Attenuated Total Reflectance Spectra of Colloidal and Particulate Silica Samples in Aqueous Media

Abstract

We have measured and compared ATR/FT-IR spectra of aqueous dispersions of colloidal silica, and aqueous suspensions of particulate silica, over ranges of bulk concentrations using CIRCLE® and Contact Sampler™ cells. Procedures are described for quantitative analyses of each silica type. Detection limits are approximately 0.001% for the particulate species. The spectra of particulates are distorted by refractive-index effects to low frequency of the main analytical bands around 1090 cm-1, but the distortions are proportional to concentration and do not interfere with the precision of analyses. We recommend either ATR cell, but the Contact Sampler™ is more convenient.