According to the working principle of modern spectrometers, spectrometers can be divided into two categories: classical spectrometers and new spectrometers. The new spectrometer is based on the modulation principle. The classic spectrometer is a slit spectrometer. The modulation spectrometer is non-spatial, and it uses a round hole to enter light. According to the spectral principle of dispersion components, spectrometer can be divided into prism spectrometer, diffraction grating spectrometer and interference spectrometer. OMA (Optical Multi-channel Analyzer) is a new type of spectrum analyzer, which integrates the functions of information collection, processing and storage, and adopts photon detector (CCD) and computer control. Because OMA no longer uses emulsion, it avoids and omits darkroom processing and a series of complicated processing and measurement afterwards, which fundamentally changes the traditional spectroscopy technology, greatly improves the working conditions and improves the working efficiency. Using OMA for spectral analysis, the measuring basin is accurate, fast and convenient, with high sensitivity, fast response time and high spectral resolution. The measurement results can be immediately read from the display screen or output by printers and plotters. At present, it has been widely used in almost all spectral measurement, analysis and research, especially for the detection of weak signals and transient signals. 4.2 Selection of dispersive elements and determination of optical parameters of spectrometer. 4.2. 1 Selection of dispersive elements of spectrum analyzer In the design of imaging spectrometer, the selection of dispersive elements is a key issue, and the advantages and disadvantages of prism and shed dispersive elements should be comprehensively weighed [140-al] The direct reading spectrum analyzer is a "Chinese-style" spectrum analyzer, and the operation is simpler and clearer. Discovery and scientific explanation of atomic absorption phenomenon in the first stage of the development history of atomic absorption spectrum As early as 1802, W.H.Wollaston discovered the dark lines in the solar continuous spectrum when he was studying the solar continuous spectrum. 18 17, J.Fraunhofer discovered these dark lines again when he was studying the continuous spectrum of the sun. Because the reasons for these dark lines were not known at that time, they were called Fraunhofer lines. 1859, when G.Kirchhoff and R.Bunson studied the flame spectra of alkali metals and alkaline earth metals, they found that the light emitted by sodium vapor would be absorbed when it passed through sodium vapor at low temperature. According to the fact that sodium emission line and dark line are in the same position in the spectrum, it is concluded that the dark line in the continuous spectrum of the sun is in the atmosphere around the sun. As a practical analytical method, the generation of the second-stage atomic absorption spectrometry started with 1955. This year, Australian Wals published his famous paper "Application of Atomic Absorption Spectrometry in Chemical Analysis", which laid the foundation for atomic absorption spectrometry. In the late 1950s and early 1960s, Hilger, Varian Techtron and Perkin-Elmer successively introduced commercial instruments for atomic absorption spectrometry, which developed the design idea of Valsi. In the mid-1960s, atomic absorption spectrometry began to enter a period of rapid development. See reference [1] for the generation of electrothermal atomic absorption spectrometer in the third stage. 1959, Lviv of the Soviet Union published the first paper on electrothermal atomization technology. The absolute sensitivity of electrothermal atomic absorption spectrometry can reach10-12-10-14g, which makes atomic absorption spectrometry a step forward. In recent years, with the development of Zeeman effect and self-priming effect subtraction background technology, atomic absorption spectrometry can be successfully realized in high background. On this basis, the matrix improvement technology, platform and probe technology and the application of stable temperature platform graphite furnace technology (STPF) developed can effectively realize the atomic absorption determination of many complex samples. Reference [2] The development of atomic absorption analyzer is in the fourth stage. With the development of atomic absorption technology, the continuous updating and development of atomic absorption instruments have been promoted, while other scientific and technological progress has provided technical and material basis for the continuous updating and development of atomic absorption instruments. In recent years, a microcomputer-controlled atomic absorption spectrophotometer has been designed by using continuous light source, step grating, light pipe and diode array multi-element analysis detector, which opens up a new prospect for simultaneous determination of multi-elements. The microcomputer-controlled atomic absorption spectrometry system simplifies the instrument structure, improves the automation degree of the instrument, improves the determination accuracy, and greatly changes the face of atomic absorption spectrometry. Coupled technologies (chromatography-atomic absorption spectrometry, flow injection-atomic absorption spectrometry) have attracted more and more attention. Chromatography-atomic absorption spectrometry (GC-AAS) has an important application not only in solving the chemical speciation analysis of elements, but also in the determination of complex mixtures of organic compounds. It is a promising development direction. Advantages and disadvantages of atomic absorption spectrometry

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