Re: [plots-waterquality] Polarimetry for Water Analysis?

[Stevie Lewis]

Hi Jesse,

Just found this! looks really interesting. Want to post it out as a Research note on Public Lab? Also looping in the spectrometry group, think people there would be interested in your idea.

Best!

-Stevie

On Thu, Mar 23, 2017 at 10:37 PM, Jesse S <jesse....@gmail.com> wrote:

Hello Everyone,

Today I was in Industrial Chemistry learning about polarimetry.  For those who aren't familiar with it, there's a good explanation at ucla.edu.  The basics are that some chemicals rotate light waves that pass through them.  By polarizing the light before passing it through a sample, then viewing the light through a rotatable polarizing filter on the other side, a measurement of the rotation of the light can be made.  This is useful because the more concentrated the solution, the more rotation you get!  Here is the image from the ucla.edu page linked above:

Our professor brought out an ancient polarimeter that I'm pretty sure had a candle holder for the light source at one time, and I immediately began trying to come up with a way to make a digital one that would be useful and more portable.  I ran through a few iterations in my head using things like accelerometers for measuring the angle and a lux sensor for detecting the peak orientation of the polarizing filter and therefore the angle of rotation.  In an effort to reduce complexity and add the potential for autonomous operation I realized I could just use a servo connected to either of the polarizing filter assemblies.  This would provide a known degree of rotation to compare to the lux readings.  If used with a continuous flow sample tube, it would also allow for continuous readings of the flowing liquid.

Anyone think this would be of use in the field or have any experience with polarimetry? I don't know enough about it yet to know how useful it would be at detecting contaminants.  Another interesting option is that it might also give a rough assessment of turbidity with some calibration.

Does anyone have any suggestions for an inexpensive way to make the tubes with glass ends on them for samples?  They are quite expensive, and would likely cost as much as the rest of the device would.

I would love to collaborate on this if anyone is interested.

Jesse

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[Mathew Lippincott]

Jesse,

If you need a watertight tube with glass on both ends, consider looking at custom flashlight parts suppliers.  You can buy modular tubes, ends, and glass bezels. 

I'm not endorsing this site, but I've ordered some parts from here. There are other sites like it:

https://www.fasttech.com/category/1699/flashlights--lasers

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