THE SPATIAL-DISTRIBUTION OF POLY(METHYLOCTYLSILOXANE) DEPOSITED BY SOLVENT EVAPORATION IN THE PORES OF HPLC SILICA PARTICLES

Poly(methyloctylsiloxane) (PMOS), sorbed into the pores of HPLC silica particles by solvent evaporation, can function as a useful stationary phase for reversed-phase chromatography The present work addresses th e question of how the PMOS is distributed in the pores. Measurements o f the surface area (BET, N-2) of a series of partially loaded samples (0-40 % PMOS, m/m) using a typical batch of HPLC silica (10 mu m irreg ular particles with 6 nm pores) show that the specific surface area of the samples decreases linearly with the specific loading (mass of PMO S per gram of silica). This result is not consistent with a ''film'' m odel in which the PMOS is deposited uniformly on the pore walls, but i s consistent with a model in which long segmented ''plugs'' of PMOS ar e deposited within the pore system.