Method of multiple spiking isotope dilution mass spectrometry

A method of multiple spiking isotope dilution mass spectrometry comprising:

• obtaining a mass spectrum of a chemical system having two or more inter-converting analytes of interest, the chemical system having been spiked with known amounts of isotopes of the analytes;
• determining systematic instrument biases corrected values of a mass spectrometric parameter of the analytes from the mass spectrum of the spiked chemical system;
• determining pure component contribution coefficients for each analyte in the mass spectrum by mathematically deconvoluting the corrected values of the mass spectrometric parameter using pure component mass spectra of the analytes, wherein deconvolution is performed according to a matrix expression relating the corrected values of the mass spectrometric parameter to a linear combination of the pure component mass spectra and the pure component contribution coefficients for each analyte;
• determining a property of one or more of the analytes in the chemical system from the pure component contribution coefficients determined for each analyte;
• and,
• estimating uncertainty in the property including estimating an increase in the uncertainty due to inter-conversion of the analytes.