Flow-injection—diode-array detection: a hybrid approach to the automation of simultaneous determinations of metal ions with chromogenic reagents

A straightforward procedure for the simultaneous determination of binary mixtures by using a diode-array detector in a flow-injection manifold and a common photometric reagent for both species is proposed. The optimum conditions are discussed. The high speed at which the detector used can perform spectral scans allows at least one spectrum to be obtained at the maximum of the flow-injection peak. The system was tested for the determination of nickel and zinc with 1-(2-pyridylazo)-2-naphthol (PAN). The coloured complexes formed yield extensively overlapped spectra that can only be resolved through their second derivatives. The proposed procedure allows the determination of these metal ions at the μg ml−1 level, with an r.s.d. of about 4% at a rate of 30–35 samples h−1.