Hi Leon,


In answer to question #2, yes.


We routinely use sulfide, sulfate and pure S standards in a linear normalization with an R2> 0.99. For me, the slope is commonly 1.05 to 1.10, a much larger expansion coefficient that CN.


Best regards,





Benjamin Harlow

Manager, Stable Isotope Core Laboratory

Washington State University

367 Eastlick | Pullman, WA  99164-4236

Office: 509-335-6161 | Lab: 509-335-6154 | Fax:509-335-3184




From: Stable Isotope Geochemistry <[log in to unmask]> On Behalf Of Michalski, Greg M
Sent: Tuesday, October 13, 2020 4:50 AM
To: [log in to unmask]
Subject: Re: [ISOGEOCHEM] NBS 127 (BaSO4) and delta34S(VCDT) normalisations


NBS 127 is essentially seawater sulfate precipitated with Ba...If you have an ocean nearby

From: Stable Isotope Geochemistry <[log in to unmask]> on behalf of Leon Clarke <[log in to unmask]>
Sent: Tuesday, October 13, 2020 4:46 AM
To: [log in to unmask] <[log in to unmask]>
Subject: [ISOGEOCHEM] NBS 127 (BaSO4) and delta34S(VCDT) normalisations



I was in the process of purchasing NBS 127 (BaSO4, delta34SVCDT = +21.12 per mil), to use within a 3-point barium sulfate calibration including IAEA-SO-5 (+0.49 per mil) and IAEA-SO-6 (-34.05 per mil).

However, I have recently been informed that NIST have “pulled [NBS 127] from stock to undergo stability test due to it nearing the expiration date”. Consequently, I would appreciate it if anyone can comment on the following questions:

1.       Has anyone identified another enriched BaSO4, that is homogeneous w.r.t. to delta34SVCDT?


2.       Do the other enriched international standards (IAEA-S-4, elemental S, +16.90 per mil, and IAEA-S-2, Ag2S, +22.62 per mil) plot on a straight line with the three barium sulfate reference materials?


3.       Does anyone have any NBS 127 that they no longer have any use for? (I would be able to swap for another reference material.)

Many thanks in advance, Leon



Dr Leon J. Clarke

Senior Lecturer in Environmental Analytical Chemistry

Department of Natural Sciences

Faculty of Science and Engineering

Manchester Metropolitan University

John Dalton East

Chester Street

Manchester M1 5GD

United Kingdom


E-mail: [log in to unmask]


Tel: +44 (0)161 247 1412