Molecular Mass Distribution Measurement by Mass Spectrometry
William E. Wallace, Charles M. Guttman
This NIST Recommended Practice Guide presents a method using mass spectrometry to make a quantitative determination of the molecular mass distribution of narrow polydispersity synthetic molecular materials. The main obstacle for converting an oligomer-resolved mass spectrum (MS) into a valid molecular mass distribution (MMD) is the systematic uncertainty in the ion intensity axis of the mass spectrum. This guide demonstrates how to make gravimetric mixtures of analytes having the same general chemistry but differing in molecular mass distribution to 1) ascertain if mass bias is present for a given set of measurement conditions, 2) create a calibration curve to properly convert the MS to a valid MMD, and 3) determine systematic uncertainties for the calibration curve when certain specific conditions are met.