Jack Fruit‐Capric Acid Biosensor for Total Phenols Determination in Wastewaters

Abstract

A biosensor based on capric acid/graphite modified with crude extract of jack fruit (Artocarpus integrifolia L.) as the source of polyphenol oxidase (PPO) was developed for determining total phenols in wastewater samples using differential pulse voltammetry (DPV). This enzyme catalyzes the oxidation of phenols to o‐quinones in presence of oxygen and the electrochemical reduction of the product was obtained at a fixed potential of +0.18 V vs. Ag/AgCl (3.0 mol L⁻¹ KCl). The novelty of this biosensor was the application of fatty acids (capric (C₁₀), lauric (C₁₂), miristic (C₁₄), palmitic (C₁₆), stearic (C₁₈), and oleic (C₁₈) acids) as agglutinating agents. Capric acid was found to be the best agglutinating agent. A rectilinear analytical curve for catechol concentration from 5.25 × 10⁻⁶ to 7.80 × 10⁻⁴ mol L⁻¹ (r = 0.9982) with a detection limit of 2.00 × 10⁻⁷ mol L⁻¹ and the recovery of catechol from the sample ranging from 98% to 104% were obtained. The relative standard deviation was <3.0% for a solution of 2.50 × 10⁻³ mol L⁻¹ catechol in 0.1 mol L⁻¹ phosphate buffer solution, pH 7.0 (n = 10) and the results obtained for catechol in wastewater samples using the proposed DPV procedure are in agreement with those obtained using the APHA official methodology. The lifetime of this biosensor was 6 months (at least 300 determinations).

Keywords:

• Crude extract
• Jack fruit
• Total phenols
• Biosensor

Acknowledgments

Financial support from FAPESP and scholarship granted by FAPESP to K.O.L., UFSCar and UFSC are gratefully acknowledged.