Biosensor based on pequi polyphenol oxidase immobilized on chitosan crosslinked with cyanuric chloride for thiodicarb determination

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 buffer solution (0.1 M; pH 7.0) with frequency, pulse amplitude and scan increment of 10 Hz, 150 mV, and 15 mV, respectively. Under optimized operational conditions the thiodicarb concentration was linear in the range of 3.75 × 10−7 to 2.23 × 10−6 M with a detection limit of 1.58 × 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.