Polarographic determination of In(III) and Cd(II) in the presence of a crown ether

Summary The simultaneous determination of In(III) and Cd(II), whose reduction potentials are very close to each other, was investigated by polarography in the presence of a crown ether such as 12-Crown-4, 15-Crown-5, or 18-Crown-6. An addition of the crown ether shifts the reduction potential of In(III) towards the negative side, its current remaining unchanged, while that of Cd(II) almost did not change, also leaving the wave current constant. Therefore, the difference in reduction potentials between two ions became appreciably large for the simultaneous determination by polarography.