i'm doing nested pcr. the first time i did it i had contamination in the negative control. i changed the taq (Hotstar), dNTPs, water and order new primers. i also cleaned the pipets, changed the tubes and the tpis (with filter).
it worked for a while but now i'm having the same problem. i always put the material in UV first. i have changed again the dNTP, water and made the primers from a new aliquote stock. the only thin i didn't changed was the taq (i did't have a new one). the problem continues!!! i made a 3 negative controls and only 2 were contaminated.
i'm getting frustated...
if you have any idea of what i can do to get rid of contamination please tell me. Thanks