Principle and Application of Plasma Coupled Mass Spectrometer

Principles of Plasma Generators

Plasma is a widespread state of matter in the universe. The sun is a huge plasma, and the ionosphere in the upper atmosphere of the Earth is also a plasma. In the sealed space there are three layers of empty quartz tube with an axis, the inner and outer layers are argon-filled, and the middle layer is the aerosol being examined. At a very low vacuum (at a certain air pressure), there are high-pressure electrodes near the nozzle, and the gap between the positive and negative electrodes is small. Under the action of a strong electric field, the gas is punched through, producing spark discharge. The working gas and the element tested are both in a highly ionized state, so the plasma is formed.The plasma has a temperature of 6,000-10,000 ℃, and the electrodes used are usually copper pipes or sheets with flowing cooling water inside.The electrical power required to produce the plasma is greater. The element being examined becomes a plasma state, usually a positively charged ion with a certain kinetic energy. Plasma is an electrically charged particle that flows in a direction and obeys the laws of electric and magnetic fields. For example, under an electric field, subjected to the force of Coulomb, When the magnetic field strength increases abruptly, the speed of rotation increases, and the speed of parallel advance becomes smaller, even zero, because the kinetic energy is constant.

Analysis Principles of Mass Spectrometry

The element being detected is a plasma state, i.e. an electrically charged particle with a certain electric charge, a definite mass, and a given kinetic energy. Therefore, measuring the charge-to-mass ratio can obtain the type of element, measuring its fluorescence strength information can obtain concentration information, measuring kinetic energy can obtain information on ion binding energy, which reflects the surface state information of the ion.

A spherical, centrally porous cathode is designed to be placed directly in front of the plasma flame. The positive ions of the examined element are attracted by the electrode with negative voltage, penetrate from the central pore of the electrode, and enter the mass spectrometer analyzer. The mass spectrometer analyzer consists of a designed constant electric and magnetic field, a plasma fluorescence observation screen, and a fluorescence strength analyzer. A constant electric field is generated between parallel electrode plates with a constant voltage difference, and a constant current passes through a copper-made spiral tube, where there is a constant electric field. The electric and magnetic fields can be superimposed, or the detected charged particles can pass through the electric field, enter the magnetic field, and finally reach the plasma observation screen. The electric field intensity E, the magnetic field strength B and the position of the particles on the screen can be used to calculate the charge to mass ratio and kinetic energy.

Sample preparation and application

The sample preparation is similar to that of AAS, AFS or AES. The standard sample preparation method is similar and the external standard method is used for calibration. The least square method is usually used for data processing. It is widely used in impurities analysis of pure metals, trace analysis of precious metal elements in mining samples and trace analysis for heavy metal elements in biochemical samples. Multiple elements can be analyzed at the same time, and the lower limit of analysis is up to ppb level (1 / 1 billion).