Thermally based isotopic speciation of carbon in complex matrices: a tool for environmental investigation

Elemental and isotopic analyses of carbon in environmental matrices usually highlight multiple pools of different composition and 13C/12C (δ13C ‰) isotopic ratio. Interpretation necessarily needs the characterization of the diverse end-members that usually are constituted by inorganic and organic components. In this view, we developed a routine protocol based on coupling of elemental and isotopic analyses that is able to discriminate the inorganic (IC) and organic (OC) contributions to the total carbon (TC) content. The procedure is only based on thermal destabilization of the different carbon pools and has been successfully applied on different environmental matrices (rocks, soils, biological samples) with a mean C elemental and isotopic recoveries of 99.5% (SD = 1.3%) and 0.2‰ (SD = 0.2‰), respectively. The Thermally Based Speciation (TBS) lead us to define precise isotopic end-members, which are unaffected by any chemical treatment of the sample, to be used for accurate mass balance calculation that represents a powerful tool to quantify the distinct carbon pools. The paper critically evaluates the method explaining the potentials and the current limits of the proposed analytical protocol.