>Can anyone out there offer any suggestions as to how to remove inorganic S
>from marine organic matter sample?  We are trying to prepare samples of
>sediment, plant and animal samples for analysis of S isotope ratios of
>organic matter, and wish to avoid contamination by SO4, pyrite, etc.
>Thanks for your assistance.

The hard (and may be only) way of doing this is sequential extraction and
removal of (1) inorganic sulfate (e.g. phosphate extraction), (2) acid
volatile sulfur (mainly monosulfides) with subsequent removal of the acid
soluble sulfur fraction, and (3) chromium reducible sulfur (pyrite sulfur).
The remaining sample, which contains only organic sulfur compounds, can be
treated with any method suitable for extracting total sulfur. The produced
BaSO4 or Ag2S can be analyzed mass-spectrometrically giving you the sulfur
isotope composition of the organic sulfur fractions.  For a detailed
description check:
Wieder, Lang and Granus: An evaluation of wet chemical methods for
quantifying sulfur fractions in freshwater wetland peat. Limnol. Oceanogr.
30: 1109- (1985). We adapted their techniques for studying the isotopic
compositions of various S compounds (including two organic sulfur
fractions) in sediments of acid mine drainage lakes with resonable success.

I hope that helps,

Bernhard


Dr. Bernhard Mayer
Stable Isotope Laboratory
Department of Physics & Astronomy
The University of Calgary
2500 University Drive NW
Calgary, Alberta
Canada T2N 1N4
phone: (403) 220 5389 (office)
phone: (403) 220 6813 (lab)
fax:   (403) 220 7773 (lab)
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