Diffusion and Equilibrium Adsorption Coefficients of Aromatic Hydrocarbon Species in Capillary Columns

This study focuses on a mathematical description of elution of aromatic species in a 30 m×0.25 mm×0.25 μm BPX5 capillary column. Experimental studies involve the detection of chemical species at the capillary column outlet. Using the recorded peaks, statistical moments of different orders are calculated for both toluene and naphthalene. Modeling studies involve a laminar flow model with an equilibrium coefficient (Ks) and a solute diffusion coefficient in the stationary phase (Ds). Model validation is developed by performing experiments at different carrier gas velocities and GC oven temperatures. Under the conditions, neither the first statistical moment (M1) nor the second statistical moment (M2) is affected by the carrier gas velocity. Thus, the interface equilibrium coefficients (Ks) and the diffusion coefficients (Ds) solely depend on the solute and the capillary column polymer coating properties. Furthermore, the statistical moments of different orders show that the proposed interface equilibrium based model in the “narrow bore” 30 m×0.25 mm×0.25 μm BPX5 capillary column is adequate for aromatic species such as toluene and naphthalene.