Automated Dialysis as a Sample Preparation Tool in Ion Chromatography

Ion chromatography (IC) as an analytical technique has seen an impressive surge in popularity. As for samples in a homogenous ionic form,

hardly any preparation steps are required at all. Now, Metrohm’s ( Switzerland) patented stopped-flow dialysis paves the way for the

convenient analysis of demanding samples carrying high organic loads too. In complex matrices carrying high organic loads such as

wastewater, soil eluates or dairy products, extensive sample preparation is mandatory to prevent destruction of the column. Traditional

preparation techniques such as the Carrez precipitation do not provide a satisfying answer as they cannot be automated and are error-prone.

Metrohm’s compact stopped-flow dialysis is an elegant alternative. This fully automated sample preparation setup is based on the selective

diffusion of ions from one liquid (sample/donor solution) to another (acceptor solution) through a membrane. Contrary to dynamic dialysis,

where two solutions continuously pass through the dialysis module, the acceptor solution is stopped until its concentration is the same as that

in the donor solution. This patented stopped-flow procedure takes between 10 and 14 minutes and can be directly coupled to an IC setup.

As the dialysis is performed during the recording of the previous sample’s chromatogram, the overall analysis time is not significantly prolonged.