Novel calibration with correction for drift and non-linear response for continuous flow isotope ratio mass spectrometry applied to the determination of δ15N, total nitrogen, δ13C and total carbon in biological material†

Abstract

With automated analysis of a batch of samples using an elemental analyser isotope ratio mass spectrometer, the instrumental response is often non-linear (e.g., the isotope ratio varies with sample size) and is affected by changes over time (drift). Traditionally, drift and non-linearity effects are compensated for by including several reference samples in the batch with elemental masses, which closely match those of the samples. The novel calibration method presented here corrects for both drift and non-linearity, and thus allows for a wider range of sample masses in the batch, while accuracy and precision is maintained at the level attained by the traditionally accepted calibration procedure without increasing the number of reference samples.