Agarose gel electroforesis buffer

[Yap Yun Kiam]

	We have been using Tris-Acetate-EDTA (TAE) buffer for 
electrophoresis of Agarose gel for DNA samples. Previously, a problem 
occured in which our 1kb DNA marker bands either appeared as smear ( as 
if degraded) or there are a lot of stray bands. First, we check the 1kb 
marker and found that it is okay (let another lab try it). We tried to 
trace out the culprit, and finally we change all the TAE buffer (TAE is 
prepared in 10x stock and diluted before used). we suspect something went 
wrong with the buffer but we can't tell what went wrong. Recently, this 
problem re-occured, the 10x TAE buffer is not a newly prepared one, half 
of it has been used without any problem. We thought that it could be the 
deionize water that is used to dilute the 10xTAE, so we change all the 
deionize water in the lab and collect some fresh one (from the same 
deionize machine) but the problem still persist.

	Can someone suggest what the culprit is? How it can be solved?