MODIFICATION OF ELECTRODES WITH ADSORBED POLYAMINO ACIDS .2. ADSORPTIVE STRIPPING VOLTAMMETRIC DETERMINATION OF HEXACYANOFERRATE(III) AT A HANGING MERCURY DROP ELECTRODE IN THE PRESENCE OF AN ADSORBED LAYER OF COPPER-MODIFIED POLY-L-LYSINE

Hexacyanoferrate(III) was determined at the 2 x 10(-8)-1.75 x 10(-7) M level by differential-pulse cathodic stripping voltammetry after accumulation for 2 min at a hanging mercury drop electrode in the presence of a poly-L-lysine film modified with copper(II). Measurements were made by using the reduction peak at-0.45 V, which was observed in acid or neutral solution in the presence of both copper(II) and hexacyanoferrate(III). The effects of pH, accumulation potential, accumulation time and the presence of interferents were also investigated. Zinc is a serious interferent owing to the formation of insoluble compounds, and surfactants inhibit the accumulation of hexacyanoferrate(III).