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

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+, NH4+, K+, Mg2+ and Ca2+ using ion chromatography (IC). Using a 5 mM EDTA-2K solution containing 0.10 mM 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 (HY2−), which can convert H+ ions as anions, i.e. H++H2Y2−→H3Y−. The acidity of rainwater and deionized water samples was determined using this IC system with satisfactory results.