Control in HPLC

Selectivity Control by Mobile Phase pH and Column Temperature These two parameters are of major importance for selectivity control in HPLC, especially with acidic and/or basic analytes. The charge state of analyte molecules influences both their hydrophobic (dispersion type) interaction, as well as possible ionic secondary interactions (e.g., with dissociated residual silanol group on silica-based stationary phases). The relatively wide range of so-called mixed-mode phases make very effective use of ionic interactions, but specialty phases are outside the scope of this chapter (refer to Chapter 4 for more information). 

---