Hi all,

I was transferring yesterday, as usual, using our old transfer buffer (1X Tris base glycine with 20% methanol) and saw these yellow particles formed on top of the layer of foam at the end of the transfer. The transfer buffer was cold but had turned yellow.

However, one of the lab personnel used the same buffer before I used it and it worked just fine. I used the same sponges, cassettes and buffer he used for mine. After he used the buffer, it was clear (I checked it before and verified after by checking up on the remaining buffer that I didn't use) and when I started the transfer the voltage was not different from any other time.

To give you some more details on what we use;

We pour these large 12% gels (15 cm x 15 cm and 1.5 mm) to achieve better resolution.

The transfer is done at constant current of 1.75 A for 1 h 30 min. I usually cool down the transfer buffer at -20C for two hours (I didn't do it this time!) and the transfer apparatus is kept in a cold water bath filled with ice packs to keep the temperature as low as possible.

I have never seen this before and I suspect the old transfer buffer could be the culprit here. However, how could it change so drastically from morning to afternoon? Does anyone have an explanation on what those yellow particles are?

I really appreciate your input on this and my apologies for the detailed question.