Effectiveness of the H-root method for determining adsorption isotherms of protein-salt systems in open micro-channels

The application of the H-root method (HRM) for predicting isotherm data for protein-salt systems in open-channel chromatographs is presented. HRM mainly consists of performing a regression of the chromatographic response of a system in order to predict the isotherms of the solutes. The method is applicable to proteins with Type I (Langmuir) isotherms. HRM enables a quick determination of the effects of salt on protein isotherms, to facilitate the development of preparative separation protocols of trace proteins in open micro-channel systems. Two configurations were investigated: micro open parallel plate system (microOPPS) and micro open tubular system (microOTS). The effectiveness of HRM was evaluated by simulating the behavior of these open-channel systems with mass-transfer effects included. The influence of operating and geometrical parameters was determined with a detailed parametric study. It was found that HRM can give good estimates of the adsorption isotherms in both micro-channel systems. This is primarily attributed to efficient mass transfer, which ensured correspondence to the equilibrium assumption of HRM. In general, the microOTS was found to give more accurate predictions than the microOPPS. This is attributed to the smooth circular perimeter of flow. Nevertheless, the difference in accuracy is generally insignificant, and with the proper selection of operating conditions, both systems are well suited for HRM.