First of all, what is a mass analyzer. Gas chromatography-mass spectrometry is an analytical method for measuring the mass-to-charge ratio of ions (mass-to-charge ratio). The action of the accelerating electric field forms an ion beam that enters the mass analyzer. In the mass analyzer, the electric and magnetic fields are used to cause opposite velocity dispersion, and they are respectively focused to obtain a mass spectrum, thereby determining their mass.
The quadrupole is one of the most commonly used mass analyzers. The quadrupole mass spectrometer is a dynamic mass spectrometer. Since it only works with a pure electric field and does not need to involve a magnetic field, its structure is simple and the weight is light; it only requires the incident energy of the ions to be less than a certain upper limit, and does not require the incident ions to achieve energy focusing, so that the structure can be introduced. Simple, high-sensitivity ion source, suitable for ions with a certain energy dispersion, such as secondary ions; fast scanning speed, the sensitivity and resolution of the instrument can be adjusted by adjusting electrical parameters, and the same instrument can meet different analysis requirements. These advantages make the quadrupole attract much attention since its birth, and it has developed rapidly. At present, the quadrupole mass spectrometer technology is quite mature. As a compact, fully functional and low-cost mass spectrometry instrument, it has been widely used in the fields of physics, analytical chemistry, medicine, environmental science, and life science.
In actual use, two opposite electrodes among the four electrodes are connected together to form a pair of X electrodes and a pair of Y electrodes. The working power supply of the quadrupole electrode system is a so-called radio frequency power supply which contains both high frequency AC voltage and DC voltage components. When the positive and negative output voltages of the RF power supply are respectively loaded on a pair of X electrodes and a pair of Y electrodes, a quadrupole electric field distribution will be generated in the field space enclosed by the quadrupole electrodes. The motion of ions in a time-dependent quadrupole electric field is the basis for ion confinement and mass analysis at quadrupole electrodes.