Field of Science

Why does white gunk develop on the anode?

 

The gunk is soft, almost-gel-like.  In the photo it's sitting in lumps in the buffer in the bottom tank, but only because I gently scraped it off the anode wire with a spatula after I took the gel plates out of the apparatus.  The anode was clean before I ran the gel.

The gel buffer was TBE with 10 mM MgCl2 added; might this be Mg(OH)2?

Later:  The white gunk is alkaline and dissolves in acid but not alkali.  It's not from the gel.  It also appeared when I ran a test minigel using TAE buffer with 10 mM MgCl2 added.

5 comments:

  1. No SDS; this is a simple DNA gel.

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  2. What is the anode material? It could also be a variety of chloride species, as the positive electrode can get oxidized, and then combine with Cl-. Thus, depending on anode material, I would guess you either have Mg(OH)2 or M(Cl)x, where M is the anode metal, and would only be likely if it is silver...

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  3. Are you sure it's not just pieces of the gel itself?

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  4. I've seen this before. It's definitely related to the Mg. I used to run lots of gels in TBM (Tris, borate, MgCl2) and they'd always have that build-up on the anode wire. But only when Mg was included; never otherwise.

    Don't worry about it. We ran literally hundreds of such gels in mini-gel rigs and never had any problem with the stuff. Didn't see any sign that it ate up the anode, e.g.

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