The utilization of the capsaicin modified carbon nanotube modified basal-plane pyrolytic graphite electrode or p-chloranil modified carbon paste electrodes are presented for the determination of pharmaceutical compounds containing amine functionality, such as benzocaine and lidocaine. In detection of benzocaine at a capsaicin modified electrode, the guaiacol functional group is irreversibly electrochemically oxidized to form the o-quinone derivative which then undergoes nucleophilic attack by the aromatic amine group in benzocaine via a 1,4-Michael addition mechanism forming a catechol-amine adduct. The electrochemically initiated formation of the capsaicin-benzocaine adduct causes a linear decrease in the voltammetric signal corresponding to capsaicin which correlates to the added concentration of benzocaine. The applicability of p-chloranil modified carbon paste electrode was also examined with the additions of benzocaine and lidocaine which resulted in a decrease in the voltammetric signals of p-chloranil, which is again due to the formation of an adduct via a similar mechanism to that described above. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.
