Quantitative time‐of‐flight secondary ion mass spectrometry of a perfluorinated polyether

Abstract

Quantitative determination of the molecular weight and composition of submicrogram of a perfluorinated polyether (PFPE) supported on Ag and Si substrates was from empirical relationships derived from the intensities of specific high‐mass (≥ 800 amu) fragmentation ions from time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) measurements. These relationships are explained in terms of simple concepts regarding the process of volatilization, fragmentation and ionization in TOF‐SIMS. The results for both negative and positive ions are nearly independent of the substrate materials used, demonstrating that the high‐mass fragmentation ions in TOF‐SIMS may be useful generally for in situ quantitative analysis of PEPEs on non‐specific substrates. This is an important difference between the TOF‐SIMS fragmentation spectrum and the complementary TOF‐SIMS cationized molecular ion spectrum, which requires special sample preparation and/or substrates. In order to interpret the quantitative information available in the TOF‐SIMS fragment spectrum, it was absolutely necessary to characterize extensively the PFPE samples using NMR and TOF‐SIMS Ag+ ‐cationized molecular ion results. This characterization helped to demonstrate the power of TOF‐SIMS to do quantitative analysis and led to additional insight concerning the SIMS ion‐forming process for PFPE. This study represents one of the first attempts to make quantitative use of the high‐mass fragment ion intensities in SIMS studies of polymers, and presents a method for confirming the origin of the mass peaks in the spectra. Copyright © 1991 John Wiley & Sons Ltd.