Does DEPC harm RNA?
FAQ ID -529

Trace amounts of DEPC will modify purine residues (A+G) in RNA by carboxymethylation. Therefore, residual DEPC must always be removed from solutions or vessels by autoclaving or heating at 100°C for 15 min. Carboxymethylated RNA may be translated with low efficiency in cell-free systems. However, its ability to form DNA-RNA or RNA-RNA hybrids is not seriously affected unless a large fraction of the purine residues have been modified.