Since the advent of atmospheric pressure ionization (API) interface technology, liquid-mass coupling has been developed rapidly. Liquid mass coupling technology is the combination of liquid chromatography and mass spectrometry, which not only reflects the high separation performance of liquid chromatography, but also reflects the powerful identification ability of mass spectrometry. It has indelible advantages in analysis and detection, and the detection sensitivity of most substances exceeds other methods, so it has been widely used in many fields such as biochemical analysis, drug and food analysis. Demand drives innovation, mass spectrometer has also experienced rapid development, such as quadrupole mass spectrometer, quadrupole ion trap mass spectrometer, time of flight mass spectrometer and ion cyclotron resonance mass spectrometer.

The principle of liquid-mass coupling is to separate the liquid phase of the substance and then through the mass spectrum detector for analysis. The liquid phase separates the liquid and molecular state of the substance, through the mass spectrum heating and high voltage ion source, so as to transform into gas phase charged ions, at this time if there is high purity nitrogen, can accelerate the solvent evaporation in the ion source, promote the formation of gas phase charged ions, play the role of dry gas. In triple quadrupole mass spectrometry, high purity nitrogen is used as collision gas and also collides and breaks ions, so as to facilitate the formation of quantitative ions for the compounds to be analyzed.     For example, the liquid gas supply of AB includes Gas1Gas2, Curtain gas, exhaust gas. Gas1 is atomizing gas, whose function is atomization and solvent removal. Gas2 is an auxiliary gas, which is used to form charged ions in the gas phase. Curtain gas is curtain gas, which prevents neutral molecules or small droplets from entering the mass analyzer and reduces background noise. exhaust gas is used for exhaust gas.

At the beginning, liquid nitrogen was the main source of nitrogen for liquid-mass combination. Although nitrogen produced by liquid nitrogen has a high purity, it also has some shortcomings, such as impossible removal of hydrocarbons, containing a certain amount of water, inconvenient transportation and ventilation, and risk of frostbite. There are two main reasons why people do not choose the nitrogen generator at first: first, worry about the purity; Second, the cost is higher. However, with the continuous development of science and technology, there are some excellent national brands in China. The products produced by these enterprises are sold without tariffs, agency fees and other costs, which are more used to improve the quality of products. In addition, according to the characteristics of high humidity and dirty air in China, local conditions are produced according to local conditions. Since then, the psychological change of nitrogen generator in mass spectrum users began. The basic newly purchased mass spectrum will be directly equipped with a generator, and the previous mass spectrum will gradually replace the liquid nitrogen tank with a nitrogen generator.