Kinetic-spectrofluorimetric determination of trace amounts of iridium

A simple and sensitive kinetic-spectrofluorimetric method is described for the determination of iridium(IV) and the possible mechanism of catalytic reaction is proposed. The method is based on the fluorescent quenching reaction of salicylaldehyde p-nitro-benzoylhydrazone (SAP-NBH) with potassium periodate, inhibited by Ir(IV) in a water–ethanol (7.3+2.7, v/v) medium at pH 10.70 and 55 °C. Cetyltrimethyl ammonium bromide sensitized the determination obviously. SAP-NBH was newly synthesized and its ionization constants were established spectrophotometrically. The reaction was monitored by measuring the change rate of fluorescence (λ ex/em=252/310 nm) after a fixed time of 5 min. The proposed method allowed the determination of iridium in the range of 0.11–18 ng ml−1 with a RSD of 2.5% at a concentration of 10 ng ml−1 and the detection limit was down to 0.09 ng ml–1. The method was found to be relatively selective and was applied successfully to determine iridium in synthetic mixtures and mineral sample with the results consistent well with the ref. values.