High-throughput determination of adsorption equilibria for chromatographic oligosaccharide separations

Adsorption equilibria of the saccharides d-glucose, d-galactose, l-arabinose, lactose and a sugar acid were measured on gel-type sulfonated poly (styrene-co-divinylbenzene) strong cation exchange resins in a high-throughput (HT) 96-well plate batch uptake mode using a pipetting robot at 25 °C. Four different ionic forms, Ca2+, K+, Na+, and H+ were used. Single component adsorption isotherms were determined in a concentration range of 10–240 mg ml−1. Multicomponent experiments were performed to investigate competitive adsorption in a concentration range of 10–120 mg ml−1. A qualitative investigation on competitive and cooperative effects was performed. All sugar isotherms showed a linear behavior except for the sugar acid which showed an unfavorable (anti-Langmuir) behavior in the high concentration ranges. Selectivity values were determined from the binary mixture partition coefficient (K) values of each component. This HT 96-well plate batch uptake method proves to be less laborious and consumes less time and material compared to the frontal analysis and adsorption–desorption methods where column experimentation is used. Ternary mixture separation of arabinose and the sugar acid from glucose showed K+ and Ca2+ loaded resins having the best selectivity (DIAION Ca2+ 2.01 and 1.78 for l-arabinose/d-glucose and sugar acid/l-arabinose respectively), similarly Purolite K+ loaded resin for the lactose separation from glucose and galactose (1.17 for lactose/d-glucose). Column experiments were performed to validate the batch uptake experiments. The static binding results could easily be translated to the column experiments with good agreement. Finally, adding to the validity of the approach, binary and ternary fixed-bed experiments were well described by a dynamic mathematical chromatographic model using the parameters obtained from the binary-component isotherm data.