Comparative studies of poly(dimethyl siloxanes) using automated GPC-MALDI-TOF MS and on-line GPC-ESI-TOF MS

Abstract

In this study we compare on-line gel permeation chromatography (GPC) electrospray ionization (ESI) time-of-flight (TOF) mass spectrometry (MS) to automated GPC matrix assisted laser desorption ionization (MALDI) TOF MS for poly (dimethylsiloxane) (PDMS) analysis. Average mass values for a hydroxyl-terminated PDMS (OH-PDMS) sample were obtained and compared to traditional GPC that was calibrated with narrow polystyrene standards, by direct ESI and MALDI MS analysis, by a summation of mass spectra of all GPC fractions, and also by the recalibration method determined by both mass spectrometric methods. Quantitatively, the difference noted here between these hyphenated techniques is that GPC-ESI-TOF MS effectively reports the low-mass oligomers and underestimates the high-mass oligomers, while GPC-MALDI-TOF MS effectively reports the high-mass oligomers and underestimates the low-mass oligomers. In the GPC-ESI-TOF MS experiments, ion current suppression was observed in the high molecular weight region. The suppression effect was confirmed by repeatable sample runs and by injecting different PDMS samples. Higher chromatographic resolution was observed for GPC-ESI-TOF MS compared to GPC-MALDI-TOF MS. In fact, truly mono-disperse oligomers were observed in the low molecular weight range from GPC-ESI MS experiments. (J

Chemical Detectors

“…The electrospray technique was found to be more effective at reporting low-M oligomers; the hyphenated MALDI technique was better at characterizing high-M oligomers [17]. The electrospray technique was found to be more effective at reporting low-M oligomers; the hyphenated MALDI technique was better at characterizing high-M oligomers [17].…”

Coupling of size‐exclusion chromatography with electrospray ionization charge‐detection mass spectrometry for the characterization of synthetic polymers of ultra‐high molar mass

“…After correction of the elution times for the delay between the RI and MS signals, Log(M i ) values are plotted versus elution volumes (which are directly obtained from the corrected elution times). Using the MS‐generated internal calibration curve and the RI response for quantification, accurate MWD parameters that compared well with those obtained from the traditional approach were reported . For example, the M n value calculated by the online SEC/ESI‐MS analysis of a methyl‐terminated poly(dimethylsiloxane) sample was found to deviate by less than 1.0% from the 3290 Da value obtained by SEC with triple detection, in great contrast with the 57.4% higher value determined after SEC calibration established with polystyrene standards .…”

Citric Acid Capped Iron Oxide Nanoparticles as an Effective MALDI Matrix for Polymers

“…Figure 5a demonstrates that the NPCA-NaOH matrix effectively desorbs/ionizes high molecular mass polymers such as 25 and 80 kDa PDMS. As Na + has been reported to assist PDMS ionization in MALDI [62], Na + present in the NPCA matrix is to serve as the cation source to form [C 3 H 9 Si(OSiC 2 H 6 ) n CH 3 + Na] + . The broad peak width typical for high mass MALDI [54,55] precludes repeating unit analysis of polymers.…”