I've been looking absolutely everywhere for something like this and I think I've got everything I need already sitting here to pull this off! Paper link!
On closer look this isn't exactly what I was looking for, but I think that I can use this as inspiration because their goal is different than mine and they demonstrate how remarkably flexible C-18 and HPH fractionation can be. They essentially elute their peptides off of immobilized C-18 and pull the supernatant as the fractionated. Super cool, right?!? Sounds a little complex, but they boost their peptide coverage of interest from low sample volumes, so there are applications for this kind of fractionation for sure.