No standard procedure to my knowledge, but for 13C content of particulate matter, I use a Sercon (formerly PDZ-Europa) EA-IRMS instrument. For 13C in the dissolved phase, things are more complicated, but you may look at the Picarro company (California, USA) that manufactures a laser absorption spectrometer and they also have a CO2 extraction module

To measure the 13C of organic matters by the EA-IRMS, I acidify by the solution to pH 2 with HCl to remove the CaCO3, after wash and  drying, I analyze by EA-IRMS the 13C of organic matters.

To analyze the 13C in Carbonates, in my laboratory we have a coupling Multiflow-IRMS. I attack  sediments with H3PO4 in 103 % (specific reaction H3PO4 with CaCO3), the CO2 stemming from the reaction I measure the 13C of carbonates.

For more information contact: http: // shiva.univ-tlse3.fr

Here is a solution practises (has a practice), if you have only the coupling EA-IRMS, you can proceed in this way:

- On a sample of homogeneous sediment you measure global 13C (carbonate + organic matters)

- On one other fraction acidified with the HCl with pH 2 and washed well and dried to measure you again the organic 13C.

From the intensities of peaks CO2, to calculate you the quantity of the CACO3 in your sediments.

So to calculate you the values of the 13C of carbonates.