What's the different between paraformaldehyde and glutaraldehyde when they are used as fixers? I have prepared cell cover slides and fix them in 4% paraformaldehyde solution. Then 0.1% Triton-x 100 and DAPI were used for permeation and nuclear staining, respectively. However, the fluorescence of my samples were dramatically quenched. I could not find out the reason. I have noticed that glutaraldehyde was recommended after the staining of lysosome. I would like to know the difference between paraformaldehyde and glutaraldehyde.