Determination of the specific pore volume of chromatographic silicas by desoption of excess liquid

Author(s)

Dione Rodrigues Amgarten

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2006-11-05

Examining board members

Kenneth Elmer Collins; Marina Franco Maggi Tavares; Carla Beatriz Grespan Bottoli

• Advisor: Kenneth Elmer Collins

Abstract

The determination of the specific pore volume (sV) of chromatographic silicas of the type used in HPLC is important because the sV is a fundamental characteristic of the silica which relates directly to parameters (pore size and surface area) important to chromatography applications. The determination of sV is usually made by means of adsorption/desorption of nitrogen at low temperature (~75K) or of intrusion of mercury at high pressure. The instrumentation for these procedures are quite expensive, and require well trained operators. Therefore, the objective this project was to developed a relatively fast and reliable procedure, of low cost that could be accomplished at any laboratory by students or technicians with a minimum of special training. Starting with a volumetric adsorption procedure published in the literature a new gravimetric desorption procedure was developed which uses the same sample several times (recycling) to obtain statistically confident determinations. The influences of the humidity and of the choice of volatile liquid used in the desorption from silica were evaluated. The results show that, independent of the volatile liquid used, the sV value is precise and in close agreement with values obtained by the conventional instrumental procedures. The procedure requires about 6-8 hours to make 1-5 determinations in parallel. The procedure can be employed in a laboratory environment with neglible interference from ambient humidity. Comparisons with the other procedures show thet the sV values obtained are at least as precise and are probably as accurate as they are (AU)