Spectro won't help (lots of proteins, detergents...).
Right, I don't want to do anything with the DNA afterwards, I just need a control of the DNA content for normalization purposes (I can't use total protein content). We had no linearity and an extremely poor sensitivity with the dyes we tried so far (EtBR, Hoechts, DAPI, DRAQ5). Most likely interference form the detergents...
I just found out that PicoGreen might work. It's apparently very sensitive...