Chromatographic parameters: Characteristic parameters of solute retention - an insightful description of column...

Previously introduced characteristic parameters of solute retention - the solute characteristic temperature (T_char) and thermal constant (θ) in GC as well as the characteristic solvent composition (ϕ_char) and the composition-constant (Φ) in LC - are described herein from a single perspective. Unlike conventional thermodynamic parameters, e.g., entropy and enthalpy of solute evaporation from stationary phase in GC that do not have a direct chromatographic meaning, the characteristic parameters do. Thus, T_char and ϕ_char are the column temperature and the solvent composition in GC and LC, respectively, at which the solute retention factor (k) is equal to 1. Quantities θ and Φ in GC and LC, respectively, are analogous to the time-constant in scientific and technical fields. Thus, e.g., Φ is the increase in the solvent composition leading to e-fold reduction (e ≈ 2.72) in k. Properties of characteristic parameters illustrating intuitive nature and simplicity of based on them concepts and equations are described.