Re: [DIYbio] Re: Cheap capillary electrophoresis

Optical is more expensive for sure. When I looked at it, it would cost more than $100 for each, diode and detector. UV lens is also a problem (glass needs to be UV transparent) but I found a neat paper how to make one from pdms. I bought an old spectrometer and used its lamp and detector with this pdms lens. Got the signal when I tested concentrated dye, but it was very weak. Later I figured that I should have removed the capillary coating. So sensitivity may be better for optical but cost-wise, alignment wise (aligning UV optical path is a dangerous and hard thing) , stability is better for capacitance sensing. Capacitance also has its problems, I later figured that I stray currents from HV can mess up the circuit so better electrode geometry and enclosure would help. Unfortunately, I have to do other things now and the electrophoresis will have to wait. 

On Wednesday, May 3, 2017 at 9:00:38 AM UTC-5, John Griessen wrote:
On 05/03/2017 08:52 AM, Gordana Ostojic wrote:
> Here is one


Hello Gordana,
You said about harristotle1's video:

 > I can't see from the video the other end of the tube and if that is in liquid. Anyway I did use similar thing (it's somewhere on
 > this board). It turned out that optical detection is hard (material issues with UV, lamps are expensive, power is demanding...) so
 > I found out most people work with dielectric detection.

Are you sure optical detection is still "hard" today?  How did you do the dielectric detection?  Measure capacitance of the
capillary circuit?

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