Ammonium nitrogen isotope ratios

Cifuentes, L. A., Fogel, M. L., Pennock, J. R., and Sharp, J. H. (1989). Biogeochemical factors that influence the stable nitrogen isotope ratio of dissolved ammonium in the Delaware Estuary. Geochim. Cosmochim. Acta 53, 2713—2721. 

Widory et al. [112] discuss the application of bulk carbon, nitrogen, oxygen, and hydrogen isotope ratio measurements to differentiate different groups of explosives (i.e., PETN,TNT, and ammonium nitrate/fuel oil [ANFO]). The authors also discuss the potential to discriminate samples of the same type of explosive where there are differences with respect to precursors, manufacturing processes, or year of manufacture. 

Isotopes are not expected to be absolutely identical in chemical properties (p. 247), but the difference is observable only in the light elements where the ratio of the mass of the isotopes is large, for instance and Thode and Urey (1939) concentrated nitrogen-15 in ammonium nitrate, to the extent of 70%, by allowing a solution of the salt to flow down a column against a counter current of ammonia. The equilibrium constant (p. 178) for... 

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