First, what is aging?
First of all, we have to define what is called aging.
There are two cases. In the first case, the new column is usually aged before use. The main purpose is to remove the stationary phase that is not stable enough to make the new column more stable. In another case, a sample is made for a day, and there is a residue in the column. It is also said to age the column.
Second, what is the focus of aging?
The first focus of aging is temperature.
The maximum temperature for aging is usually recommended to be set to the middle of the method's maximum set temperature and column withstand temperature. For example, the maximum temperature of this method is 300 degrees, and the column's temperature tolerance is 325, which can be aged to 310 degrees.
However, it should be noted that different column tolerance temperatures vary widely. Columns with high polarity and high film thickness are usually resistant to low temperatures. For example, the DB-wax column has a constant temperature tolerance of only 250 degrees Celsius. If the film thickness is increased to 0.5 um, the withstand temperature will further drop to 240 degrees Celsius.
It is recommended that students carefully look at the column box or instructions before aging, because the use of the column above the upper temperature limit has a great impact on performance and life.
The specific aging process usually slowly heats up to the aging temperature, such as 2 to 5 degrees Celsius / min, and then continue to age for 2 hours.
Third, what is the most common cause of aging failure?
Avoiding the presence of oxygen is the most common cause of aging failure.
Because oxygen at high temperatures is a good catalyst for breaking chemical bonds, once the stationary phase in the column is oxidized, the bond between them will be destroyed, and the stationary phase will no longer be able to "fix" the column, causing a large amount of column loss. The efficiency of the column will also drop significantly.
From the perspective of avoiding oxygen, strict aging needs to pay attention to the following points:
First, extend the end of the column into the solvent to see if there are continuous bubbles. If not, check for leaks and the column is broken or clogged.
Second, before warming up, first pass the carrier gas for 15 minutes to replace the oxygen that may be present in the column.
Third, make sure other connectors are properly installed.
Fourth, do you want to connect to the detector?
In addition, when the new column is aged from the point of view of avoiding pollution, it is best not to connect the detector. If it is an FID detector, it can be used without ignition or hydrogen and air.
V. What should I pay attention to?
If it is a column that has already been used, it is afraid of residue, and it is desirable to remove contaminants by high temperature aging.
Some labs even run a aging method every day before shutting down, but this approach is actually risky. Because of this kind of pollution, it is often a compound with a high boiling point, which is usually concentrated in the column head, such as pigments, proteins, gelatins, etc. in the sample. Blind aging may promote the faster transfer of pollutants backwards, but not completely discharge the chromatogram. The column will instead contaminate the entire column.
The correct approach should be to analyze the composition and contamination of the sample first. If it is a component that has aging temperature and cannot be completely vaporized, such as pigment, protein, gelatin, etc., the column should be maintained before aging, including It is meaningful to change the liner and the column head to remove the pollution source and then aging.
Summary
The main points of aging include
1. View the instructions to determine the aging temperature
2, check the instrument connection to ensure no oxygen
3, it is best not to connect the detector
4. If necessary, do the inlet maintenance first.
5. Slowly heat up to aging temperature for 2 hours
(Content Source Chromatography)
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