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How to choose excitation light source for direct reading spectrometer?
Release time: 2019-12-20 10:42:17 Click: 992
，这些过程非常重要，是衡量元素含量是否准确的几个主要技术指标，如光谱分析的检出限，精密度和准确度等，只有放直读光谱仪的激发光源做好了，才能得到好的分析结果。 There is a partial excitation light source in the direct-reading spectrometer, which is responsible for several main processes such as vaporization, dissociation, and excitation of substances . These processes are very important. They are several main technical indicators that measure the accuracy of element content, such as the detection of spectral analysis. Limit, precision and accuracy, etc., only when the excitation light source of the direct reading spectrometer is completed, can good analysis results be obtained.
The excitation light source has two action processes. This role is to evaporate the sample and excite the atoms to produce a spectrum. These two effects take place simultaneously and jointly determine the intensity of the spectral line. The evaporation and dissociation of elements in the sample will involve the physical and chemical properties of the sample components. Excitation of the evaporated element atoms is naturally related to the nature of the light source generator, more precisely to the electrical characteristics of the generator, so it can be said that the excitation light source determines the spectral analysis method, so the understanding of the current status of the light source is What the spectrum worker needs.
Due to the wide variety of samples for spectroscopic analysis, different sample shapes, and difficulty in elemental excitation, it is very difficult to use an excitation light source to meet various analyses for different tasks. Therefore, various types of light sources have their own characteristics and application scope, and different types of light sources should be selected according to different analysis purposes.
The electric discharge characteristics are different from arcs. In the arc, the electrode material is vaporized into the arc column by heat, and is excited by the collision between the particles. Electric spark discharge is composed of a conductive pipe and an electrode material vapor jet fire moment. When the spark breaks between the electrodes, the gas is strongly ionized in the very thin conductive pipe formed between the electrodes. 10 °～ 10A/cm2，使管道具有很高的温度（10000℃以上）。 After the pipeline is formed, the capacitor discharges through the pipeline and releases a large amount of energy in a short time. The maximum current density can reach 10 ° ~ 10A / cm2, which makes the pipeline have a very high temperature (above 10000 ° C). After the pipeline is formed, it expands vigorously at a speed of 1 ~ 5000m / s, and the temperature before the shock wave drops rapidly, we can hear the crackling of the electric discharge.
After the electric flower breaks down, the voltage drops sharply, the current density decreases, and the nature of the light source actually turns into an arc. The capacitor releases a lot of energy in the area where the electrode surface contacts through the pipe, so that the electrode material appears as a luminous vapor jet, and its jet velocity is about 10cm / s, usually called a torch. Each discharge creates new pipes at different surfaces on both ends of the electrode. Therefore, torches are also generated at different surfaces. The diameter of each electric flower on the electrode is about 0.2mm. In the actual analysis, the exposure time is 1 ~ 2min, and thousands of breakdowns will occur. Therefore, the area of effect is not very small. Although the pipe temperature is very high, the electrode material is strongly scorched by the torch spray, but due to the area of each breakdown Not large, the time is short, the electrode head is not hot, and there is not as much material entering the discharge area per unit time as the arc.
How to choose excitation light source for direct reading spectrometer
From the perspective of quantitative analysis, the requirements for the light source are as follows:
1 . ppm 或 ppb 数量级。 The analysis sensitivity is high, and it can analyze trace and trace elements, and the sensitivity can reach the order of ppm or ppb .
2 . C 有小的变化时，相应的分析线强度 2 变化要大，即 dI ／ dc 要大。 The concentration sensitivity is high, that is, when there is a small change in the analysis element content C , the corresponding change in the analysis line intensity 2 is greater, that is, dI / dc is greater.
3 . In the excitation process, the light source should have good stability and reproducibility, which is the basic requirement to ensure the accuracy of the analysis.
4 . The matrix effect is small. When the matrix content in the sample changes, the results of the element analysis are not affected by the matrix change. The influence of the third element, the influence of the organization structure, the influence of the sample shape and quality should be small.
5 . ( 积分 ) 要短，可提高分析效率和分析速度。 The pre-ignition time and exposure time ( integral ) should be short, which can improve the analysis efficiency and analysis speed.