Second, the standard or sample is best dissolved with the mobile phase (excluding special circumstances), can avoid a lot of trouble.
Third, to warm the column, the purpose of temperature increase, in part to increase the solubility of the solute, but more importantly, reduce the viscosity of the solvent, thereby improving peak shape and resolution. Note: Increasing the temperature will reduce the retention time, which also has an effect on the resolution. The temperature change has a great influence on the band width, and the height of the plate is affected by the temperature, although it depends on the type of chromatography used, and the temperature rises. Always reduce the height of the tray.
Fourth, the column temperature of the C18 column should generally not exceed 40 degrees Celsius, otherwise the fitness phase will easily fall off.
5. Injector use, except for washing with water each time, after a period of time, it is best to use methanol or acetonitrile repeatedly to pick up and clean.
6. When using HPLC for analysis, the retention time sometimes drifts, sometimes it changes rapidly. What are the reasons? How to solve it?
A: About the drift problem:
1. The temperature control is not good. The solution is to use a constant temperature device to keep the column temperature constant.
2. The mobile phase changes. The solution is to prevent evaporation, reaction, etc. of the mobile phase.
3, the column is not well balanced, the column needs to be balanced for a longer time
Seven, on the issue of rapid change:
1. The flow rate changes. The solution is to reset the flow rate to keep it stable.
2. There are air bubbles in the pump, and the air bubbles can be driven out by exhausting.
3. The mobile phase is not suitable. The solution is to change the mobile phase or mix the mobile phase in the control room.
8. What is the cause of tailing or double peaks in liquid chromatography?
1. If the sieve plate is clogged or the column fails, the solution is to back up the column, replace the sieve plate or replace the column.
2, there is interference peak, the solution is to use a longer column, change the mobile phase or replace the selective column
9. What is the main reason for nonlinear shunting when splitting with capillary chromatography?
1. The temperature of the injector is too low, the vaporization of the sample is incomplete, and a grading split occurs.
2. The temperature of the injector is too high, some components may be thermally decomposed, and some samples may be catalytically decomposed, or the sample may be partially adsorbed on the inner surface of the injector.
3. The sample was not evenly mixed or insufficiently mixed before the split point.
4, the system's injection pad, column joints and other places leak.
Ten, doing analysis by liquid chromatography, column pressure is unstable, why? How to solve?
A: The reasons may be:
1. There is air in the pump. The solution is to remove the air from the pump and degas the solvent.
2. The proportional valve fails and the proportional valve can be replaced.
3. The pump seal is damaged and the gasket can be replaced.
4, the bubble in the solvent, the solution is to degas the solvent, if necessary, change the degassing method;
5, the system leak detection, find the leak point, seal it.
6. Gradient elution, where pressure fluctuations are normal.
11. How to prevent tar-like pollutants from entering the capillary column when doing PGS/MS analysis?
A: Polymers, especially those containing nitrogen, sulfur and halogens, often have tar-like substances. In order to prevent the tar-like substance from entering the capillary column and causing pollution, the performance of the column is lowered. The protective pre-column can be used, that is, a pre-column is connected between the cracker and the capillary column, and the tar-like substance is retained by controlling the temperature of the pre-column. In the pre-column, the pre-fill can be placed in the GC gasification chamber, which is easy to control the temperature and reduce the dead volume of the system. Of course, the pre-column packing needs to be replaced frequently.
Twelve, I recently replaced another grade of ODS column, although the separation is still possible, but the retention time can not be reproduced, why?
A: This is because the analyte may have the ability to form hydrogen. Liquid Chromatographs Although the manufacturing technology of fillers has been greatly improved over the past few years, the concentration of silanol groups on the surface of ODS fillers varies from manufacturer to manufacturer. It is these silanol groups that may interact with the sample. Therefore, the relative retention times of the components in the same analyte on different grades of ODS columns may be different. The addition of a small amount of competitor, such as triethylamine (TEA), to the mobile phase will saturate the bonding ability of the silanol groups, thereby ensuring good reproducibility of relative retention times on different grades of columns.
13. What is the service life of high temperature capillary columns?
A: The life of the capillary column depends on the performance of the column itself, depending on the use, such as the temperature of use, the state of the sample, the amount of injection, etc. If the sample is clean within its temperature range, the column is not In the case of pollution, the life of the column is generally between 2 and 3 years.
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