Development of a Disposable All-Solid-State Ascorbic Acid Biosensor and Miniaturized Reference Electrode Fabricated on Single Substrate

A low-cost, small-size, and all-solid-state biosensor for the specific determination of L-ascorbic acid was developed. The sensor array was fabricated by screen printing, and the ruthenium oxide (RUO₂) thin film was deposited on the working area of each sensor by an RF sputtering method for surface modification. A conductive polymer (polypyrrole) miniaturized reference electrode was used in combination with the biosensor. The ascorbate oxidase was immobilized with 3-glycidoxypropyltrimethoxysilane (GPTS) methods in the bioactive membrane layer. In accordance with experiment results, the sensor has the better average sensitivity of 51.85 mV/pH between pH 1 and pH 13. The investigated characteristics in the polypyrrole film modified reference electrode show a very small drift voltage (5 mV/h) and the standard deviation of the reference electrode is 1.093 mV. According to the experiment results, the potential response of the enzyme-based biosensor depends linearly on L-ascorbic acid concentration between 0.02 mM and 1 mM with a linear correlation coefficient of 0.86 and the sensitivity is 13.85 mV/mM.