Hello,

In qPCR, is there an optimal concentration for primers with a total volume of 20ul per reaction?

Thanks for your answer in advance!

What qPCR kit (or just enzyme) do you use? It depends on both the primers in question (how easily do they form primer-dimers) and the enzyme used, however I generally used 250 nM (for both the forward and reverse primers). Optimal primer concentration can only really be obtained by titration, but I have only done this (once) when initial results were dubious/contained primer-dimer peaks (increasing annealing temperature wasn't really viable/did not help either). When titrating, Thermofisher (Sybr Green) recommends checking the 100-500 nM primer range, however other researchers sometimes check between 50 nM and 900 nM (as of researchgate). 

https://www.thermofisher.com/nl/en/home/references/protocols/nucleic-acid-amplification-and-expression-profiling/pcr-protocol/sybr-greener-qpcr-supermix-universal.html