Electroanalytical study of tricyclic antidepressants
Anodic electroactivity, shown by clomipramine, desipramine, dibenzepin, dothiepin, imipramine, opipramol and trimipramine has been studied at rotating disc electrodes of platinum and gold in sulphuric acid and in buffer media by single scan voltammetry, and at stationary disc electrodes by cyclic voltammetry. Potentiostatic and amperostatic coulometry have been used to determine the number of electrons involved in the reactions. Rapid voltammetric determinations of the active drugs have been evaluated in the best medium, 0.1 mol l–1 sulphuric acid. Adsorption of the oxidation product on the electrodes prevents determination of clomipramine and restricts the concentration range for imipramine and trimipramine. The kinetic parameters, half-wave potentials, mass and charge-transfer rate constants and charge-transfer coefficients have been determined under a wide range of conditions. Electrode reaction mechanisms have been elucidated. Dothiepin is oxidised by a single four-electron step to the sulphone. The azepines are oxidised to a radical that dimerises rapidly before a further one-electron step produces the dimer diradical; opipramol can undergo a further four-electron oxidation of the piperazine ring in the side chain to the 1,4-dihydropyrazine derivative.