Steven R. Silva Carol Kendall Greg Michalski Karen L. Casciotti Scott D. Wankel P. A. de Groot Cecily C.Y. Chang 2004 <p><span>This chapter reviews methods for analyzing "natural abundance" nitrogen-bearing compounds in water for δ</span>¹⁵<span>N, δ</span>¹⁸<span>O, and δ</span>¹⁷<span>O. The techniques that are reviewed are Kjeldahl distillation and digestion, diffusion, micro diffusion, ion exchange, and microbial denitrifier methods. It overlaps the contents of the preparation of ecological and biogeochemical samples for isotope analysis and also covers sections on particulate organic nitrogen and biological samples. Nitrogen comprises 78% of the atmosphere, oxygen 21% and argon 1%. There are two stable isotopes of N are&nbsp;</span>¹⁴<span>N and&nbsp;</span>¹⁵<span>N and a wide range of oxidation numbers exhibited by nitrogen compounds. Developments of continuous-flow mass spectrometry makes it possible to determine both δ15N and δ18O values of nitrate samples. Such techniques are particularly useful for small-size samples. With decreasing sample size, possible isotopic fractionations associated with extraction from the matrix, contaminants in the reagents, and leaks will become more significant. Due to the interest in distinguishing different species of organic-N compounds, the diffusion method is applied to differentiate types of organic-N.</span></p> application/pdf 10.1016/B978-044451114-0/50017-X en Elsevier Preparation and analysis of nitrogen-bearing compounds in water for stable isotope ratio measurement chapter