Due to its preferential enrichment in sulfidic sediments, V holds promise as a proxy for Earth’s oxygenation history. Unfortunately, full exploitation of the proxy is hampered because the chemistry governing V sequestration is poorly constrained. UV-vis spectra show that mildly alkaline and sulfidic test solutions initially containing μM concentrations of VVO43- produce polysulfides (Sx2-; x =2-6) at stoichiometric amounts consistent with VV reduction to thiovanadites (VIIIO3-xSx3-) and/or thiovanadyl ions (VIVO2+ or VIVS2+). This behaviour stands in stark contrast with that of Mo, Re, and W which all prefer thiolation over reduction to form thiometalates (e.g., MoVIS42-, ReVIIS4-, and WVIS42-) in similar solutions. Rather, V appears to mimic more closely the chemistry of its main group cohort, As, which is known to form thioarsenites (AsIIIO3-xSx3-) in sulfidic solutions. This research seeks to define the chemical controls on V speciation in sulfidic waters by quantifying stability constants for the formation of the various VIII, VIV, and VV species. Here, we report on methods developed using ion pair chromatography (IPC) with conductivity, UV-vis, and/or MS detection to separate, identify, and quantify V ions. Ultimately, the IPC methods will be combined with a suite of analytical techniques to characterize the aquatic and heterogeneous speciation of V in an array of test solutions over a wide range of conditions.

Ion Pair Chromatographic Separation of VV, VIV, and VIII Ions in Sulfidic Waters

2019 Spring National Meeting

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