Instrumental determination of organic carbon in marine sediments

Methodology is presented for the first completely instrumental determination of organic carbon (OC) in marine sediments, using a carbon–hydrogen–nitrogen (CHN) analyzer for total carbon (TC) content and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) for inorganic carbon (IC) content. It utilizes direct calibration or standard addition in quantifying the carbonate combination band intensity at the energy near 2510 cm−1. Since no OC standard reference materials are currently available, we have compared the results for OC from the proposed method with those from more tedious methods, involving wet chemistry. No significant difference was found with determinations, employing the CHN analyzer together with acid-extract analyses by (i) an inductively coupled plasma atomic emission spectrometer (ICP-AES) and (ii) a dissolved organic carbon (DOC) solution analyzer, with the decarbonation mass change being taken into account for the method (ii) involving acid addition. The proposed DRIFTS method is cheap, rapid and nondestructive.