Low-Temperature Phosphorimetric Determination of Traces of Palladium(II) with Water-Soluble Coproporphyrin III

Abstract

Abstract The characteristics of coproporphyrin III (Copro III) as a chelating agent, a chromogenic agent, and a luminescence agent for metal ions were studied. Copro III forms 1 : 1 complexes with Co(II), Cu(II), Mn(II), Ni(II), Pd(II), and Zn(II). Copper, palladium, and zinc complexes exhibit phosphorescence at liquid nitrogen temperature (77 K), and the intensity of the palladium complex (λPdmax = 659 nm) is 10 and 13 times larger than that of the copper and zinc complexes (λCumax = 685 nm, λZnmax = 702 nm), respectively. Based on these facts, a low-temperature phosphorimetric determination of the 10−8 mol dm−3 level of palladium was developed. The detection limit (S/N = 3 using a 150 W xenon arc lamp as a light source) was 8 × 10−9 mol dm−3, and the relative standard deviation was 2.8% for 6 × 10−7 mol dm−3 Pd(II) (7 determinations). Interference from many metal ions was avoided by selective extraction of palladium(II) as an ion-pair of the bromo complex with H2SO4-tetrabutylammonium bromide-methyl isobutyl ketone systems, followed by back extraction with acetate buffer solution (pH 5.0).