We routinely analyze Os isotopes and concentrations in crushed rock powders. Our methods are focused on Os isotopes such that we isolate Os from samples and do not preserve other elements. However, if Os is critical to your work it may be worth analyzing the Os separately. If you are interested contact me offline and I can send you references on techniques from our lab.
Oxidized OsO4 does become volatile and escapes. To prevent Os loss, we extract Os from samples under pressure of N2 gas using a high pressure asher (HPAS) (https://www.anton-paar.com/us-en/products/details/high-pressure-digestion-hpa-s-high-pressure-asher/). Samples, loaded into quartz glass tubes with reverse aqua-regia, are sealed in the HPAS, pressurized with N2 gas to 100 bar and heated to 280 degrees for 12 hours. As soon as the samples are cooled and depressurized, the acid solution containing the oxidized Os undergoes solvent extraction to convert the Os into a more stable form. The Os partitions into carbon tetrachloride and then into concentrated hydrobromic acid where it is stable. We analyze Os isotope ratios using a thermal ionization mass spectrometer (TIMS) as negative ion OsO3-. This process does not provide 100% yield, but an isotope tracer added to the sample allows determination of Os concentration from measured isotope ratios by isotope dilution.
Dr. Staci Loewy
Isotope Geochemist and
MC-ICP-MS Laboratory Manager
The University of Texas at Austin
Department of Geological Sciences
2275 Speedway, Stop C9000
Austin, TX 78712-1722
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From: PLASMACHEM-L: Analytical Chem.(ICP's, DCP's, MIP's). <[log in to unmask]> On Behalf Of Paqui Polonio
Sent: Monday, May 14, 2018 8:52 AM
To: [log in to unmask]
Subject: Osmium stability analyses
We are analyzing some samples of pharmaceutical industry. We are having bad recoveries in the analysis of osmium. After searching the possible problem, we have reach the conclusion that when we digest the sample the osmium reacts in the oxidizing media giving OsO4(g). In the literature are given some possible solutions to this problem. Stabilizing the osmium with a solution of ascorbic acid or cysteine.
Does anyone use this to stabilize osmium? Wich concentration of ascorbic acir or cysteine should we use?
Do you know any other possible solution to this problem?
Thank you in advance.