Mini diaphragm pumps are widely used in the gas chromatography industry
Background information:
Gas chromatography was first introduced in the 1950s. It is a new separation and analysis technology. Based on the differences in the physical and chemical properties of the components, the separation of the mixture is achieved by using the differences in the boiling point, polarity, and adsorption properties of the substances. It is a major scientific and technological breakthrough and is widely used in many fields.
Petrochemical analysis industry: (1) Crude oil analysis; (2) Oil product analysis; (3) Analysis of sulfur and nitrogen-containing compounds; (4) Analysis of aliphatic hydrocarbons and aromatics, etc.
1)Environmental analysis: (1) air pollution analysis (toxic and harmful gases, gas sulfides, nitrogen oxides, etc.); (2) water resources (including organic pollutants in fresh water, sea water, and wastewater); (3) soil analysis, etc. (organic pollutants, solid particulate waste).
2)Food analysis industry: (1) analysis of pesticide residues; (2) analysis of food additives; (3) analysis of volatiles in packaging materials, etc. Pharmaceutical analysis: (1) Analysis of amino acid derivatives in blood; (2) Analysis of some volatile drugs, etc.
Application introduction:
1.Principle of gas chromatographic separation：
The difference in boiling point, polarity and adsorption properties of substances is used to separate the mixture. After the sample to be analyzed is vaporized in the vaporization chamber, it is brought into the chromatographic column by an inert gas (ie, carrier gas, also called mobile phase), and the column contains liquid or solid (stationary phase), each component in the sample has different boiling point, polarity or adsorption properties, and each component tends to form a distribution or adsorption equilibrium between the mobile phase and the stationary phase.
Due to the flow of the carrier gas, the sample components are repeatedly distributed or adsorbed/desorbed during the movement. As a result, the components with a high concentration in the carrier gas flow out of the chromatographic column first, and the components with a high concentration in the stationary phase are distributed. The components flow out afterward. When the components flow out of the column, they immediately enter the detector. Detectors can convert sample components into electrical signals, and the magnitude of the electrical signal is proportional to the amount or concentration of the component being measured. When these signals are amplified and recorded, it is a gas chromatogram.
2.The main process of gas chromatographic separation：
1) Gas sampling system: use the carrier gas to load the gas to be detected. The carrier gas is mostly inert gas, such as nitrogen, argon, helium, etc., which is loaded by a mini diaphragm pump and output with a stable pressure to drive the sample to flow in the chromatographic column, and push the separated components to the detector.
2) Separation system: The sample to be analyzed is brought into the chromatographic column by the carrier gas, and the column contains a liquid or solid stationary phase. Due to the differences in the boiling point, polarity, adsorption and other factors of each component in the sample, each component is different. It tends to form a distribution or adsorption equilibrium between the mobile phase and the stationary phase. The component with a high concentration in the carrier gas flows out of the column first, and the component with a large concentration in the stationary phase flows out after the distribution, that is, the separation of the components is completed. .
3) Detection and recording system: The components flowing out of the chromatographic column enter the detector for detection. There are many types of detectors, and the commonly used ones are hydrogen flame ionization detector (FID), thermal conductivity detector (TCD), nitrogen and phosphorus detection Detector (NPD), Flame Photometric Detector (FPD), Electron Capture Detector (ECD) and other types have different structures and principles. Some use ionization ion current detection, and some use component thermal conductivity difference detection. Some use the combustion to make the component emit light through the wavelength to detect, so the detection of different components needs to correspond to different detectors.
Application Difficulties:
1. The output flow of the carrier gas pump needs to be stable to ensure the stability of the group injection volume.
2. The mini diaphragm pump will bear a lot of pressure in the gas circuit, so it is necessary to ensure the stability of the mini diaphragm pump and the consistency of parameters under different pressure fluctuations.
3. Some detectors will radiate heat to the surroundings (such as FID) during work, which is easy to form a higher temperature environment in a narrow space, and the mini diaphragm pump needs to be able to work stably in a higher medium or ambient temperature.
Solutions:
D35 series compressor mini diaphragm pump
The micro compressor can generate negative pressure at the suction port to inhale gas, and apply a positive pressure at the exhaust port to discharge gas. It is suitable for scenarios that require positive pressure output, gas circulation, etc.
1. Small size, stable flow rate, reinforced nylon and EPDM rubber material, good resistance to corrosive medium;
2. The parameters have high consistency, and can work stably under harsh working conditions such as high-temperature environments and transmission of high-temperature gases;
3. The use of non-interference brushless motor will not affect other interference sensitive components of the equipment;
4. The suction port and exhaust port of the mini diaphragm pump can carry a large load, so there is no fear of pressure fluctuations caused by the front-end and back-end processes of the equipment.