Determination of nitrogen-15 by optical emission spectrometry using an atomic absorption spectrometer

Abstract

The determination of ¹⁵N percentage abundance by optical emission spectrometry (OES) using an atomic absorption spectrometer (AAS) with an inexpensive radiofrequency generator (27.5 MHz, 20 W) and a specially designed cavity is described. Sample tubes for micro-Dumas combustion are easily constructed as required and nitrogen spectra, in duplicate for each sample, are recorded in 20 s for two-peak or 30 s for three-peak spectra. Because of the cavity design the technique tolerates masses of N per sample tube between 1 and 110 µg. The precision, coefficient of variation <6%, is equivalent to that reported for other OES techniques and statistical analysis suggested that a large proportion of the analytical variability is introduced during sample preparation. Many laboratories have access to AAS and this, together with the cavity and inexpensive r.f. generator, makes ¹⁵N technology widely available at low cost.