Simultaneous determination of metals in two-component mixtures with 5-sulfo-8-quinolinol by using phase-resolved fluorimetry

Determinations of metals in two-component mixtures are described in which 5-sulfo-8-quinolinol is used to produce fluorescent chelates of the metals. The metal chelates have broad, overlapping fluorescence spectra but the fluorescence lifetimes (τ) of the chelates are sufficiently different to permit phase-resolved fluorimetric determinations in which the fluorescence contributions of the two chelates can be resolved. Average determination errors ranged from ?4.1% to 2.1% for each metal chelate in mixtures of zinc and cadmium (Δτ = 1.0 ns), gallium and indium (Δτ = 1.7 ns) and aluminum and gallium (Δτ = 5.3 ns). Limits of detection and determination for each individual metal chelate were found to be three times and five times greater, respectively, for the phase-resolved measurements relative to steady-state measurements under the same experimental conditions. Effects of pH on the fluorescence lifetimes and intesities of the metal chelates were studied.