DIRECT DETERMINATION OF INORGANIC-IONS AT SUB-PPB LEVELS BY ION CHROMATOGRAPHY USING WATER AS A MOBILE-PHASE

Electrostatic ion chromatography (EIC) was used for determination of t race level inorganic ions. EIC is a new method of separating ions base d on simultaneous electrostatic attraction and repulsion interactions between analyte ions and fixed positive/negative charges of a stationa ry phase, having the special advantage of using only water as the mobi le phase. Initial results showing two elutions of the same analyte gav e new insights into the mechanism of EIC. It suggests that the zwitter ionic stationary phase, like a single charged stationary phase, has a Stern layer and a diffuse layer. The first elution is from the diffuse layer, and the second is from the Stern layer. As simpler analysis is facilitated by a single elution, a new species of inorganic salt with a longer elution time was added to the original sample solution in or der to release analyte ions from the Stem layer to the diffuse layer. The newly introduced salt is called a sacrifice species. Without preco ncentration, inorganic ions at sub-ppb levels were successfully detect ed by this method.