Electrochemical determination of adsorption isotherm of Mordant red 19 on mercury and its analytical application for the indirect determination of uranium

摘要

A voltammetric method for the determination of trace level of uranium is described. The method is based on an adsorptive accumulation of the uranium-Mordant red 19 (MR19, 4-[(5-chloro-2-hydroxy-3-sulfo-phenyl)azo]-5-hydroxy-3-methyl-1-phenyl-pyr azole, sodium salt) complex on a hanging mercury drop electrode followed;ed by the reduction of the adsorbed complex. A detection limit of 8.0 x 10(-11) M uranium can be obtained with a controlled adsorptive accumulation for 10 min. A linear response is obtained from 4.0 x 10(-8) M to 5.0 x 10(-6) M concentration of uranium with the relative standard deviation of 3.9 % at 5.0 x 10(-8) M uranium. The interfacial and redox behavior are characterized by cyclic voltammetry. Chronocoulometry has been used to evaluate the surface coverage us, the concentration of MR19 in 0.05M KHP buffer. The surface excess obeys Langmuir isotherm over the concentration range from 1.0 x 10-(8) M to 1.0 x 10(-6) M with a saturation limit of 1.08 x 10(-10) mol/cm(2) which corresponds to the cross-sectional area of 154 Angstrom(2) /molecule. The effect of various operational parameters on the stripping response is discussed. Also interferences from other metal ions are examined. [References: 24]