Gas chromatographic analysis instrument use and maintenance
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Gas chromatography manufacturers produce a wide variety of products, mainly consisting of five parts: pneumatic system, injection system, separation system, detection system, and data processing system.
1, pneumatic system
The pneumatic system includes a carrier gas cylinder, a hydrogen generator, an air generator, and a flow regulating valve. The entire gas path system requires pure gas and continuous operation, and the flow rate should be stable, the airtightness is good, and the flow rate is accurate.
(1) The total valve and pressure reducing valve of the carrier gas cylinder should pay attention to frequent leak detection (using soap water or detergent water leak detection method), the carrier gas purity requirement is >99.99%, and the damage of the column will be accelerated when there is oxygen;
(2) Pay attention to the timely replacement of the carrier gas cylinder, the total pressure of the cylinder should not be lower than 2.0MPa.
(3) When using a hydrogen generator, it is necessary to observe that the liquid level is between the lowest and highest liquid levels, and not lower than the minimum liquid level, in order to prevent damage to the electrolytic cell, and the drying tube should be replaced periodically.
(4) When using the air generator, the drying pipe should be replaced regularly; after the generator is turned off, the air pressure should be released in time to protect the compressor.
(5) The regulation of the pressure regulator valve, the steady flow valve and the needle valve should be slow.
2, the injection system
The injection system includes a syringe, an injection septum, and a glass liner. The contamination and damage of each component can affect the chromatographic results.
3. Separation system
The main component of the gas chromatograph separation system is the column, which is the “heart†of the gas chromatograph. Its main function is to separate the mixed components in the sample into a single component, so as to qualitatively and quantitatively different components. Detection, the performance of the column has a very significant impact on the test results, so the correct use and maintenance of the column is the most important use of the gas chromatograph.
3.1 Column installation
When installing the column, pay attention to the length of the column entering the inlet end and entering the detector end. Cut the column with a special ceramic or steel blade, and the slit should be flat. The nut at the joint should be loose and appropriate. Leakage is not too tight and damages the graphite gasket. When cutting and installing the column, pay attention to the bending angle to avoid scratching or even breaking the column.
3.2 aging of the column
The new column must be aged before it can be used. After long-term use, the column with reduced column efficiency also needs to be aged. The column that has been removed for a long time from the instrument needs to be aged before it can be reused. 
4, detection system
The function of the gas chromatograph detector is to convert the information of the chemical components that are separated by the separation of the column into electrical signals, and then qualitatively and quantitatively determine the composition and content of the separated substances.
5, data processing system Chromatographic data processing work has two major functions of data processing and software functions, is the automatic control of the chromatograph, to achieve qualitative and quantitative processing of the collected chromatographic peaks and issued a test report.