title: Application of a poly(4-styrenesulfonate) liquid binding layer for measurement of Cu2+ and Cd2+ with the diffusive gradients in thin-films technique.
abstract: A diffusive gradients in thin films (DGT) technique for measuring Cd and Cu is described using, for the first time, a liquid phase binding layer and a dialysis membrane diffusive layer. The binding phase was a 0.020 M solution of poly(4-styrenesulfonate) (PSS) polyelectrolyte using a specially designed DGT deployment device. The binding properties of Cd2+, Cu2+, and a range of alkali and alkaline earth metal ions to the PSS solution were characterized. The PSS behaved like a cation exchanger with preferential binding to Cd2+ (6.0 micromol mL(-1), log K = 9.0) and Cu2+ (2.5 micromol mL(-1), log K = 8.1) under competitive binding conditions. PSS had a substantial binding capacity at pH > 3 and at competitive Na+ concentrations up to 1.0 M. The DGT devices were successfully validated for Cd2+ (accumulated mass vs time r2 = 0.969, recovery compared with predicted values = 98%) and Cu2+ (r2 = 0.980, recovery = 98%) in synthetic lake water (Windermere). Validation was also undertaken for Cu in a spiked local lake water (Parkwood Pond) (r2 = 0.981, recovery = 46%). The low recovery here was due to complexation of Cu by natural organic matter (14 mg C L(-1)). Field deployments of the DGT devices were successful at measuring Cu concentrations of 0.031-0.63 microg L(-1) in local fresh and salt waterways. These DGT-labile measurements were 0.05-39% of the 0.45-microm-filtered Cu values.
authors.affiliation: School of Environmental and Applied Sciences, Griffith University Gold Coast Campus, PMB 50 Gold Coast Mail Centre, Queensland 9726, Australia.
authors.forename: Weijia
authors.initials: W
authors.lastname: Li
authors.forename: Peter R
authors.initials: PR
authors.lastname: Teasdale
authors.forename: Shanqing
authors.initials: S
authors.lastname: Zhang
authors.forename: Richard
authors.initials: R
authors.lastname: John
authors.forename: Huijun
authors.initials: H
authors.lastname: Zhao