δ13C, δ15N or δ34S in bulk solid materials
Sample material: Any solid that can be combusted at 1020°C and that contains sufficient C, N or S. Typical sample types are rocks, plants, animal tissues.
Precision: Typically < 0.3 permil for δ13C and < 0.3 permil for δ15N
Instrument: Thermo Scientific Delta V+ connected to a Flash 1120 Elemental Analyzer and a Flash HT
Sample requirements: Typically, we need >50 µg C, N and S. Sample sizes and other requirements may vary greatly on the sample material and the experiment requirements. We recommend that you contact us for discussion and advice about ideal sample sizes.
Routines: Sample preparation depends greatly on type of sample and purpose of analyses. Generally, all samples are homogenized (e.g. by grinding in a mortar) and dried (60-80°C). Soils, sediments, rocks or animals containing carbonates needs carbonate removal (acid washing) before analysis of δ13C in organic C. One might also want to remove fat from tissue with significant fat as fats and proteins often have different δ13C. For particulate organic carbon samples or other samples collected on filters, C, N and S free filters must be used, preferably ignited quarts filters.
Samples are then weighed (0.1 - 10 mg depending on material) into tin or silver capsules before analyses. The capsules are dropped into a furnace containing metallic catalysts at 1020°C with a pulse of O2 where samples oxidize to CO2, N oxides and SO2. The gasses are passed through a reactor with reduced copper reducing Noxides to N2 and a water trap. The gasses are separated in a packed GC column before they are passed to the isotope ratio mass spectrometer.