Analysis of Cyclic Adenosine Monophosphate (cAMP) Separation via RP-HPLC (reversed-phase high-performance liquid chromatography) by the Moment Method and the van Deemter Equation

The moment analysis of cyclic adenosine monophosphate (cAMP) was performed using chromatograms that were obtained with the pulse input method from an octadecyl silica (ODS) high-performance liquid chromatogra- phy (HPLC) column. The general rate (GR) model was employed to calculate the first absolute moment and the second central moment. Three important coefficients for moment analysis, which are molecular diffusivity (Dm), external mass transfer coefficient (kf), and intra-particle diffusivity (De), were estimated by the Wilke-Chang equation, Wilson-Gean- koplis equation, and comparing van Deemter equation to theoretical plate number equation, respectively. Experiments were conducted by various conditions of flow rates, methanol volume ratio of the mobile phase, and solute concentra- tion. After the moment analysis, results were organized by van Deemter plots. Also van Deemter coefficients were com- pared each other to effect Hax, Hf, and Hd on height equivalent to a theoretical plate (HETP, Htotal). The value of intra- particle diffusion (Hd) was the primary factor which makes for HETP whereas external mass transfer (Hf) was disre- gardable factor.