We have performed the denaturation in FISH with normal formamide (73 C), but it seems that the probes did not attach to the chromosomes, there are only non-specific signals. I wonder whether it could be due to that formamide was not deionised?
You can do denaturation with normal formamide. I recommend keeping the formamide at -20C for long storage. Stocks solutions of denaturation solution can be made several weeks in advance. These should be stored at 4C until,