Organic Solids Analysis Techniques
Carbon and nitrogen isotopes techniques
Organic solids are weighed into tin capsules. Calibrated internal standards are prepared with every batch of samples for normalization of the data. In general, 100µg of N are required for analysis. The carbon can be diluted with helium when there is higher %C than %N as is usually the case. Elemental analysis must be performed first if the quantities of carbon and/or nitrogen in a sample are unknown.
The isotopic composition of organic carbon and nitrogen is determined by the analysis of CO2 and N2 produced by combustion on an Elementar Isotope Cube Elemental Analyser followed by "trap and purge" separation and on-line analysis by continuous-flow with a DeltaPlus Advantage isotope ratio mass spectrometer coupled with a ConFlo III.
For difficult materials such as soils or filters, up to 200mg of material can be handled in a single sample with at least double that amount of tungstic oxide (WO3).
The routine precision of the analyses is 0.20‰.