Aluminium fractioning with cation exchanger

The method aims to estimate the content of reactive aluminium, which comprises the forms of aluminium considered to be the most toxic. In most natural waters, these forms constitute relatively weak complexes between Al³⁺ and various ligands. The complexes disintegrate relatively easy into free Al³⁺ ions.

The analysis is performed by dividing untreated water in two fractions prior to quantification:

1. "Al_ICPKJB", which has passed through a cation exchanger, where the reactive component of the aluminium attaches to the cation exchanger. The remainder thus consists of the non-reactive aluminium. It should be pointed out that this fraction, where "KJB" stands for "cation-exchangeable", actually is the complete opposite, i.e. the non-cation-exchangeable.
2. "Al_NI", which is measured from water that has not passed through the cation exchanger, and thus constitutes the total content. A smaller difference may be experienced compared to the total content measured from an acidified sample, as there is no desorption from e.g. larger particles, and because there might be some adsorption to the duct walls.

Both fractions are analysed immediately after fractionation with ICP-OES. The proportion of unstable aluminium is determined as the difference between Al_NI and Al_ICPKJB.

Known issues with the parameter and/or important method changes

No problems reported.

Current method of measurement

The method was cancelled by the end of 2017. 

Previous methods

2000 01 –  2017 12
Fractionation method: Laboratory specific method, Aluminium fractionation 2006-06-01.
Analysis method: ICP (Inductively coupled plasma), SS-EN ISO 11885:2009.
Instrument: VarianVista AX