title: Measurement of labile copper in wine by medium exchange stripping potentiometry utilising screen printed carbon electrodes.
abstract: The presence of copper in wine is known to impact the reductive, oxidative and colloidal stability of wine, and techniques enabling measurement of different forms of copper in wine are of particular interest in understanding these spoilage processes. Electrochemical stripping techniques developed to date require significant pretreatment of wine, potentially disturbing the copper binding equilibria. A thin mercury film on a screen printed carbon electrode was utilised in a flow system for the direct analysis of labile copper in red and white wine by constant current stripping potentiometry with medium exchange. Under the optimised conditions, including an enrichment time of 500s and constant current of 1.0μA, the response range was linear from 0.015 to 0.200mg/L. The analysis of 52 red and white wines showed that this technique generally provided lower labile copper concentrations than reported for batch measurement by related techniques. Studies in a model system and in finished wines showed that the copper sulfide was not measured as labile copper, and that loss of hydrogen sulfide via volatilisation induced an increase in labile copper within the model wine system.
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia. Electronic address: aclark@csu.edu.au.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Clark
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Kontoudakis
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.
authors.forename: Celia
authors.initials: C
authors.lastname: Barril
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.
authors.forename: Leigh M
authors.initials: LM
authors.lastname: Schmidtke
authors.affiliation: National Wine and Grape Industry Centre, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia; School of Chemistry, The University of Melbourne, Parkville, Vic. 3010, Australia.
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Scollary
mesh_terms: D002244:Carbon; D003300:Copper; D004566:Electrodes; D011199:Potentiometry; D014920:Wine
chemical_list: D002244:Carbon; D003300:Copper
keywords: Copper sulfide; Labile copper; Screen printed electrode; Speciation; Stripping potentiometry; Wine