Progress in Silica Chemistry - Determination of Physico-Chemical Parameters via Near-Infrared Diffuse Reflection Spectroscopy

Abstract

In analytical chemistry, silica gel plays a pre-dominant role in separation science. It is the most important sta- tionary phase in chromatography and electrophoresis. Separation efficiency is directly dependent on the quality and physical properties of the chromatographic bed. Therefore, methods for the physicochemical characterisation of silica sta- tionary phases have been developed over the past decades to fulfil the necessity of pattern control: Brunnauer Emmet Teller (BET) for determination of surface area, mercury intrusion porosimetry (MIP) and size exclusion chromatography (SEC) for pore-size measurement and light-scattering (LS) to evaluate the particle size. Beside that these methods are elaborate and time-consuming and the use of MIP is awkward due to the necessity to ply with poisonous mercury. Therefore, we introduce near-infrared reflection spectroscopy (NIRS) in the fibre-optics mode for a fast (few seconds), easy to handle and highly reproducible new analytical technique to characterise surface area, particle size inm- and po- rosity in lower nm- range. This new analytical NIRS tool is suitable for high sample throughput and therefore aims at high interests in the nano-field. Determination of particle size, porosity and surface area are achieved with a linear correlation coefficient R 2 > 0.98, BIAS < 1.26 � 10 -14 . Beside these advantages, our introduced NIRS approach allows physicochemi-