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 degrees 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 (lambda 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.