Tyrosine acts as precursor for the biosynthesis of melanin via L-dopa. The darkening of potato tuber during physical injury was due to the conversion of tyrosine to melanin. The present work reports the simultaneous determination of L-dopa and tyrosine present in the aqueous extract of potato tuber through differential pulse voltammetric (DPV) technique using gold modified pencil graphite electrode (GPGE). It was found that tyrosine and L-dopa could be catalytically oxidized with diffusion-controlled characteristics at this electrode, which could be applied for the estimation of L-dopa present in biological samples. Oxidation peak potentials observed for L-dopa and tyrosine were at 204 mV and 659 mV respectively. The similar oxidation peak potentials were observed for the aqueous extract of potato tuber. The results demonstrated that the GPGE exhibited high electro-catalytic activity, high sensitivity and possess good analytical performance towards the simultaneous determination of L-dopa and tyrosine from potato tuber extract.
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