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Pretreatment of Nitric Acid with Hydrogen Peroxide Reduces Total Procedural Os Blank to Femtogram Levels

Determining and correcting for background contributions of Re and Os from chemical reagents is critical for accurate and precise Re–Os dating of materials with parts per billion to parts per trillion Re and Os concentrations. Here we investigate reducing Os content in nitric acid, as it is the main contributor to the Os blank. Pretreating high-purity nitric acid with hydrogen peroxide (H2O2) significantly reduces nitric acid’s Os contribution to femtogram levels, greatly reducing Os blank corrections. The improvement in background Os allows analysis of samples with extremely low Os concentrations (into the low ppt level). We present experimental data identifying key factors in reducing Os blank, including nitric acid to hydrogen peroxide volume ratios, wet versus dry glassware, and dark versus lighted reaction environments. These variables affect the reaction time between the two reagents, which in turn correlates inversely with the final Os content. The volume ratio of H2O2/HNO3 is shown to be the fundam...

Authors:   Gang Yang; Aaron Zimmerman; Holly Stein; Judith Hannah
Journal:   Analytical Chemistry
Year:   2015
DOI:   10.1021/acs.analchem.5b01751
Publication date:   09-Jul-2015
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