Amperometric determination of sarcosine with sarcosine oxidase entrapped with Nafion on manganese dioxide-modified screen-printed electrodes

Abstract

A simple biosensor, constructed by bulk-modification of carbon ink with manganese dioxide as an electron mediator and sarcosine oxidase enzyme as a biocomponent entrapped with Nafion was developed and investigated for its ability to serve as amperometric detector of sarcosine in flow injection analysis (FIA) mode. The dependence of the response on the applied potential, the pH of phosphate buffer, the concentration and the flow rate were studied. Factors influecing the amperometric response were studied in detail. The sensors could be operated at optimized conditions which were found as follow: flow rate, 0.2 ml min-1; carrier, 0.1 M phosphate buffer (pH 8.25); injection volume, 150 ul; operation potential, 0.38 V vs. Ag/AgCl. The sensor exhibited a linear increase of amperometric signal with the concentration of sarcosine in the range of 10-250 ppm (R2=0.9992) with a detection limit (evaluated as 3o) of 2.5 mg l-1. The developed biosensors exhibited a good selectivity over other biogenic amines. Its application in food analysis was also examined.