Analysis of copper(ii) using the ascorbate/oxygen system – a valuable undergraduate resource
Sean Tobin A , John Cassidy
A * , Kevin Kurian B and Anthony Betts B
A School of Chemical and BioPharmaceutical Sciences, Technological University Dublin, Grangegorman, Dublin D07 ADY7, Ireland.
B FOCAS Institute, Applied Electrochemistry Group, Technological University Dublin, Camden Row, Dublin D08 CKP1, Ireland.
Australian Journal of Chemistry 75(10) 835-838 https://doi.org/10.1071/CH22164
Submitted: 27 July 2022 Accepted: 11 October 2022 Published: 10 November 2022
© 2022 The Author(s) (or their employer(s)). Published by CSIRO Publishing.
Abstract
In deionised water, ascorbic acid (AH−), through oxidation by oxygen in the presence of copper(ii), was found to degrade with zero-order kinetics. The magnitude of the reaction rate varied directly with the copper(ii) concentration. At a higher pH (7.4), the same reaction was found to be pseudo-first order. Once again, the magnitude of the rate increased linearly with copper(ii) concentration at a micromolar level. Dissolved oxygen levels, in excess AH− and trace copper(ii), displayed similar kinetics under both conditions. Monitoring of either AH− levels or dissolved oxygen concentration was found to be a useful novel undergraduate practical laboratory for trace copper(ii) determination. Students can measure the kinetics for standards and their unknown copper solution and quantitate the unknown copper.
Keywords: analysis, ascorbic acid, copper, dissolved oxyget probe, kinetics, UV spectroscopy.
References
[1] T Akbıyık, İ Sönmezoğlu, K Güçlü, I Tor, R Apak, Protection of ascorbic acid from copper(II)−catalyzed oxidative degradation in the presence of fruit acids: citric, oxalic, tartaric, malic, malonic, and fumaric acids. Int J Food Prop 2012, 15, 398.| Protection of ascorbic acid from copper(II)−catalyzed oxidative degradation in the presence of fruit acids: citric, oxalic, tartaric, malic, malonic, and fumaric acids.Crossref | GoogleScholarGoogle Scholar |
[2] WL Boatright, Oxygen dependency of one electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid. Food Chem 2016, 196, 1361.
| Oxygen dependency of one electron reactions generating ascorbate radicals and hydrogen peroxide from ascorbic acid.Crossref | GoogleScholarGoogle Scholar |
[3] E Silverblatt, AL Robinson, CG King, The kinetics of the reaction between ascorbic acid and oxygen in the presence of copper ion. J Am Chem Soc 1943, 65, 137.
| The kinetics of the reaction between ascorbic acid and oxygen in the presence of copper ion.Crossref | GoogleScholarGoogle Scholar |
[4] J Shen, PT Griffiths, SJ Campbell, B Utinger, M Kalberer, SE Paulson, Ascorbate oxidation by iron, copper and reactive oxygen species: review, model development, and derivation of key rate constants. Sci Rep 2021, 11, 7417.
| Ascorbate oxidation by iron, copper and reactive oxygen species: review, model development, and derivation of key rate constants.Crossref | GoogleScholarGoogle Scholar |
[5] N Künzli, IS Mudway, T Götschi, T Shi, FJ Kelly, S Cook, P Burney, B Forsberg, JW Gauderman, ME Hazenkamp, J Heinrich, D Jarvis, D Norbäck, F Payo-Losa, A Poli, J Sunyer, PJA Borm, Comparison of oxidative properties, light absorbance and total and elemental mass concentration of ambient PM2.5 collected at 20 European sites. Environ Health Perspect 2006, 114, 684.
| Comparison of oxidative properties, light absorbance and total and elemental mass concentration of ambient PM2.5 collected at 20 European sites.Crossref | GoogleScholarGoogle Scholar |
[6] W Zeng, F Martinuzzi, A MacGregor, Development and application of a novel UV method for the analysis of ascorbic acid. J Pharm Biomed Anal 2005, 36, 1107.
| Development and application of a novel UV method for the analysis of ascorbic acid.Crossref | GoogleScholarGoogle Scholar |
[7] vanLoon GW, Duffy SJ. Environmental Chemistry, a global perspective. Oxford University Press; 2000. p. 227.
[8] J Xu, RB Jordan, Kinetics and mechanism of the reaction of aqueous copper(II) with ascorbic acid. Inorg Chem 1990, 29, 2933.
| Kinetics and mechanism of the reaction of aqueous copper(II) with ascorbic acid.Crossref | GoogleScholarGoogle Scholar |
[9] P Zhou, J Zhang, Y Zhang, Y Liu, J Liang, B Liu, W Zhang, Generation of hydrogen peroxide and hydroxyl radical resulting from oxygen-dependent oxidation of l-ascorbic acid via copper redox-catalyzed reactions. RSC Adv 2016, 6, 38541.
| Generation of hydrogen peroxide and hydroxyl radical resulting from oxygen-dependent oxidation of l-ascorbic acid via copper redox-catalyzed reactions.Crossref | GoogleScholarGoogle Scholar |
[10] https://www.vernier.com/files/manuals/do-bta/do-bta.pdf [accessed 7 July 2022].
