Current-sampled polarographic techniques for the measurement of species reduced at more negative potentials than the major component

With conventional d.c. polarography. a particular depolarizer cannot be determined accurately in the presence of a considerable concentration of another species which is reduced at more positive potentials. Current-sampled read-out has been suggested previously to improve the situation; this idea has now been tested experimentally. The read-out of Tast (current-sampled), derivative Tast and pulse polarographic techniques permits determinations of this type to be achieved accurately and conveniently over quite a wide concentration range, provided that a three-electrode potentiostat is used to minimize ohmic iR drop effects. The maximal concentration and the limiting concentration ratio of the two depolarizers were generally fixed more by instrumental than chemical limitations, although at very high concentrations of the major species some evidence of electrochemical interference was found.