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AutoNeutralization

The Thermo Scientific™ Dionex™ AutoNeutralization™ system performs an inline neutralization step on a concentrated acid or base before analysis in two dimensional (2-D) ion chromatography. This replaces cumbersome manual dilution and neutralization procedures which would otherwise be required. While dilution can work to reduce the concentration of the interfering matrix ions to a level that does not affect separation, it also reduces the concentration of target ions and consequently compromises detection. Dionex AutoNeutralization solves the analytical problem of achieving trace detection of ions in concentrated acids or bases by neutralizing the sample using an electrolytically regenerated, membrane based neutralizer device. An example of an anion analysis in base is shown here.

After neutralization the sample anions are in solution in water of low ionic strength and can be focused onto a concentrator column. In the Dionex AutoNeutralization process, the concentrated base sample is loaded into the 25 µl sample loop of the sample valve as shown in the figure below.

The sample loop is switched inline with the concentrator column and flushed with a stream of deionized water. This loading water transfers the concentrated base from the sample loop through the Thermo Scientific Dionex ASRN™, where the sample is partially neutralized, then transferred to the 5 ml loop. The recycle valve is then actuated to re-direct the sample through the Dionex ASRN™ for a second time to complete the neutralization. The figure below shows the results of an anion analysis of a concentrated base sample with and without neutralization. As shown  in chromatogram A, the untreated sample shows a significant negative dip in the baseline due to the concentrated base. This matrix interference results in poor chromatography and detection of target anions is virtually impossible. Conversely, chromatogram B shows the results after using the Dionex AutoNeutralization system. Note that the large negative dip is completely eliminated and distinct anion peaks can be readily measured.