Fig. 5From: Quantification of plasmid DNA reference materials for Shiga toxin-producing Escherichia coli based on UV, HR-ICP-MS and digital PCRThe dPCR amplification curves of pStx2 before (a) and after (b) enzyme digestion. The relative fluorescence signal (ΔR) was automatically normalized by deducting the background of each chamber. The frequency represented the number of the PCR curves with a certain Ct valueBack to article page