Unless otherwise specified, the LC column stock is the mobile phase shown in the evaluation report. Before use, it is important to note that the liquid chromatography column's stock solution is miscible with the mobile phase of the sample to be analyzed. In reversed-phase chromatography, if a high concentration of salt or buffer is used as an eluent, it should be transitioned with a low concentration of about 10% organic phase eluent, otherwise the salt in the buffer is easy to precipitate in the high concentration of organic phase and block the column.
There are several reasons why the LC column can cause the column pressure to increase
1. Pretreatment of mobile phase.
Impurities clog the column inlet filter, causing the pressure to rise. This is often caused by the mobile phase being unfiltered, or filtered but not filtered, allowing solid impurities to remain on the filter plate.
2. Precipitation of the sample.
When the solvent of the dissolved sample is not consistent with the mobile phase, the sample enters the column and can sometimes precipitate due to reduced solubility, resulting in increased pressure.
3. Precipitation of crystals.
When using a buffer-containing mobile phase, inorganic salts in the buffer may remain in the system, and they can precipitate due to reduced solubility in the new mobile phase, resulting in increased fluid resistance and increased pressure.
4. Bacteria or mold breeding.
Mold grows in the mobile phase, in the tubing, or at the inlet of the column and clogs the filter plate, resulting in increased pressure. Therefore, when using phosphate buffers, it is generally necessary to prepare and use them on the spot.
5. Solute adsorption.
When solutes are strongly adsorbed on the column and the mobile phase used is difficult to elute, the accumulated uneluting solute can also cause increased resistance and increased pressure.
6. The mobile phase is changed too quickly.
When changing the mobile phase system, the non-* change causes different immiscible mobile phases to exist in the same system, which will also cause the pressure to increase.
7. Pressure pulse.
During operation, there are sometimes sudden increases and decreases in pressure within the system. The pressure pulses thus formed can cause the collapse of the porous packing and small changes in the structure of the column bed, and the long-term accumulation of microchips in the packing may also increase the resistance of the column bed, resulting in an increase in pressure.