Development of comprehensive two-dimensional HPLC for high-performance separations in the future

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The objective of this research project was to increase peak capacity of HPLC by developing simple and comprehensive two dimensional (2D) HPLC. By employing a monolithic silica-C18 column at the second dimension (2nd-D), we were able to obtain the following results.(1) We proved the concept of simple and comprehensive 2D-HPLC in a reversed-phase-reversed-phase mode by using a particle-packed column of fluoroalkyl-bonded silica as a first-dimension (1st-D) column, and C18- or pentabromobenzyloxypropyl-bonded monolithic silica as a 2nd-D column.(2) By utilizing the difference in selectivity provided by organic solvents, 2D-HPLC was carried out using monolithic silica C18 columns both at 1st-D and at 2nd-D.(3) 2D-HPLC was carried out by using an ion-exchange column packed with polymer particles at 1st-D and a monolithic silica-C18 column or a monolithic silica capillary column at 2nd-D for peptide separations.The use of these systems produced (1)peak capacity of up to 1100 in methanol-water mobile phase, (2)peak capacity of 700 or greater for hydrocarbons and benzene derivatives, respectively. The ion-exchange-reversed-phase 2D-HPLC system provided (3)peak capacity of 700 or greater for BSA digest with a short monolithic silica column at 2nd-D, and peak capacity of about 500 for BSA digest by using a 0.2 mmlD, 10 cm long capillary column at 2nd-D, respectively. Optimization of 2D-HPLC conditions were attempted to show the possibility of achieving peak capacity of greater than 2000 in one hour. The flow rate, retention factors of solutes, and column length at 2nd-D were shown to dominate the peak capacity of a 2D-HPLC system. Monolithic silica columns were found to be best suited for 2D-HPLC based on their high permeability and high performance at high linear velocity of mobile phase.