To keep the U(H)PLC method functional we have to look at all of those possible changes carefully. This is done with the DryLab 4 Modeling software, where we can test 3 levels of 6 factors, i.e., 3^6 =729 different variants of chromatograms in less than 30 sec. We can see the distribution of the critical resolution values, and have for each case a real chromatogram with a precision of MT 99% accuracy. We can also test which factor has the strongest influence on the results and change tolerance limits, the position of the working point to be able to keep "Out of Specification" (OoS) data to a minimum. We can optimize in this way the success in routine QC work and save with the new technique several weeks of work in multifactorial robustness work.