Copper (II)-Catalyzed Oxidation of Ascorbic Acid: Ionic Strength Effect and Analytical Use in Aqueous Solution

Abstract

Copper is an important metal both in living organisms and in the industrial activity of humans, it is also a distributed water pollutant and a toxic agent capable of inducing acute and chronic health disorders. There are several fluorescent chemosensors for copper (II) determination in solutions; however, they are often difficult to synthesize and solvent-sensitive, requiring a non-aqueous medium. The present paper improves the known analytical technique for copper (II) ions, where the linear dependence between the ascorbic acid oxidation rate constant and copper (II) concentration is used. The limits of detection and quantification of the copper (II) analysis kinetic method are determined to be 82 nM and 275 nM, respectively. In addition, the selectivity of the chosen indicator reaction is shown: Cu2+ cations can be quantified in the presence of the 5–20 fold excess of Co2+, Ni2+, and Zn2+ ions. The La3+, Ce3+, and UO22+ ions also do not catalyze the ascorbic acid oxidation reaction. The effect of the concentration of the common background electrolytes is studied, the anomalous influence for chloride-containing salts is observed and discussed.

Influences of nitrogen base excess on ARGET ATRP of styrene with ascorbic acid acetonide and traces of oxygen and water

“…To test this and to obtain more information about the system, in a second experiment we explore the copper-catalyzed oxidation of H 2 AAIPI by molecular oxygen, in analogy with what has been reported in the literature. 40 In it, we expect Cl–Cu( ii )TPMA to be reduced by H 2 AAIPI and rapidly re-oxidized by O 2 according to a 4e − /4H + pathway 41 – thus, water is produced until all H 2 AAIPI is consumed. In the resulting catalytic cycle (depicted in simplified form in Fig.…”

“…All spectra were recorded with a model V-570 spectrophotometer (Jasco, Tokyo, Japan). 40 Specifically, solutions of CuCl 2 / TPMA, H 2 AAIPI, KOH, DBU, DIPEA, and TMP were prepared freshly. To carry out the experiment under an inert atmosphere (as reported in Fig.…”

Redox Chemistry of “Neglected Copper‐Tris” Complex in Presence of Ascorbic Acid and O2

“…However, its role in human body is still subjected to further investigation due to its antioxidant, pro-oxidant and chelating effects. [22][23][24][25] It is widely used in medical practices as a metal chelating agent, especially in the case of iron overload. [23] On the other hand, H 2 A is also known to act as a pro-oxidant by the reduction of certain metal ions (Fe/Cu) under certain conditions by commencing a cascade of redox reactions which generates ROS resulting in oxidative modification or damage of biomolecules.…”

“…[17,28] However, Cu could be released from the bound state during impairment of Cu-trafficking or tissue injury, or copper-overload diseases [17] and might subsequently interact with H 2 A which might invoke complicated redox reactions. [25,26] Even in amyloid peptide, HisÀ Cu II À His (having low redox potential) is reduced by H 2 A and produces ROS under oxidative stress. [16,29] Based on the cytotoxic property of H 2 A with copper/iron, it is also used as a catalytic therapy in cancer treatment.…”

“…H 2 A is an important human diet, and a well‐known natural compound that plays multiple roles in human. However, its role in human body is still subjected to further investigation due to its antioxidant, pro‐oxidant and chelating effects [22–25] . It is widely used in medical practices as a metal chelating agent, especially in the case of iron overload [23] .…”