Determination of nitrogen-15 at sub-microgram levels of nitrogen using automated continuous-Flow isotope ratio mass spectrometry

Recent developments in continuous-flow isotope ratio mass spectrometry have considerably enhanced the ability to make rapid and precise measurements of the stable isotope ¹⁵N. Although the amounts of nitrogen required for precise analyses have been reduced considerably, the levels required remain a limitation for many applications. A simple manipulation of the use of commercially available equipment is described that allows the simultaneous determination of nitrogen and ¹⁵N at levels as low as 10 nmol of total nitrogen.