Portable fractionation device and screen-printed electrode for measurement of reactive aluminium in environmental samples

Rapidly reacting aluminium species (the 'reactive' fraction, Al3++Al(OH)(2+)+Al(OH)(2)(+))may be toxic in the environment. As aluminium speciation can change with sample storage, on-site determination of reactive aluminium is expected to give the most meaningful data. We describe here aluminium fractionation and measurement methods which can be easily adapted for use in the field. Fractionation of the aqueous sample utilises a hand-operated syringe to pass the sample and eluent over a microcolumn of oxine (8-quinolinol)-derivatised Fractogel. Aluminium eluted from the column is determined voltammetrically at an alizarin-modified graphite screen printed electrode. Using synthetic ligand-aluminium solutions, the method is demonstrated to selectively target rapidly reacting aluminium. Potential interfering metal ions are removed by the microcolumn retention/elution protocols. The linear working range for the alizarin-modified electrodes is 0.7-18 mu M Al. Four replicate fractionation/analysis measurements of a 5 mu M Al standard gave a relative standard deviation (RSD) of 11.6% for the combined method. Determination of reactive aluminium in soil solutions gave results which agree with those obtained using an established flow method with spectrophotometric detection. (C) 1999 Elsevier Science B.V. All rights reserved.