Selection of pre-burn time and exposure time of Optical Emission Spectrometer

Do you know the choice of pre-burn time and exposure time for Optical Emission Spectrometer?  Regardless of the pre-ignition time or the exposure time, it is necessary to be cautious. In the analysis of the Optical Emission Spectrometer, the excitation of the sample requires a pre-ignition time.

The sample is excited in a spark chamber filled with argon, and most of the air is driven away, so the effect of selective oxidation and the effect of oxidative absorption of ultraviolet light in the excitation discharge are relatively small, but there are still complex physical and chemical processes.  Such as the process of evaporation and diffusion.  The Optical Emission Spectrometer must pass a certain period of time before it can reach a stable discharge, that is, the absolute intensity and relative intensity of the spectral lines of each element tend to be more stable. This process is called the pre-ignition stage.  But this process is shorter than in the air.  And for different steel types, the pre-ignition curves of different elements are different.  The Optical Emission Spectrometer 's choice of pre-burn time can be determined by trace method and integration method.  The tracing method is to make a pre-ignition curve for each element, taking into account the time for each element to reach stability, and determining a common pre-ignition time.  The integration method is to repeatedly excite the sample under different pre-ignition times and observe the reproducibility of the analysis results of each element, so as to select an appropriate pre-ignition time.  For low- and medium-alloy steels, the pre-ignition time is 4-6 seconds; for high-alloy steels, the pre-ignition time is 5-8 seconds; for free-cutting steel, the pre-ignition time is 10-30 seconds.  However, it must be pointed out that the length of the pre-ignition time is related to the performance of the light source. If the energy is large, the pre-ignition time will be shorter.  The determination of the exposure time mainly depends on the reproducibility of the elemental analysis in the excited sample.  The exposure process is a process in which the photocurrent of the Optical Emission Spectrometer charges the integration capacitor (also called integration).  The integration result can be considered as the average value of the photocurrent, so the integration time should not be too short.  In order to ensure the accuracy of analysis, the total number of spark discharges should be around 2000-3000 times.  Make the light intensity and ratio of iron and analytical elements moderate.  In normal analysis, the exposure time is generally 3-5 seconds.  However, it must be pointed out that the exposure time of the Optical Emission Spectrometer is related to the energy of the light source.