Oxygen is a hazardous substance for most of the capillary columns. At room temperature, the column will not be damaged. But as the column temperature increases, the column will be severely damaged. It is important to be noted that polar GC columns will be severely damaged at low oxygen concentrations.
Apparent phenomena of oxidative damage and influence on analysis
● Influence on column efficiency
The column can still be used when it is not severely damaged, but column efficiency will be reduced.
Comparison of column evaluation report
Chromatogram after oxidative damage
● Influence on resolution
The column can not be used any more when it is severely damaged.
The reason for oxidative damage
In practical applications, there is no problem when columns contact oxygen in a short time(e.g. an air injection or quick release of the septum nut).
Leakage in the carrier gas pipeline is the “culprit” of column damage. As the column temperature increases, the stationary phase degrades rapidly, causing problems such as loss of stationary solution, reduction in column efficiency, and peak tailing. And if we find the symptoms of “small black spots” on the column, it has been severely damaged, which means the column is completely unusable.
Firstly, ensure that there’s no air leaks and no oxygen in the system, especially the polar columns (e.g. PEG20M and FFAP). And here’re the precautions during using below：
1. Focus on concentration of the carrier gas, the concentration of N2 is 99.999%, it is not recommended to use the generator as the carrier gas source;
2. installing the column, check whether the gas pipe or pressure gauge leaks, and do not analyse sample when the column and system leak;
3. During sample analysis and aging of the column, do not exceed the maximum operating temperature. Meanwhile, remember to ventilate for a period of time and then increase the column temperature. And we must ensure that the carrier gas is always stable during the analysis and aging process;
4. Change the injection septa regularly;
5. Replace the carrier gas cylinder in time;
6. Install the oxygen trap and replace it after it’s invalid.
Welch has been focusing on the development and production of GC columns for many years. Each column has been rigorously tested before released from the factory and has an evaluation report. It has a lot of advantage such as ultra inert, low loss, high efficiency, high selectivity, stable reproducibility and long life.
In recent years, Welch has launched some hot applications such as 22 organochlorine, 37 fatty acids and liquor content analysis. Because of excellent product performance and perfect after-sales support system, the Gas chromatography columns has been widely used in universities and research institutes, pharmaceuticals, petrochemicals, brewing, environmental protection, etc.
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