please see my ppts

absence of a peak does not mean the reaction has not occurred

You can perform the voltammograms without KCl (some redox processes are inhibited by KCl). Also, the pH of the working solution is very important, so you should perform the voltammogram of scopolamine in buffer solutions with different pH (e.g. pH=2; 4; 6.....). There are also  different parameters that may influence the charge transfer, such as: the  scan range of the potential, the scan rate (too slow or too higher),, the concentration of scopolamine (if is too lower you should try a more sensitive technique, i.e. differential pulse voltammetry, square wave voltammetry or others related), the ionic strenght of the buffer solution (try to increase it). Sometimes helps the presence of specific surfactants (anionic or cathionic) in the solution subjected to measurements in order to avoid the fouling of the surface of the working electrode due to the adsorption of product of reactant). Also, some electrochemical preatreatment (electrochemical oxidation of working electrode in different solutions) may enhance the electrode response. The modification of the working electrode surface with compounds containing copper (cupper phthalocyanine) may be another solution for you problem, knowing the affinity of copper toward N atoms.