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The gas chromatograph inlet septum is referred to as the injection pad and is one of the key components for introducing the sample into the column in the gas chromatograph analysis test. During the gas chromatograph injection process, the sample to be tested can flow through the column with the gas flow only when the carrier gas pressure in the column reaches a certain height. Here, the role of the injection pad is to keep the gas chromatograph system in a sealed state, to separate the sample flow path from the outside to prevent air from entering the system or sample leakage, and to keep the internal pressure of the chromatographic system stable.2ml gas chromatography vials
The injection pad is generally made of silicone rubber with high temperature resistance and good air tightness. The standard for selecting the inlet septum is usually based on the upper limit temperature detected by the gas chromatograph. In general, the lower temperature limit of the sample pad is softer and has better sealing, which is higher than the upper temperature limit of the same type. Compared with the pad, the puncture resistance (injection) is good. However, if the injection pad is used above the recommended temperature, the sample pad will leak or decompose.
The injection pad is a lossy accessory in the gas chromatograph analysis system. After a period of use, there may be air leaks or other abnormalities. The injection pad is damaged as follows: 1 Injecting gas leakage, during the gas chromatograph detection injection process, the injection needle will cause a certain degree of damage to the injection pad and leaking; 2 decomposition, the column is separated When some high boiling point samples are tested, the column temperature will be relatively high. At this time, the sample pad will be slightly decomposed under high temperature conditions; 3 sample loss, once the sample pad is damaged, the sample will be lost; 4 column The internal flow rate is reduced and the efficiency of the column is decreased. When the injection pad leaks or is decomposed, the pressure inside the column is unstable, so that the carrier gas flow rate in the column is lowered, and the column separation degree is lowered. 5 The peak is abnormal, once the chromatogram The column separation is affected, the electrical signal of the substance detected by the detector is not accurate, and the formed chromatogram is abnormal, forming a ghost peak.2ml gas chromatography vials
The performance of the injection pad affects the accuracy of the gas chromatograph test results. Therefore, when the injection pad is damaged, it should be replaced in time. When should the gas chromatograph injection pad be replaced? In addition to the above phenomenon, you can also use the TCD detector to detect, in the case of no injection, there are regular small peaks on the recorder, indicating that the gasket leakage has been replaced. Replace the septum so that it is not too tight. Generally, it will be at normal temperature when it is replaced. It will be tighter after the temperature rises. If the septum is tightened too tight, it will cause difficulty in injection and it is easy to bend the syringe needle.
Although the injection pad is a small accessory in the chromatographic analysis, it can reduce the damage caused by a little attention during use. How to solve the unnecessary loss of the injection pad?2ml gas chromatography vials
1. Use in the high temperature range of the septum. The injection pad is generally made of silicone rubber. Silicone rubber has higher heat resistance than ordinary rubber. It can be used almost at 150 degrees without performance change. It can be used continuously for 10,000 hours at 200 degrees. It can also be used for a while at 350 degrees. Therefore, the selection of the injection pad must take into account the high temperature upper limit of the sample analyzed by the gas chromatograph, and try to use it within the temperature limit to avoid overheating decomposition;
2. Try to use an autosampler to reduce damage to the injection pad;2ml gas chromatography vials
3. Use a sharp-pointed syringe to reduce the area of force;
This is the end of the introduction of Gas chromatograph injection pad replacement requirements. I hope it can help you.
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