Properties of Analytes and Matrices Determining HPLC Selection

The main physicochemical properties of the analytes and of the matrix that are critical factors in selecting an HPLC method of analysis are discussed according to their role in separation and detection processes. Examples of physicochemical properties of analytes related to the separation are the following: the chemical composition and structure, acidic or basic character, isoelectric point, dipole moment, polarizability, hydrogen bonding capability, octanol/water partition constant, molar volume, solubility of nonelectrolytic compounds, van der Waals molecular volume, and van der Waals surface area. Among the most important properties for the analyte detection process and its selection are the following: UV-Vis absorption, fluorescence, chemiluminescence, refractive index, mass spectra, and electrochemical behavior. For the selection of the HPLC separation technique, the role of the chemical nature of the analyte, pKa in the case of acids and bases, octanol/water partition coefficient, and analyte concentration are emphasized. It is shown that the matrix chemical composition and amount of matrix must be taken into account for the selection of an HPLC separation.