RPLC of intact proteins using sub-0.5 μm particles and commercial instrumentation

This paper addresses whether one can gain an improvement in speed or resolution with a silica colloidal crystal (SCC) of nonporous 470 nm particles when using a commercial nano-UHPLC. Compared to a capillary packed with nonporous 1.3 μm particles and the same C4 bonded phase, the peak width for BSA is decreased by a factor of 6.8 for the SCC. Some of this improvement is attributable to slip flow since the ratio of particle diameters is only 2.8. Resolution in protein separations was compared for a 2-cm capillary of SCC vs a 5-cm column of porous 1.7 μm particles. Both used a C4 bonded phase, and on-column fluorescence detection was used for the SCC. Split flow (5:1) before the SCC decreased the gradient delay time to 0.4 min and the injected volume to 0.4 nL. For variants from the labeling of BSA, the SCC had a 5-fold higher speed and 2-fold higher resolution than did the commercial column. For a monoclonal antibody and its aggregates, the SCC had a 3-fold higher speed and a 3-fold higher resolution compared to the commercial column. The SCC gave baseline resolution of the monomer, dimer and trimer in 5 min. The results show that a significant advantage can be gained using a commercial instrument with the SCC, despite the instrument not being designed for use with such small particles.