A Fast and Effective Method for Packing Nano-LC Columns with Solid-Core Nano Particles Based on the Synergic Effect of Temperature, Slurry Composition, Sonication and Pressure.

Nano-LC columns of different lengths (14–35 cm), 75 μm i.d., were packed with solid-core C18 particles using a conventional HPLC system at low pressure (375 bar) and without expensive tools and fittings. Solid-core particles consist of a solid, non-porous core surrounded with a shell of a porous layer with a very narrow particle size distribution. This geometry allows a faster diffusion of the analytes compared to porous particles, reducing the C term of the Knox plot. Different slurries of packing material were evaluated and tested. The packing procedure was carried out at room temperature and at 70 °C to evaluate the influence of this parameter on the overall process. The synergic action of pressure, temperature and sonication contributed to columns of various lengths in the packing process. The columns were tested at room temperature taking into account the following parameters: Knox plots, specific permeability and peak capacity. Reduced heights of theoretical plates, h, ranged between 3.8 and 5.1 at ν between 2 and 6. An LC-MS test was carried out with a Direct-EI LC-MS instrument.