Question: Arc Emissions- What electrodes to use?

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m3sca1 asked on September 15, 2016 02:06
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The question refers to using an electric arc to excite the sample. Obviously the choice of electrode will add to the spectra... Has anyone here tried using an arc? I figure DC would move material from one electrode to the other, adding more electrode material into the arc and contaminating or swamping the sample emission. AC arc seems like a logical choice, the second part to this question is what choice of material to use for the electrode to minimise peaks? Considering carbon rods, Tungsten welding TIG rods, any advice on this would be helpful.

Background story

The reason for joining this community came about from a friend asking about a cheap way to test for Lead contamination in cheap Knock Off toys. Spectrometry seemed like a good choice and the USB webcam Spectro' was a quick easy fun build that shows plenty of promise. With the sample being plastic and the target/sample emission spectra being Lead the obvious considerations are will the Lead be hidden by the emission from the electrode, and can an arc be easily setup so others may take advantage of this method. I have some ignition coil drivers that could serve as the High Voltage source, that just leaves choice of electrode.



2 Comments

Hi, this seems like it could be dangerous, and I don't know much about it. But are you talking about this: https://publiclab.org/notes/bwilliams/10-9-2012/carbon-arc ?

Do you know that there's a visible range (400-700nm) emission spectrum from lead, and do you have any link or reference to an example of that kind of analysis to base your research off of?

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Hi Warren, Thanks for your concern-the carbon arc you show in that video is quite a bit larger than what I had in mind but yes that sort of spark gap arrangement. The spark gap power supply is painful but not deadly, there is also the obvious danger of Lead poisoning. Yes I am aware of the visible emission spectra of Lead in a flame or arc. I have no links or references to base research on. I have experience with UV/Vis spectro's but never done any flame emission, but I am confident a low cost method can be devised.

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