Biosensors based on bean sprout homogenate immobilized in chitosan microspheres and silica for determination of chlorogenic acid

Biosensors for the square wave voltammetric determination of chlorogenic acid were developed by immobilization of a homogenate of fresh bean sprouts ( Vigna radiata) in chitosan microspheres (biosensor I) and silica (biosensor II) crosslinked with glutaraldehyde and epichlorohydrin. The bean sprout tissue acts as a source of peroxidase which, in the presence of hydrogen peroxide, catalyzes the oxidation of chlorogenic acid. The electrochemical reduction of this product was obtained at a potential of +0.18 V (biosensor I) and at a potential of +0.22 V (biosensor II). The chlorogenic acid concentration was linear in the range of 4.89 × 10 −6 to 3.20 × 10 −4 M (biosensor I) and 4.89 × 10 −6 to 4.85 × 10 −5 M (biosensor II) with detection limits of 8.02 × 10 −7 and 8.52 × 10 −7 M, respectively. These biosensors demonstrated long-term stability (4 months; 300 determinations) and reproducibility, with a relative standard deviation of 3.5% (biosensor I) and 1.5% (biosensor II). The recovery of chlorogenic acid from four coffee samples ranged from 96.5 to 102.6% (biosensor I) and 91.3 to 115.5% (biosensor II). Results obtained for the determination of chlorogenic acid in these samples using the proposed biosensors and those obtained using the capillary electrophoresis method are in agreement at the 95% confidence level.