An electrocatalytic based sensor fabricated for square wave voltammetric determination of methyldopa in the
presence of tyrosine. For this goal, carbon paste electrode modified with NiO nanoparticle (NiO/NPs) and 2-
(3,4-dihydroxyphenethyl)isoindoline-1,3-dione (DHPID) (CPE/DHPID/NiO/NPs) suggested as a highly selective
sensor. The CPE/DHPID/NiO/NPs showed an excellent character for electrocatalytic oxidization of methyldopa
in aqueous solution. For the mixture containing methyldopa and tyrosine, the oxidation peaks potential well separated from each other with differential potential ~500 mV. Methyldopa peak current increased linearly with its
concentration at the ranges of 0.08–500 μM. The CPE/DHPID/NiO/NPs was successfully used for the analysis of
methyldopa in drug samples.