We have been running organic carbon on Lake Michigan and Green Bay
sediments by acidifying the weighed sample in tin boats using 3N H3PO4,
the sample is then desicated over night and run the next day. The H3PO4
does not immediatly react with the tin but if they sit more than over
night the boats become brittle and cannot be holded up. The idea is that
H3PO4 will not react with the labile carbon as HCl does. We have not
tested this against another method to see if there are differences.

Pat Anderson
Great Lakes WATER Institute
University of Wisconsin-Milwaukee