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Your location: Home > Related Articles > Interpret which extrinsic factors affect spectral analysis

Interpret which extrinsic factors affect spectral analysis

Author:QINSUN Released in:2023-06 Click:132

1. Argon
The main function of argon blowing is to drive air out of the spark chamber when the sample is excited, and to reduce air absorption in the spectral lines of the ultraviolet region. The main reason is that the oxygen and water vapor in the air have strong absorption bands in the far ultraviolet region, which have a great impact on the analysis results, and are not conducive to a stable excitation, formation or strengthening of diffusion discharge and white spots when excited. In addition, the alloying elements in the sample can chemically react with the components in the air to form molecular compounds under high temperature conditions, so the analytical spectrum will interfere with the atomic spectrum we need. Therefore, the purity of argon must be required to reach more than 99.999%. In addition, the argon pressure and flow rate havealso a certain influence on the quality of the analysis, which determines the impact capacity of argon on the discharge surface. The foles rmed oxides are washed away, and these oxides condense on the surface of the electrode, thus inhibiting the continued excitation of the sample; excessive flow of argon gas causes unnecessary waste. Second, the spectrometer is also damaged. Therefore, the pressure and flow of argon must be appropriate. According to practice, the pressure and the flow of argon must be adjusted according to the different materials. For the analysis of low and medium alloy steel, the argon pressure input to the spectrometer should reach 0.5-1.5 MPa and the dynamic argon flow should be 12-20 readings. The static argon flow is 3 to 5 readings.
2. Slit
The spectrometer uses a complex and sensitive optical system. Ambient temperature, humidity, mechanical vibrations and changess atmospheric pressure of the spectrometer will cause slight changes in the spectral lines and cause spectral line shifts. Changes in atmospheric pressure and humidity will alter the refractive index of the medium, thus shifting the spectral lines. Increased humidity will not only increase the refractive index of air, but will also corrode optical parts, reducing the light transmission of the instrument. Humidity Generally, it should be controlled below 55% to 60%. The influence of temperature on the grating mainly changes the grating constant, changes the rate of angular dispersion and produces a drift of the spectral lines. These changes can cause the spectral lines to not be perfectly aligned with the corresponding exit slits, thus affecting the analysis results. Therefore, the optical system should be adjusted at least once a day,if the indoor temperature is kept constant. Adjust the slits twice a week, even if the weather doesn\'t change much.
3. The entrance window lens The lens leading to each chamber, especially the lens leading to the air chamber, due to the argon blowing when the sample is excited, the dust generated during the exposing the sample is blown towards the lensIt prevents light transmission and affects the accuracy of measurement results. Therefore, it must be cleaned frequently, usually twice a week, to keep it clean and to ensure that all light passes through the objective and enters the light chamber for measurement. It is specially reminded that after cleaning the lens, a few more waste samples should be excited, and the standardized operation should be performed after the intensity is stable, otherwise the analysis quality will be impaired.fected.
4. Excitation table
The cleaning of the inner surface of the excitation table is mainly to prevent the discharge of dust remaining on the inner wall from affecting the analysis results. Usually it needs to be cleaned every 100-200 excitations. The distance between the electrode and the excitation surface should be in accordance with The pole distance should be tightly adjusted. If the distance between the electrode and the excitation surface is too large, the sample will not be easily excited. If the distance between the electrode and the excitation surface is too small, the discharge current will be too large during exposure, so that it does not match the instrument parameters, and the measurement results will be There is a difference between the actual result and the accuracy of the measurement. Therefore, the distance between the electrode and the excitation surface must be precisely adjusted, and this problem must be taken into account.n counts after cleaning the excitation table and electrodes.
5. Correcting the working curve
Although the photoelectric direct reading spectrometer method is not limited by the photosensitive plate, once the working curve is drawn, the curve will change after a while . For example: lens contamination, electrode contamination, temperature and humidity changes, argon influence, power supply fluctuations, etc., can all cause changes in the curve. The position of A in the original graph, after a period of time the curve may drift to the position of B. In order to use the curves for analysis, we must try to bring the curve B back to the position of curve A. For this, the work curve must be normalized. The following points should be considered when calibrating the curve:
1) After cleaning the platform of excessitation of the sample, it must be stimulated more than 10 times or the argon gas must be passed for one hour before the daily calibration work can be completed.
2) The standardized sample should be uniform, the sample should be carefully prepared, the sample surface should be flat, and the texture should be clear. The analysis gap is accurate and the sample holder is kept clean.
3) The frequency of standardization is determined by the number of samples analyzed. Generally, normalization should be performed twice a day.
6. Control sample
In the actual work, due to the difference in the metallurgical process and some physical states of the sample and the standard sample, the work curve often changes. Usually the standard sample is mainly forged and rolled. The manufacturing status, while the daily analysis is the casting status. In order to avoid influence of the sample on the analysis results due to the change of the metallurgical state, a check sample with the same metallurgical state and the same physical state as the analysis sample should be used to check the test results. \'analysis. The element content of the control sample should be within the content range of the working curve, and the closer the content of the analysis sample, the better. At the same time, the element content of the control sample should be accurate and reliable, the composition should be evenly distributed, and the appearance should be free from physical defects such as pores, blisters and cracks.
7. Sample
The quality of spectral analysis results is highly dependent on the sample, and particular attention should be paid to sample preparation and processing technology. Due to pore segregation, the impossibility of obtAnything on a flat surface where the sample is not placed correctly, as well as errors caused by operational errors, will have a significant impact on the quality of the analysis.

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