I haven't seen much success with double barrel type chromatography in a while -- but here is a demonstration of a successful application in ultra low levels.
Setups like this are jus as fun to set up as they look, but the idea is that you are trapping your peptides on trap number 2 while your peptides are eluting off of analytical column #1. When everything goes onto column 2 trap and analytical columns number 1 are re-equilibrating. The goal is to wipe out that downtime between injections. The results are often having two distinct sets of files with very different looking chromatography, but this group seems to have the recipe for sorting it out!