A formaldehyde biosensor based on potentiometric ph transducer and immobilised enzyme alcohol oxidase

A potentiometric biosensor for the determination of formaldehyde was developed based on the use of a pH transducer made from methacrylic-acrylic polymer membrane and the enzyme alcohol oxidase (AOX). The biosensor was designed based on the enzymic oxidation of formaldehyde by AOX immobilized in poly(2-hydroxylethyl methacrylate) (pHEMA) hydrogel that was deposited on the pH transducer. A further layer of sol-gel was deposited on top of the pHEMA hydrogel to prevent leaching of AOX and detachment of pHEMA membrane from the pH tranducer. The biosensor gave a linear dynamic response to formaldehyde concentrations from 1-100 mM (R2 = 0.99) with a sensitivity of 43.9 mV/decade. The sensitivity increased to near theoretical value (Nernstian slope) of 52.40 mV/decade when the formaldehye concentrations were 1-10 mM