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Optimization of conditions for voltametric determination of tryptophan in pharmaceutical formulations using overoxidized polypyrrole glassy carbon electrode

A.Shokuhi Rad, M.Ardjmand

Trp was preferentially concentrated to the electrode under an open circuit condition, and was determined by the cyclic voltammetric technique .The electrocatalytic ability of the modified surface of the electrode allows the possibility of applyingmoderate potential and current for the voltammetric detection of Trp. The electrocatalytic behavior of Trp is elucidated with respect to solution pH, operating potential and other variables as well as the chemicallymodified electrode(CME) preparation conditions.Optimized conditions allowed the determination of Trp with detection limit of 6.9M in liner dynamic rang 25 to 225M (n=7, R2=0.9992 ) at overoxidaized polypyrrole/GC electrod. The optimized condition was obtained via two consective stages: (a) electrochemical stage where two cycles of cyclic voltametrywere applies at 0.30 to 0.85Vrange and the scan rate of 200mV/ s and (b) overoxidation stage where the electrode was placed in 0.50M NaOH solution and 7 cycles were applied at 0.30 to 1.10V range and the scan rate of 20mV/s.