phantom band in DNA purification - A new band appears after purifying DNA from agarose gels (Aug/09/2002 )

We're using GFX Amersham's kit to purify DNA from solution and agarose gel bands. Although sometimes it works right, since few weeks to nowadays we're having some trouble. When we run the purified band in a new agarose gel, it appears a new DNA band, almost of half the weight of that purified, and our band becomes only slightly visible. We don't know if it's denaturation, secondary structure o contamination, but it happened to more than one person. It happens with all band sizes tryied. We don't know a possible explanation. Did it happened to anybody? Do you know a possible explanation, and solution?

We didn't have this problem with DNA, but especially with PCR amplicons. After purification we eluted in water. In most cases this gives other structures and therefor 2 bands. When we added a drop of Tris buffer pH 8 to establish a end concentration of 10 mM the products were run again on agarose and the problem was solved.

CBS, Utrecht, The Netherlands