Quantitative Analysis of Copolymers:  Influence of the Structure of the Monomer on the Ionization Efficiency in Electrospray Ionization FTMS

Abstract

The influence of the ionization efficiency on the measured copolymer sequence distribution is presented. Large differences in ionization efficiency were observed for mixtures of homopolyesters containing dipropoxylated bisphenol A/adipic acid and dipropoxylated bisphenol A/isophthalic acid and the corresponding copolyester dipropoxylated bisphenol A/isophthalic acid/adipic acid. The adipic acid structure has a higher affinity for the sodium cation, which results in more intense peaks for adipic acid containing oligomers. Relative sodium affinities of the oligomers were found to increase with an increasing number of acid end groups in favor of adipic acid containing oligomers. The ESI response of the oligomers depends on the polymer concentration in the sprayed mixture. This makes it impossible to correct for the ionization efficiency necessary for copolymer analysis. If differences in ionization efficiency are not corrected, the ion intensities in the copolymer mass spectra will show large deviations from the real composition and no conclusion can be drawn about the chemical (in)homogeneity of the MWD nor the random or block structure of the copolymer. This will also be valid for other cationization techniques like MALDI and FAB.

Compositional analysis of isobutylene/p-methylstyrene copolymers by matrix-assisted laser desorption/ionization mass spectrometry

“…To account for this difference in copolymer oligomer ionization, Koster and coworkers proposed the introduction of a relative ionization efficiency term, IE, in the calculation of the theoretical distribution when using chain statistics [27]. In this case, the calculation of theoretical oligomer intensities by Bernoullian statistics would need to be modified so that the intensity of a particular oligomer is not only determined by the mole fraction of the sample and the relative amounts of monomers, but is also dependent on the ionization efficiency of that oligomer.…”

A New Methodology for the Synthesis of Fluorinated exo‐Glycals and Their Time‐Dependent Inhibition of UDP‐Galactopyranose Mutase

“…Hence, selective ionization of certain components often occurs at the cost of other species and the obtained spectra are far from representative for the total sample composition; the increased complexity of the spectra not even being mentioned. It should also be mentioned that not all species are easily ionized, either by MALDI or ESI 34. Therefore, some species might not be observed at all in respective LC/MS chromatograms or mass spectra, but this is not often reported.…”

Treatment of an iatrogenic femoral artery pseudoaneurysm with concomitant arteriovenous fistula with percutaneous implantation of an amplatzer vascular plug

“…The data from the presented LC/MS spectrum, in terms of relative intensities of the observed peaks, should be considered only as a qualitative evidence for the polymer mixture composition and not as a quantitative one because there is a possible variation of the ionization efficiency as a function of the molecular weight of the polymer chains, the charge state of the adduct ion and the nature of the end groups 39…”