Dear Benoit,

     We have seen d34S values around 20 per mil in kelp, fish fertilizer,
and marine fish tissue, likely originating from the sulfur isotopic value
of marine sulfate.  You could homogenize and calibrate one of these types
of materials for use as a working standard.  One method of converting the
organic sulfur to sulfate for the purpose of calibration against available
inorganic standards is by using a Parr Bomb.  --  Steve

On Fri, Dec 14, 2018 at 9:09 AM Benoit Lebreton <[log in to unmask]>

> Dear all,
> We are looking for an organic standard for d34S measurements with a value
> close to 20 pm ? We only found inorganic standards so far. Does anyone know
> about such a standard and where to buy it ?
> Many thanks in advance,
> Benoit

Steven Silva
U.S. Geological Survey
345 Middlefield Rd., M/S 434
Menlo Park, CA 94025

ph:  (650) 329-4558
fax: (650) 329-5590