Question: Is a spectrophotometer able to detect contaminants and traces of heavy metals, like: Lead, Mercury, Cadmium, Chromium, Arsenic, Copper and Nickel? Which is the best method for continous tracking of contaminants in river water?

falbriard asked on February 11, 2019 17:41
105 | 1 answers | #18340


Checking for a software and IoT oriented solution that helps to monitor environmental conditions. Use spectrophotometry is one of those topics.



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First, using a spectrometer in the visible range ,by itself, normally isn't possible. You normally have to add chelating agents to make the metals visible and adjust the ph . Chromium might be an exception to this, depending on the detection limits.

There are standard methods for detecting metals in liquids. Check with the epa for the specific method. But they are rarely continuous. Usually, they require sampling the water and adding reagents for testing. Many also require moderately expensive equipment.


@Ag8n , Thanks for the reply. There might exist different view angle, about the challenge and ways to tackle the problem. Your answer is right, mentioning the standard process for chemical analysis, which certainly gives more precision about composition and dilution of contaminants. At the other side, lets think about a one step process, simply by measuring a water sample with precision and loading its data into a digital infra. Two ideas here:

What:
. If we add a mixture of chelants or other reagents prepared to match the known fingerprint of the contaminants, so that its spectral lines get visible in the VIS/UV spectrophotometer image?

. If we use more advanced algorithms for detection of emission & absorbance lines of chemical elements based on a database, much in a ways as practiced in astrochmeistry? Machine learning might also be helpful to raise precision.

Any thoughts on this how to improve the detection by use of contaminants in a simple IoT oriented process?

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You might be able to find some thing. Let's take it step by step. First, the only one of those metals that has any color in the Vis is chromium. Even then, you will probably need to get it to the same oxidation state. Cr(3) and Cr (6) absorb at different wavelengths. It might still be better to go with a cheating agent, even with chromium. The public labs spectrometer is visible only. That's not to say you couldn't extent the range. But it will take some extra money to do. For exsmple, the lamps commonly used are deuterium lamps, which are quite expensive. Having said that, there was an article on public labs about using tesla coils as a plasma source for other ga s lamps. That might be a way to generate a source of uv light.
Now, as to the astro stuff. The common methods on earth are atomic absorption(AA), graphite furnace AA, or a variation on inductively coupled plasma (ICP). These are usually ICP mass spec or ICP optical emission. These are abbreviated ICP/MS and ICP/OES. They are quite expensive. But, prior to the fourier transform revolution, most instruments were. Now, FTIR instruments have dramatically reduced the cost of those instruments. Anything I can do to help, let me know.


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