Ethidium bromide breakdown - (Sep/21/2006 )
We are having problems with our ethidium bromide. After approximately 6 months our ethidium stains the gel with the same affinity as the DNA fragments. We end up having lots of background in our gel, and fragments are barley seen. Ethidium is stored in a dark place and 1.5ul of 10mg/ml ethidium in a 100ml gel. Why is this happenin?
I have been using the same bottle of EtBr (10 mg/ml) for years and have not had any problem. May be your solution is drying out and you ended up with adding more than you intended. That will give you high background staining and your bands seem to be weaker.
Maybe you're not adding enough EtBr. try 10ul of 10mg/ml per 100mg gel or add the EtBr to your buffer as well.
I always use 1.0ul of 10mg/mL ethidium bromide in a 100mL gel.
for me, in a time when i did bunches of gels, i added only 0.8µl of 10mg/ml EtBr. It was good too.
check the expire date of your EtBr.
if its alright try to change your gel and see whether high background remains or not.