Glow discharge spectrophotometry is a technique primarily used to study the elemental composition of materials. It has many applications in the material manufacturing industries, where it can be used to find out if any oxidation, surface treatment or contaminants are present in or on the sample.
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In this article, we discuss the principle behind the working of optical glow-discharge spectrophotometer, some of its practical applications as well as studies that have used the technology in innovative ways. Finally, we look at some of the drawbacks that are worth noting when considering technology in a workflow.
How does glare discharge optical emission spectrometry work?
A glowing discharge is a plasma that forms when an electric current passes through a gas. It is produced when a voltage is applied between the cathode and the anode in a glass tube containing a low pressure gas such as helium. This ionizes the gas so that it illuminates the tube with a bright light, which can be maintained when the applied voltage exceeds the striking voltage. The color of the resulting light is specific to the type of gas used in the tube.
The atoms and ions excited in the discharge plasma produce a characteristic emission spectrum for each element, and a single element can produce multiple distinct emission spectral lines which constitute the light produced by the discharge.
The glow-discharge optical emission spectrometer consists of a discharge lamp, an optical spectrometer, and a data detection and analysis system. The spectrophotometer is used to analyze the gas emission spectrum while the data detection and analysis system allows for quantitative and qualitative analysis of the interactions in the gas.
Magnetron discharge and radiofrequency discharge are the two most common glow-discharge plasma generators.
What are the practical applications and uses of glare discharge optical emission spectrometry?
If an elemental formation depth profile of a sample of up to 150 μm is required, glow-discharge photoemission spectroscopy is the technique used. This is particularly desirable for metals and insulators. It provides rapid elemental analysis, making it essential for quality control in steelmaking and aluminum metallurgy processes.
In the steel industry, for example, applications of glare discharge optical emission spectrometry have been reviewed. Processes such as passivation of stainless steel, phosphating on electro-galvanized steel substrate, comparison of two layers of coating on hot-dip galvanized substrate, quantitative carbon analysis of steel plate, aluminum surface separation in aluminum-transformed induced elastomer steel material, micro-gloss formation on aluminum-zinc coating, And check the color of the surface.
With this technique, it is possible to know the elements present in the sample and their concentration, and the composition of the sample with depth, which can help to know if there are any oxidation, surface treatments or contaminants present in or on the sample.
What are some advantages of glare discharge optical emission spectrometry?
The advantages of this method include the ability to analyze both surfaces and the bulk of the sample at great depths. The method can analyze up to 43 elements simultaneously, which include all metals, sulfur, carbon, oxygen, chloride, and hydrogen. This range generally ranges from hydrogen to uranium, although this depends largely on device configuration, detection limit for parts per million (ppm), and depth profiles ranging from a hundred nanometers to 150 micrometres.
It can be used to analyze both insulators and conductors, there is a high detection sensitivity, and the quantification is straightforward and simple with appropriate parameters.
Examples of using optical emission spectrometry for glare discharge
Al-Ghanbari et al., in a study published in the journal Electrical ECS messagesused a glow-discharge optical emission spectrophotometer to detect lithium deposition as a function of depth at graphite electrodes in postmortem analysis, where lithium deposition reduces cell integrity by causing rapid capacity decay.
Lithium coating was achieved by spinning commercial cells with graphite anodes at 5 °C. After formation, the interfacial graphite electrodes were compared to the solid electrolyte. Oxygen, lithium, and carbon depth profiles revealed surface effects varied in terms of thickness and lithium content, with the lithium deposition having a much greater concentration of lithium.
Using depth profiling, glow-discharge optical emission spectrometry was able to demonstrate lithium deposition on graphite anodes of Li-ion batteries.
Researchers have also sought to improve the technology to expand its use. In a study published in Analytical Atomic Spectrum JournalResearchers have developed a miniature, battery-powered optical emission spectrometer to measure minerals in water samples. There was no need to pre-treat the water samples, and this made it an environmentally friendly approach.
The device can test cadmium, mercury and lead simultaneously without separation or enrichment, with detection limits of 33-253 g/L (flow injection mode) and 7-92 g/L/ (continuous flow mode). The calibration curves for cadmium, mercury, and lead were linear for concentrations in the range 2-50 g/L. All approved reference materials, tap water and ocean samples have been tested successfully and with good accuracy.
What are some limitations of glare discharge optical emission spectrometry?
Glow discharge spectrophotometry is very effective in providing important information that helps in the processing of metals and insulators. However, it has two drawbacks.
This method is destructive, especially for soft materials such as polymers and biomaterials, as it requires evaporation of the sample. In addition, the configuration of the device can limit the number of detectable objects, does not provide for imaging, and there is still a need to provide appropriate parameters. Furthermore, the device is limited to atomic information and samples must be flat and vacuum compatible.
To summarize, glow discharge optical emission spectrometry provides a fast and reliable way to qualitatively and quantitatively analyze elements in samples. It provides high-quality data that can be used to improve the materials manufacturing process. Despite its limitations, avenues for innovative use and improvement of its capabilities exist.
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References and Further Reading
Azom. (2018). What is Optical Emission Spectroscopy (OES)? [Online]. AZoM.com. Available at: https://www.azom.com/article.aspx?
Ganbari, N.; Waldman, T., Casper, M., Axman, B. and Wohlfahrt-Mehrens, M. (2015). Detection of Li deposition by glow-discharge optical emission spectroscopy in a postmortem analysis. Electrical ECS messagesAnd the 4(9) p. 100. https://doi.org/10.1149/2.0041509eel
Peng, X., Guo, X., Ge, F. and Wang, Z. (2019). Portable battery powered optical emission spectrometer for battery operated cathode glow solution for environmental metal detection. Analytical Atomic Spectrum JournalAnd the 34(2) pp. 394-400. https://doi.org/10.1039/C8JA00369F
Xhoffer, C. and Dillen, H. (2003). Application of glare-discharge photoemission spectrometry in steelmaking. Analytical Atomic Spectrum JournalAnd the 18(6) pp. 576-583. https://doi.org/10.1039/B212750B