What is the role of the pretreatment column and the guard column of the liquid chromatograph?
The "columns" referred to in the HPLC include columns of various names such as an analytical column, a pretreatment column, a pretreatment column (Proecolumn), and a guard column (Guard column). Among them, the use of the treatment column and the guard column is for the purpose of protecting the analytical column. The name terms of the treatment column and the guard column are sometimes mixed, and the Shandong Luchuang analysis distinguishes it here.
What is the difference between the pretreatment column and the guard column of the liquid chromatograph?
In general, everyone knows about the structure of the gas chromatograph. The pretreatment column is placed between the pump and the injector, only through the mobile phase. The guard column is placed between the injector and the analytical column, through the mobile phase and the sample sample solution.
Why do you have to have a treatment column?
The pretreatment column was mainly used to saturate the stationary phase of the "liquid phase coated column" at the time of HPLC. Of course, this purpose is basically no longer used.
The purpose of using the pretreatment column is to remove insoluble matter or impurities in the mobile phase, and to protect the analytical column while using a mobile phase that tends to degrade the filler.
First of all, what is the so-called insoluble matter and impure substance contained in the mobile phase?
Various reagents are used in the mobile phase of the HPLC, in which some insoluble or impure substances are mixed. Most of the insoluble matter can be removed by filtering the mobile phase with a membrane filter, but very fine particles pass through the filter. In addition, after the mobile phase modulation, there is a possibility that insoluble matter or impurities fall from the air or the container, the human body, and the like. These insolubles and impurities may contaminate the column or cause blockage, or adverse effects on the analysis, depending on the purpose of the analysis. For example, when an inorganic monovalent cation is analyzed in ion chromatography, the polyvalent cation is not eluted according to its mobile phase conditions. Therefore, a large amount of polyvalent cations contained in the mobile phase are continuously trapped by the filler, and the maintenance of the monovalent cation becomes faster. At this time, it is possible to prevent the generation of the pretreatment column Shim-pack IC-PC1 with a large ion exchange capacity. Or in addition to the analysis of amino acids by postcolumn derivatization, the ammonia in the mobile phase causes a change in the baseline, which often hinders the detection of peaks. This can also be done by installing a pretreatment column that captures ammonia (Shim). -pack ISC-30) Get the reduction of the above situation.
As mentioned above, the pretreatment column can function as a protective column for the mobile phase which tends to deteriorate the filler. For example, a silica gel-based filler can be used in reverse phase chromatography to add a high concentration buffer to the mobile phase. In the case of an amine, an alkaline mobile phase or the like is used. We know that such mobile phase silica gel carriers will slowly dissolve. For this reason, the pretreatment column packed with the silica gel-based filler was installed to suppress the deterioration of the analytical column.
Why do you have to have a guard column?
The guard column acts as a pre-capture material that will be strongly adsorbed by the analytical column and cannot be washed by the mobile phase. The packing of the guard column is usually the same as the column for analysis, but it is not necessarily the case if the ingredients to be trapped are clearly known. The inner diameter should not exceed the analytical column, and a length of about 1 to 2 cm is sufficient. This is due to the fact that the damage to the analytical column is in most cases only a small portion of the packing on the inlet side of the analytical column.
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