Gradient elution separation and peak capacity of columns packed with porous shell particles

The separation of the tryptic digests of myoglobin and bovine serum albumin were carried out in the gradient elution mode, using water, acetonitrile and TFA as the mobile phase components and columns packed with a new type of shell particles, Halo C18. These particles give very high efficiencies, characterized with an unusually low eddy diffusion contribution and a small mass transfer contribution. However, because the molecular diffusivities of the peptides in the digest are small, the mobile phase velocity corresponding to the optimum velocity for maximum efficiency is also small, of the order of 0.3 mm/s. The gradient slopes also must be small. Peak capacities of 400 were achieved, with analysis time of the order of an hour.