We want to analyse Total Carbon (CTotal) Total Organic Carbon (TOC), Total Nitrogen (TN), d13Corg and d15N in sediment core collected from Mumbai Harbour Bay. Previous study had shown organic carbon content in the range 2-5 %.
Various methods have been described in literature for removal of inorganic carbon. The collected core samples have been stored in freezer. I have planned following steps for our measurement:

For total C, TN, d15N: Dry samples at 500C, power it and measure in EA-IRMS.

For organic carbon and d13Corg : 0.5 g of sample (stored in freezer) and treat with 1M HCl and heat at 500C. Repeat the process till effervescence seized. 

Please suggest if any modification required in the above steps.

Whether heating samples at 500C will affect the isotope ratio?