Measurement of Tl(III/I) electron self-exchange rates using enriched stable isotope labels and inductively coupled plasma mass spectrometry

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Date: Nov. 1, 1995
From: Analytical Chemistry(Vol. 67, Issue 21)
Publisher: American Chemical Society
Document Type: Article
Length: 196 words

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Abstract :

An approach is described for measuring electron self-exchange rate constants ([k.sub.11]) in solution based upon stable isotope-labeled reactants, chemical separations, and inductively coupled plasma mass spectrometry. The technique is demonstrated for the exchange between [Tl.sup.III] and [Tl.sup.I] aquo ions in aqueous HCl[O.sub.4]. [Tl.sup.III] is prepared using 203Tl-enriched [T1.sub.2][O.sub.3] (203Tl abundance, [approximately]36%), and [Tl.sup.I] is prepared from natural abundance Tl reagents (natural 203Tl abundance, 29.52%). The exchange is monitored by mixing the labeled and unlabeled reactants and performing timewise separations through selective precipitation of [Tl.sup.I] as TlBr. Isotope abundances are measured in the TlBr precipitate and [Tl.sup.III] solution phases using ICPMS with minimal sample preparation; an NIST 981 (common lead) spike is added, and the 208Pb/206pb is measured as an internal standard to correct for mass discrimination. The self-exchange rate constant is determined from a McKay plot obtained from the 205Tl abundances of either oxidation state. A [k.sub.11] of (1.0 [+ or -] 0.1) x [10.sup.-4] [M.sup.-1] [S.sup.-1] was obtained in 1.5 M aqueous HCIO4 at 25 [degrees] C. The obtained [k.sub.11] compares favorably to a value of 1.1 x [10.sup.-4] [M.sup.-1] [s.sup.-1] based upon a previously published study of this exchange reaction using radiolabeled (204Tl) reactants.

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Gale Document Number: GALE|A17822730