Determination of metal ion mixtures using pH gradient flow-injection analysis with fluorescence detection

A pH gradient flow-injection system has been combined with fluorescence detection to determine the concentrations of zinc, cadmium, lead, magnesium and aluminium in ternary and quaternary mixtures. A partial least squares algorithm was employed to analyse the fluorescence-time scans produced from mixtures of metal cations, and compared with a classical least squares algorithm. The performance of the partial least squares algorithm was better than the classical least squares approach particularly in more complex mixtures. The method was also used in the analysis of tap water for zinc, aluminium and magnesium and found to be comparable with the results obtained using flame atomic absorption spectrometry.