A novel pequi fruit (Caryocar brasiliense Camb) homogenate source of polyphenol oxidase was obtained and immobilized in chitosan crosslinked with cyanuric chloride (CHcych-PPO) A biosensor was developed and used for the square-wave voltammetric determination of thiodicarb Several parameters were investigated to evaluate the performance of this biosensor in the presence of hydroquinone and thiodicarb The best response was obtained using 70.20 10% (w/w/w) of graphite powder Nujol CHcych-PPO. 250 U mL(-1) of PPO and phosphate buffet solution (0 1 M. pH 7 0) with frequency, pulse amplitude and scan inclement of 10 Hz. 150 mV. and 15 mV, respectively Under optimized operational conditions the thiodicarb concentration was linear in the range of 3 75 x 10(-7) to 2 23 x 10(-6) M with a detection limit of 1 58 x 10(-7) M The biosensor was applied in the determination of thiodicarb in fresh fruit and vegetable samples and the results compared with those obtained using high-performance liquid chromatography (C) 2010 Elsevier Inc All rights reserved