography column between 1M and 100M. GC: The liquid phase stationary phase is bound or adsorbed on the surface of the capillary column, or bound to the solid carrier packed in the column. The polarities of the matched analyte and the stationary phase have similar polarity. The thickness of the stationary phase is between 0.1 and 8 µm, and the thicker the thickness, the more volatile the analyte.
HPLC chromatography
HPLC is one of the liquid chromatography. There are three basic kinds of liquid column: Liquid-Liquid, Liquid-Solid and Ion exchange. Liquid-liquid chromatographic columns are less popular because of their limited stability and inconveniences. The stationary phase is solid in the Liquid-solid chromatography column. The analyte is absorbed onto the stationary phase to analyze the composition of the mixture. In general, HPLC guard columns in front of the analytical columns to extend and protect the service life of the analytical columns. The effect of HPLC guard columns is remove irreversible particles, pollutants and molecules from the column.
The most common HPLC column is made of stainless steel, it also can be made of thick glass, polymer(such as Polyether ether ketone), a combination of stainless steel and glass, or a combination of stainless steel and polymer. Compared with glass, stainless steel more corrosion resistance, high-pressure resistance, wear resistance, longer service life so which reduces the using cost. The length of typical HPLC Analytical columns is 3-25cm, the diameter is 1-5cm. Different from the HPLC columns, those columns usually are straight. The typical diameter of the packed column particles is between 3 and 5 µm. When the diameter of the particles accumulated inside the chromatographic column decreases, the efficiency of the liquid chromatographic column will increase.
Peak or peak broadening will reduce column efficiency. The ideal situation would be for sharp peaks to be resolved. The longer a substance stays in the column, the widen of the peak. Lengthen the HPLC column is a method to improve the separation of different substances in the column. UHPLCS column has advantage of high flow rate, smaller back pressure, little dead volume and reduce flow path diffusion.There are many specifications and sizes of UHPLCS HPLC columns, such as 4.6*50、4.6*100、4.6*150、4.6*250 and so on. 0.1um and 0.4um is optional.
Chromatographic columns usually need to be kept at a constant temperature to maintain efficiency. The height of the plate and the number of theoretical plates determine the efficiency of the column.Improving efficiency will be to increase the number of boards and reduce the height of the boards.
The number of boards can be determined by the following formula：
ñ=大号/ ħ（1）(1)N=L/H
L=length，H=height
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Post time: Dec-11-2020
