What’s the application of Micro diaphragm gas pump in a gas chromatograph?

GC is a common separation technique with the principle of separating the compounds and measuring their relative content in the gas phase. The separation principle of GC mainly includes the following points: the target compound interacts with the carrier gas. In GC, the substance to be separated is usually mixed with one or more gases to increase the volatility of the sample and the efficiency of separation. These gases are often referred to as the carrier gas phase or the mobile phase. The material to be separated will have some effects with the carrier gas phase, such as adsorption, dissolution or diffusion, which will have an effect on the transport rate and relative distribution of the material in the column. Distribution of matter in filled columns, where GC columns are usually composed of filled material, used to separate different compounds. The transport of compounds in columns is influenced by certain factors such as column length, filling material type, temperature and flow. The distribution of matter in the pillars needs to be determined by calculation and modeling. Detection of the substance in the detector, eventually, the substance will enter the detector for testing, and its concentration and relative content will be determined according to the sensitivity and measurement range of the detector. There are many types of detectors, including flame ionization detector, thermal conductivity detector, electronic capture detector, mass spectrometry detector, etc. Choosing different detectors can determine the content of specific compounds. Using the boiling point of the material, polarity and adsorption properties to achieve the separation of mixture, to analyze the sample in the vaporization by inert gas (carrying gas, also called mobile phase) column, the column contains liquid or solid (stationary phase), the components of the sample, polarity or adsorption performance is different, each component tend to form a distribution or adsorption balance between the mobile phase and the stationary phase. Due to the flow of the carrier gas, the sample components are repeatedly distributed or adsorption / desorbed in the movement. As a result, the components with large concentration in the carrier gas flow out of the column first, and after distributing the components with large concentration in the fixed phase. When the components flow out of the column, it immediately enters the detector. The detector is able to transform the sample components into electrical signals, the size of which is proportional to the amount or concentration of the components tested components. When these signals are amplified and recorded, it is the gas chromatogram.

Main flow of GC separation

1. Gas intake sample system: load the gas to be detected with the carrier gas. The carrier gas is mostly inert gas, such as nitrogen gas, argon gas, helium gas, etc. It is loaded and output puts stable pressure through the pump to drive the sample to flow in the column and push the separated components into the detector.

2. Separation system: the sample to be analyzed by carrying gas into the column, the column contains liquid or solid of fixed phase, due to the sample of boiling point, polarity, adsorption factors, each component tend to form distribution or adsorption balance between the mobile phase and fixed phase, in the load gas concentration component first out column, and in the fixed phase after the component concentration, complete the separation of components.

3. Detection recording system: chromatographic column outflow components into the detector, detector types more, commonly used hydrogen flame ionization detector (FID), thermal conductivity detector (TCD), nitrogen and phosphorus detector (NPD), flame luminosity detector (FPD), electronic capture detector (ECD), different structure, principle, using ionizing ion current detection, using component thermal conductivity difference detection, using combustion component emission through the wavelength, so detecting different components need to correspond to different detectors.

Difficult application of micro diaphragm gas pump in gas chromatography

1. The output flow of the gas carrying pump needs to be stable to ensure the stability of the group sample intake.

2. The micro diaphragm gas pump will bear large pressure in the gas circuit, so the stability and parameter consistency of the pump under different pressure fluctuations.

3. Some detectors will radiate heat to the surrounding area (such as FID) when working, which is easy to form a higher temperature environment in a narrow space, and requires the pump to work stably in a higher medium or ambient temperature.

4. Micro-diaphragm air pumps are particularly susceptible to ambient temperature during use. The high ambient temperature will lead to the high internal temperature of the gas pump, which will affect the gas transmission effect, resulting in the failure and burning phenomenon of the gas pump. And the ambient temperature is too low will lead to the freezing phenomenon inside the gas pump, resulting in the reduction of the gas transmission effect, and even damage the gas pump. To solve this problem, we can change the working environment of the gas pump, such as increasing the heat dissipation device of the gas pump, to ensure that the ambient temperature is appropriate.

5. Micro-diaphragm air pumps are also susceptible to gas pressure. When the intake pressure and the outlet pressure of the air pump do not match, the pressure inside the air pump is often unbalanced, which leads to the failure of the air pump and the operation difficulty. To avoid this problem, it is recommended to adjust and adjust the pressure of the air pump before using the micro diaphragm air pump.

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