Effect of silver-modified silica on retention and selectivity in normal-phase liquid chromatography

Abstract

Silica surface modification by silver ions has been studied by high-performance liquid chromatography. After treatment with silver nitrate at pH 4.3 and 7.0, the silver-modified silicas were used in physical and chemical analyses. From measurement with an atomic absorption flame emission spectrophotometer, the amount of silver adsorption was determined to be 420 ppm on silver-modified silica at pH 4.3 and 4500 ppm at pH 7.0. The separation factors, α, of methyl linoleate versus methyl linolenate were measured to be 1.18 on silver-modified silica at pH 7.0, but could not be measured on original non-modified silica, using 1,4-dioxane- n-hexane (2.0:98.0, v/v) as the eluent. The experimental results showed that silver-modified silicas gave significant improvement in the separation of the model unsaturated fatty acids.