title: Spectroscopic and electrochemical evaluation of a perfluorosulfonated ionomer and its gel as preconcentrating media for [ReI(DMPE)3]+, where DMPE = 1,2-bis(dimethylphosphino)ethane.
abstract: The interaction of [ReI(DMPE)3]+, where DMPE = 1,2-bis(dimethylphosphino)ethane, a nonradioactive analogue of a heart imaging agent, with Nafion gel, which is Nafion plasticized with tri-n-butyl phosphate, has been evaluated spectroscopically and electrochemically. Thin-layer spectroelectrochemistry on the rhenium compound yields a linear Nernst plot with an n value of 0.99 and E degree' of 0.049 V vs Ag/AgCl. The electrochemistry is consistent with a reversible one-electron transfer between the mono- and dicationic forms of the complex. The UV-visible spectrum of electrogenerated [ReII(DMPE)3]2+ is identical to that obtained by air oxidation of [ReI(DMPE)3]+. Thin, free-standing films of Nafion gel and Nafion that were sufficiently clear to record visible spectra were cast. Spectroscopic measurement of the partitioning of [ReI-(DMPE)3]+ from aqueous solution into these films shows a more rapid uptake of the complex by the Nafion gel. Preconcentration factors into Nafion gel and Nafion were 350 and 50, respectively, after 4 h of soaking. Cyclic voltammetry of 1.0 x 10(-4)-1.0 x 10(-7) M (ReI(DMPE)3]+ in 0.15 M supporting electrolyte aqueous solution at bare gold and spectroscopic graphite electrodes suggests that the complex adsorbs to these electrodes. By comparison, the well-defined cyclic voltammograms at Nafion gel-modified electrodes exhibit diffusion-controlled behavior. The formal reduction potential at Nafion gel-modified electrodes is shifted positively compared to bare electrodes. A current enhancement of approximately 4 was observed at Nafion gel-modified spectroscopic graphite over a bare electrode. A calibration plot of peak current for differential pulse voltammetry vs concentration at Nafion gel-modified spectroscopic graphite was linear in the 10(-7)-10(-5) M concentration range, with a detectable signal down into the 10(-9) M range.
authors.affiliation: Department of Chemistry, University of Cincinnati, Ohio 45221-0172, USA.
authors.forename: B H
authors.initials: BH
authors.lastname: Swaile
authors.forename: E A
authors.initials: EA
authors.lastname: Blubaugh
authors.forename: C J
authors.initials: CJ
authors.lastname: Seliskar
authors.forename: W R
authors.initials: WR
authors.lastname: Heineman
mesh_terms: D004563:Electrochemistry; D005465:Fluorocarbon Polymers / Q000737:chemistry*; D005782:Gels; D017736:Ion-Selective Electrodes; D009942:Organometallic Compounds / Q000737:chemistry*; D010755:Organophosphates / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D019275:Radiopharmaceuticals / Q000737:chemistry*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005465:Fluorocarbon Polymers; D005782:Gels; D009942:Organometallic Compounds; D010755:Organophosphates; D010720:Phosphines; D019275:Radiopharmaceuticals; D012996:Solutions; C109630:tris(1,2-bis(dimethylphosphino)ethane)rhenium(I); C040402:perfluorosulfonic acid; C009524:tributyl phosphate