Handbook of Size Exclusion Chromatography and Related ...

same pore volume, large-pore particles are more brittle than those with small pores.
Operation under HPLC conditions requires that the particles withstand the high
pressures required for packing. Although small-particle SEC packings are usually
operated at low linear velocity, silica-based columns must be packed at relatively
high pressures to ensure physical stability of the column. Figure 8 shows the
results of a simple test to determine the pressure at which particles fracture (62).
The experiment was performed with a constant pressure pump. After filling the
column for 5 minutes at 3000 psi, the pressure was increased in 1000 psi
increments to 12,000 psi, at which point the hysteresis was determined by
lowering the pressure to 4000 psi. Note that the relationship between flow rate and
pressure for 100 A ˚ Supelcosil LC-Si silica is linear over the entire pressure range,
but that the pressure–flow rate curve for LiChrospher Si-100 starts to deviate from
linearity at 6000 psi. Flow rates at higher pressures are lower than expected, and
Figure 8 Stability of HPLC silicas during column packing. Packing materials, 2.25g of
5mm Supelcosil LC-Si and 1.35g of 5mm LiChrospher Si-100; columns, 15cm 4.6mm;
extension, 10cm 4.6mm; slurry reservoir, 35mL; Haskel pneumatic amplifier Model
DSTV-122C; slurry and driving solvent, methanol; see text for details.
© 2004 by Marcel Dekker, Inc.