Public Lab Research note


$0.75 lead testing color strips

by warren | April 18, 2014 22:41 | 1,776 views | 5 comments | #10328 | 1,776 views | 5 comments | #10328 18 Apr 22:41

Read more: stable.publiclab.org/n/10328


Ok -- how does this work and can we DIY this?

2014-04-18_17.19.22.jpg


5 Comments

It is possible to recreate. This particular kit looks like it uses sodium rhodizonate. However all that is necessary is something that reacts with lead to make a colorful, insoluble precipitate

The following article details some of the chemistry and chemicals involved, and refers to a lab book that is very good that also has a lab based on the same topic: http://makezine.com/laboratory-198-analysis-of-paint-sa/

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I wonder how reliable these test strips are for lead; I've heard that some of the less expensive colorimetric techniques like this are pretty unreliable when assessing arsenic and mercury levels. Then again, even if this method isn't great at providing absolute concentrations, it might still work well as e.g. a binary indicator ('some of contaminant X is present' or 'there is no contaminant X present') ...

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Wow, mrericsully - interesting. Is sodium rhodizonate toxic itself? Could any be obtained easily and safely to make such strips ourselves?

I also like the use of white vinegar for dissolving lead that may be in soil or dust.

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The sodium rhodizonat isn't toxic according to the SDS I just looked at. The cost of the chemical itself might be a little prohibitive, but searching for it I stumbled across a YouTube video on making a related chemical potassium rhodizinate, which would do the same thing, since it is the rhodizinate anion that is important for the reaction and not the alkali metal cation: https://www.youtube.com/watch?v=BLmycZ2nrt0 . There are of course, other colored lead precipitates which although they'd probably be more cost effective and/or easier to obtain.

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Hi Don - why would they be unreliable; false positives? Poor calibration? Any links I could read up on?

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