Thank you Akdor. I have performed this assay and it has worked fine, I am just confused why some people go to the trouble of cloning. I know the molecular weight of my amplicon, and I can quantify how much purified product I have from a regular PCR so I can calculate the number of copies in my PCR-generated standard - i just don't see why you'd bother cloning it and using a plasmid which you'd then quantify and do the same calculation on anyway. Do you mean that it would achieve a more similar efficiency being plasmid associated than just a short amplicon? I can see that. Hmmmmmm!