Application of polyethylene glycol for "electrochemical masking" in direct-current polarography.

The use of polyethylene glycols (PEG) of molecular weight from 200 to 15,000 for electrochemical masking has been investigated. A pH-4.4 tartrate buffer was found to be the most suitable supporting electrolyte, and 0.1% the optimum PEG concentration. PEGs of m.w. below 600 had little effect on the waves examined, and are useless for electrochemical masking. Under the conditions chosen, the waves of Bi(III), Sb(III) and In(III) are completely suppressed; the Cd(II) and Pb(II) waves are shifted to more negative potentials, and the Tl(I) wave is scarcely affected by PEGs. The Cu(II) wave behaves differently from the others. A method is proposed for the determination of lead and/or thallium in the presence of up to 5000-fold w/w ratios of bismuth, antimony or indium. The determination of both lead and thallium is only possible when the amounts are not too different, as the waves are quite close. Copper(II) interferes.