Differential pulse polarographic determination of rhodium(III) and ruthenium(III) in synthetic samples after preconcentration of their quinolin-8-olate complexes onto microcrystalline naphthalene

Rhodium(III) and ruthenium(III) form water-insoluble quinolin-8-olate complexes that are quantitatively retained on microcrystalline naphthalene in the pH ranges 5.1-6.8 and 4.0-6.5, respectively. The metal complex is desorbed with 10 ml of 2 M HCl and determined using a differential pulse polarograph. The detection limits are 0.06 ppm for rhodium and 1.0 ppm for ruthenium. Linearity is maintained in the concentration ranges 0.25-7.50 ppm for rhodium and 2.0-60.0 ppm for ruthenium, with correlation factors of 0.9997 and 0.9994 and relative standard deviations of 0.79 and 0.81%, respectively. The effects of various parameters such as pH, volume of aqueous phase, reagent and naphthalene concentrations, and interference of a large number of metal ions and anions on the determination of these metals were studied in detail to optimize the conditions for their trace determination in various synthetic samples corresponding to real samples. The method is found to be highly selective, fairly sensitive, simple, rapid, and economical and may be safely applied to their determination in different complex materials such as environmental samples and ores. (C) 1998 Academic Press.