Comparison of fluorimetric and inductively coupled plasma mass spectrometry detection systems for the determination of aluminium species in waters by high-performance liquid chromatography

Abstract

The comparison of element-specific detection using HPLC–ICP-MS with an established HPLC–fluorimetric method for aluminium speciation in waters is described. This comparison allowed the identification of some problems with a fluorimetric detection method based around 8-hydroxyquinoline-5-sulfonic acid, particularly its comparatively poor selectivity and Al-species dependent response factors. The power of ICP-MS as a detector for HPLC systems is demonstrated by the simultaneous detection of Al, Mg, Zn, and Fe. The increased selectivity of ICP-MS over molecular fluorescence is shown in the reliable quantification of Al³⁺ and AlF²⁺ in a range of tap and natural water samples. The fluorimetric technique exhibited varying response factors to different aluminium species while the specific detector gave constant signals. Both techniques provided similar values for the ‘free’ Al³⁺ fraction in a variety of natural waters but systematic differences were obtained in the quantification of the AlF²⁺ fraction. Problems with the ICP-MS detection method for Al-speciation analysis such as ion interferences and salt concentration of the mobile phase are commented upon.