brass in contact with buffer

arvid

I have brass in contact with the buffer at one point in my system, and have noticed that it is getting darker over time. What kind of metals are in contact with the buffer in your systems? Brass? Stainless steel? Aluminium? Does anyone know how it is effected by the buffer, and how it effects ETC?

joelrosiene

At one point I had a bronze electrode nut open to the system. Very bad corrosion and blue residue was the result. Now I waterproof everything with a sealant that isn't platinum.

arvid

@joelrosiene, yeah I noticed that too, any conductive material (like a metal, except platinum) in contact the DC circuit and buffer will corrode very quickly because of electrolysis..

I was actually thinking about the buffer circulation as a whole - I'm guessing that most people's pump/water circulator will be stainless steel?
I'm also using a heat exchanger from a car to cool the buffer (heat exchanger is aluminium, so that's one more metal..)

arvid

Ok, after lots of frustration with yellowing of the buffer and tissue I did some tests exposing the buffer to various metals at 37 degrees celcius for a couple of weeks.

Conclusion so far is that air, nitrogen or oxygen doesn't seem to make any difference, brass is ok but aluminium turns the buffer yellow.

https://docs.google.com/file/d/0B9_6SmMpRj96NDd2ZnJrRG8yMWM/edit?usp=sharing

Also had trouble with my pump - it was a cheapish circulator for heating systems made out of cast iron and painted on the inside - it gave of a nasty brownish color that naturally spoiled both buffer and tissue quite quickly..

https://docs.google.com/file/d/0B9_6SmMpRj96cGIwUE1Wa1RiVkk/edit?usp=sharing

My current system is built around a LKB Bromma 2219 Multitemp II (about $500 on ebay). It can run for a week without a n y discoloring of the buffer (haven't tried longer). As far as I understand stainless steel is the only metal in contact with the buffer.

Hoping someone can learn from my mistakes

daj1u06

Just a quick question to those of you who use a stainless waterbath to hold the bulk buffer, rather than a sealed container sitting in it - surely as this buffer is in direct contact with the buffer in the chamber, therefore it and the stainless waterbath are therefore electrically "live" during a run? Normal electrophoresis systems have all kinds of interlocks in place to stop physical contact with the buffer during runs. How do you get away with it? (or haven't your safety officers seen what you are doing?).