Analysis of R-Limonene separation in RP-HPLC (reversed-phase high-performance liquid chromatography) by Moment method and Van Deemter equation

The moment analysis of R-limonene was implemented using chromatograms that were obtained with the pulse input method from an octadecyl silica (ODS) high-performance liquid chromatography (HPLC) column. The particle diameter of the stationary phase was 5 µm. The general rate (GR) model was employed to calculate the first absolute moment and the second central moment. Two important coefficients for moment analysis, molecular diffusivity and external mass transfer coefficient, were estimated by the Wilke-Chang and Wilson-Geankoplis equations, respectively. The intra particle diffusivity was obtained by comparing theoretical plate number equation with the van Deemter equation. Experiments were conducted by varying flow rate, volume ratio of the mobile phase, and solute concentration. After The moment analysis results based on the experimental elution curve, van Deemter plots were drawn. And van Deemter coefficients were compared each other in order to investigate the effects of H ₐₓ, H f, and H d on Height equivalent to a theoretical plate (HETP, H ₜₒₜₐₗ). Intra-particle diffusion (H d) was the most dominant factor contributing to HETP, while external mass transfer (H f) was negligible factor.