Sensitivity analysis for speciated isotope dilution mass spectrometry

Speciated isotope dilution mass spectrometry is a technique that uses mass spectrometer readings to determine the species-specific isotopic profile of a chemical element in solution. The problem admits several approaches, each with its own computational quirks. In our view, matrix methods are attractive because they are conceptually clear, easy to implement, and amenable to formal analysis. The purpose of this note it to illustrate these virtues by using a matrix method to analyze the numerical sensitivity of a particular published example under both observation noise and changes in parameter space. The analysis blends numerical and theoretical techniques, and has implications both for experimental design and for practical uncertainty assessment.