Fabrication of a novel palladium membrane sensor for its determination in environmental and biological samples

A novel sensitive, specific, and reversible optical sensor for the palladium(ii) ion was created by impregnating an agarose membrane with 4-(2-amino-3-hydroxypyridine-4-ylazo)1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one (AHDDO). Spectrophotometric studies of complex formation between the AHDDO base ligand and Mn2+, Cd2+, Co2+ Hg2+, Zn2+, Cu2+, Pd2+, Sr2+, Al3+, Fe3+, Au3+, and Ag+ metal ions in an ethanolic solution indicated a substantially larger stability for the palladium ion complex. Therefore, the AHDDO was immobilized on a clear agarose film and used as a suitable ionophore for building a selective Pd2+ optical sensor. By combining the sensing membrane with Pd2+ ions at pH 5.75, a transparent color change from orange to violet was observed. On the immobilization of AHDDO, the effects of ionophore concentration, pH, temperature, stirring, and reaction time were investigated. A linear relationship was observed between the membrane absorbance at 633 nm and Pd2+ concentrations in a range from 15 to 225 ng mL-1 with detection (3 sigma) and quantification (10 sigma) limits of 4.25 and 14.25 ng mL-1, respectively. For the determination of Pd2+ ions, no significant interference from at least 400-fold excess concentrations of a number of possibly interfering ions was found. The sensor exhibits remarkable selectivity for Pd2+ ions and can be regenerated through exposure to 0.15 M HNO3. The sensor has been successfully used to find palladium in biological, soil, road, and water samples. A novel sensitive, specific, and reversible optical sensor for the palladium(ii) ion was created by impregnating an agarose membrane with 4-(2-amino-3-hydroxypyridine-4-ylazo)1,5-dimethyl-2-phenyl-1,2-dihydropyrazol-3-one (AHDDO).