Rapid determination of ascorbic acid, dehydroascorbic acid, and total vitamin C by electrochemiluminescence with a thin-layer electrochemical cell

Abstract

This paper reports on a rapid and sensitive method for the simultaneous determination ascorbic acid (H 2 A), dehydroascorbic acid (DHA) and total vitamin C by electrochemiluminescnece (ECL) using a thin-layer electrochemical cell. Significant ECL signals can be generated by the anodic oxidation of Ru(bpy) 3 2+ in presence of H 2 A or DHA in pH 8.8phosphate buffer solution. Because of the extremely small dead volume of the thin-layer cell (ca.1.5 μL), almost amount of H 2 A is assumed to be completely oxidized to DHA with a short preelectrolysis step. As a result, it is possible to determine the reductive vitamin C (H 2 A) by square wave voltammetry before the pre-electrolysis step, while total vitamin C (sum of H 2 A and DHA) is able to be determined at a subsequent ECL step. The method was employed for the determination of vitamin C in commercial beverages with the analytical results in good agreement with the certified values.

Characterization of electrochemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with glyphosate as coreactant in aqueous solution

“…Because it does not need an excitation light source like fluorometry, ECL provides the advantages of simple instrumentation and low background signal, and the technique has been received considerably attention in the field of analytical chemistry [9][10][11]. ECL reaction from Tris(2,2'-bipyridyl)ruthenium(II), Ru(bpy) 3 2+ can emit light at room temperature in both aqueous and non-aqueous solutions with relatively higher ECL efficiency.…”

Electrochemiluminescence of Tris(2,2′-bipyridyl)ruthenium(II) with Ascorbic Acid and Dehydroascorbic Acid in Aqueous and Non-aqueous Solutions

“…[7][8][9] It will be oxidized to ascorbyl radical anion (A • -), an intermediate in weak basic conditions, and then to dehydroascorbic acid (DHA, oxidized form of vitamin C) via a two-electron and one-proton oxidation process. [10][11][12] Figure 1 shows the chemical structures of H2A, its monoanion (HA -) and its possible oxidative products. In recent years, vitamin C has been studied as a coreactant in Ru(bpy)3 2+ ECL systems.…”

“…Controlled potential and ECL measurements were performed as described. [10][11][12] Emission from the electrode surface was measured with a photomultiplier tube (H7732-10, Hamamatsu Photonics, Shizuoka, Japan) placed opposite the working electrode. ECL spectra were measured with a spectro fluorophotometer (USB2000, Ocean Optics, FL, USA) in continuous potential step mode.…”

“…[10][11][12] However, no experimental evidence was provided in order to produce the stable A • -species at electrode surface, the electrochemical reduction of DHA in MeCN was performed. Figure 3 shows the ECL profile for 0.50 mM Ru(bpy)3 2+ using H2A and DHA as coreactants in MeCN obtained by double pulse potential step measurement.…”

“…where -ΔG (= nFΔE ) is Gibbs energy and TΔS is the temperature-entropy approximation term at 25 C. Because the reaction is in a condensed system, -ΔG ≈ ΔE (in electronvolts, eV), and TΔS for such reactions is typically about 0.1 eV, 12 Eq. (8) can be written as…”