Inorganic-Organic Composite Matrix for the Enzymatic Detection of Phosphate in Food Samples

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In this work, enzymatic determination of phosphate using pyruvate oxidase in food samples is demonstrated using pyruvate oxidase immobilized on a gold substrate functionalized with Cu nanoparticles stabilized on a self assembled monolayer (SAM) of p-mercapto benzoic acid (MBA). Cu nanoparticles stabilized using MBA SAM (Cu/MBA/Au) provides an ideal platform for the nanomolar detection of hydrogen peroxide based on its catalytic electrochemical reduction at the Cu/MBA/Au electrode. This method overcomes the disadvantages due to enzymatic sensing of phosphate based on hydrogen peroxide oxidation, viz., large overpotentials, interferences from easily oxidisable molecules, and sluggish electrochemical oxidation. This method is also simpler compared to other multi enzyme based detection of phosphate as the modification of the electrode with multi enzymes in spatially segregated layers for effective bioelectrocatalysis is quite challenging. Also our method is validated for phosphate detection in beverages. The linear dynamic range of detection is between 40 μM and 350 μM. The sensitivity of detection is 0.006 μA/μM.