Chapter 13 - Determination of the Abundance and Stable Isotopic Composition of Trace Quantities of C and N in Geological Samples: The Practice and Principles of Stepped-Heating at High Temperature Resolution

Abstract

This chapter determines the abundance and stable isotopic composition of trace quantities of carbon and nitrogen in geological samples. Stepped-heating technique is used to isolate different components and to measure their isotopic compositions. Stepped-heating techniques have evolved from simple experiments to the situation today where many steps are performed, with the operating conditions being strictly controlled. Carbon and nitrogen can both be present within geological samples in a variety of unrelated components that may have markedly different isotopic compositions. For both carbon and nitrogen, the systems that are used have four aspects in common: extraction (E), purification (P), quantification (Q) and mass spectrometry (M), to determine the isotopic composition of the element. The results obtained from pure samples and reference materials are modeled. This chapter describes the principles behind stepped-heating and the basic techniques employed to determine the isotopic composition of the element. When these techniques are combined with physical and chemical pre-treatments, it can be used to isolate and analyze trace components occurring within whole-rock samples. However, these techniques are best suited for pilot studies, experiments where only a very small amount of material is available for study, and specialized applications, such as the characterization of a new reference material.