Construction of an Optical Sensor for the Determination of Ascorbic Acid Using Ionic Liquids as Modifier

Abstract

An optode was designed for an indirect determination of ascorbic acid by using neocuproine, which has been coated on transparent triacetylcellulose film as a membrane. The proposed method is based on the oxidation of ascorbic acid to dehydroascorbic acid with the Cu(II) and neocuproine reagent. The increase in the absorbance value of the optode at the maximum wavelength of 455 nm was related to the ascorbic acid concentration in aqueous samples. The sensitivity of the method was improved by using room-temperature ionic liquid, [C₈MIM][PF₆]. The linear dynamic range for the determination of ascorbic acid was 7.4 × 10⁻⁵ – 3.5 × 10⁻³ mol L⁻¹ with a limit of detection of 2.2 × 10⁻⁵ mol L⁻¹ (n = 10) and a response time range of 6.0 – 8.0 min. The optode was successfully applied for the determination of ascorbic acid in orange juice.