Re: [DIYbio] electrophoresis... path length design strategies

Well I cut 3 strips of filter paper and put them on glass slides.  Soaked one in salt water, one in 1x TAE, one in 10x TAE.


All read way too high on the multimeter for resistance until I got to the 200k and 2 million Ohm setting.

I tried to keep the probes 1cm apart but came to realize it didn't really matter.  In general I could get a resistance reading of around  1.5 million in the 10x buffer, and 500-800k in the 1x buffer.  I don't really remember what the salt water was.

It was never consistent really and seemed to fluctuate sometimes, and other times fluctuate a lot less, and stay in a consistent range.  Honestly no idea what to take away from it...not a nice solid # like a regular resistor would be.

On Thu, Jan 31, 2013 at 7:09 PM, John Griessen <john@industromatic.com> wrote:
On 01/31/2013 09:46 AM, Dakota Hamill wrote:
Let's say we have a piece of filter paper 10cm long, 1 cm wide, and 0.1 cm thick.

Is it wrong to think it could handle similar voltages and currents that an agarose gel could?
No, that sounds plausible/possible.

Say it was running at 100V and 0.050A.  Could you then use V=IR to calculate the resistance of the buffer soaked paper would be
2000 Ohms?

Or, via P=IV, P = (0.050A) x (100V) = 5W

Yep.  That's plausible/possible.  A 5Watt rated resistor is only 1 com long and .4 cm diameter
and it can get warm to hot at 5W, but not char to black.  A 10 cm long strip 1cm wide might
be barely perceptibly warm in still air while dissipating 5W since its surface areas are so
much greater.  Your guess at resistance could be way off, since gel boxes aren't so skinny
as you described.  What if The 5 Watt level happened at a current of .005Amp? then the
Volts would need to be 1KV.  I think that might be more normal for a 10X long as it is wide
gel or paper/electrolyte.

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