Amperometric Tyrosinase Based Biosensors for Serotonin Detection

An amperometric biosensor for serotonin detection and quantification, using a carbon paste electrode modified with cobalt(II) phthalocyanine and tyrosinase is described. The tyrosinase immobilization on carbon nanopowder was made using drop-and-dry method followed by cross-linking with glutaraldehyde. The novel biosensor response was optimized using serotonin and it presented the best performance in 0.01 mol L phosphate buffer (pH=7.0). Under optimized working conditions at 0.1 V versus Ag/AgCl, a linear response range from 4 to 140 M was obtained. The detection limit was 0.84 M and the response time was lower than 5 s. The novel biosensor presented a stable response during 100 cycles under continuous monitoring by cyclic voltammetry. The variation of the response between four biosensor preparations was lower than 2%. The biosensor was applied in the determination of serotonin in walnut samples obtaining a good recovery average of 102%.