Scheme 1. Proposed Pathway for the Electrochemical Precipitation and Strippinga.
aThe left panel shows the heterogeneous reactions causing a local pH change at the electrode surface in a bulk solution of 10 mM cocaine. The high pH deprotonates the cocaine salt to locally form the cocaine base, which precipitates onto the electrode surface. The right panel shows the oxidation of the cocaine precipitate in a solution of salt water (0.5 M KCl).