Diode Array Spectrometer for Nitrogen Isotopic Analysis

Abstract

The analytical precision for measurements of the isotopic composition of dinitrogen gas by emission spectrometry has primarily been limited by variability of the spectral background. Imaging the spectral region surrounding the isotopic bandheads with a diode array permitted a correction to be made for the background spectra and increased the statistical precision of the raw data. With the use of a multiple regression algorithm to process the spectral data, the standard deviation for an individual determination at the natural abundance level was 0.002 atom %. After an initial calibration, the standard deviation for measurements of the same sample, repeated over several years, remained at that level. In contrast to the case for commercial instruments, samples of widely varying mass can be readily analyzed. Further increases in precision are limited by an unidentified source of variance.