Monolithic octadecylsilyl-silica gel column for the high-speed ion chromatographic determination of acidity

Abstract

A monolithic ODS-silica gel column modified by saturating it with lithium dodecylsulfate (Li-DS) was used to demonstrate the high-speed separation of H + from other mono- and divalent cations, such as Na +, NH 4 +, K +, Mg 2+ and Ca 2+ using ion chromatography (IC). Using a 5 m M EDTA-2K solution containing 0.10 m M Li-DS (pH 4.80) as eluent, H + was eluted with a sharp and symmetrical peak within 1.0 min before other cations at a flow-rate of 1.5 ml min −1. The rapid elution of H + and its conductimetric detection could be attributed to the presence of EDTA (HY 2−), which can convert H + ions as anions, i.e. H ++H 2Y 2−→H 3Y −. The acidity of rainwater and deionized water samples was determined using this IC system with satisfactory results.