Carbon paste electrode modified with pine kernel peroxidase immobilized on pegylated polyurethane nanoparticles

In the present work, a carbon paste electrode based on pine kernel, a seed from Paraná pine (Araucaria angustifolia), for the determination of dopamine in pharmaceutical products was developed. The biodevice was constructed by the immobilization of peroxidase extracted from the pine kernel homogenate on pegylated polyurethane nanoparticles. Square-wave voltammetry (SWV) experiments were performed to investigate the performance of the modified carbon paste electrode. The best analytical response was obtained for a 75:15:10% (w/w/w) composition of graphite powder:mineral oil:polyurethane nanoparticles containing 2.5 units of peroxidase mg−1 of carbon paste, 0.1 mol L−1 phosphate buffer solution (pH 6.5), 2.0 × 10−3 mol L−1 hydrogen peroxide, 80 mV pulse height and 60 Hz frequency. The analytical curve was linear for dopamine concentrations from 9.9 × 10−5 to 1.6 × 10−3 mol L−1 (r = 0.9995) and the regression equation was found to be ΔI = 2.1 + 7.4 × 103 [dopamine] with a limit detection of 9.0 × 10−6 mol L−1. The recovery of dopamine from pharmaceutical samples ranged from 97% to 103% and the results obtained using the proposed modified carbon paste electrode and those obtained by the official method are in agreement at the 95% confidence level.