Ascorbic Acid Determination Based on Electrocatalytic Behavior of Metal-Organic Framework MIL-101-(Cr) at Modified...

Background: Metal-organic frameworks (MOFs) are classified as microporous materials. They have large surface areas, low framework densities, accessible cages, and tunnels with modifiable pores. Objective: The MOF MIL-101(Cr) with a large pore volume was synthesized hydrothermally and used in the electrochemical reactions as an electrocatalyst for the determination of ascorbic acid (AA). The synthesized MOF was characterized by scanning electron microscopy and X-ray powder diffraction. Methods: The electrocatalytic behavior of a carbon-paste electrode modified with MIL-101(Cr) was studied through electro-oxidation of AA by cyclic voltammetry and square wave voltammetry. The conventional three-electrode cell system, consisting of Ag/AgCl (3 M KCl) as the reference, platinum wire as the counter electrode, and modified carbon paste as the working electrode, was used in the experiment. Results: Under optimized experimental conditions, the electrode revealed a linear relationship between the oxidation peak current and concentration of AA over a wide range from 0.01 to 10 mM with the LOD of 0.006 mM (3 Sb/m). The results showed that 100-fold of Na⁺, K⁺, Mg²+, Ca²⁺, Cl^-, SO₄^2-, sorbitol, sucrose, fructose, citric acid, 40-fold of NO₃-, glucose, sucrose, urea, and 10-fold of uric acid had no significant interference. The method was adapted for the determination of the concentration of AA present in two real samples (vitamin C tablet and vitamin C effervescent tablet) with recovery of 97.0 and 96.0%, respectively. Conclusions: A simple, sensitive and reliable modified electrode has been established and applied for the determination of AA. Highlights: The modified electrode represented a good performance in the analysis of the real sample.