Determination of the Molecular Mass Distribution of Narrow Polydispersity Polystyrene by MALDI-TOF-MS: Interlaboratory Comparison

Published

March 1, 2000

Author(s)

Kathleen M. Flynn, S Wetzel, William E. Wallace, William R. Blair, R J. Goldschmidt, David L. VanderHart, B M. Fanconi

Abstract

NIST has sponsored a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) interlaboratory comparison using a well-characterized polystyrene to determine the reproducibility in determining the molecular mass distribution. Samples of a well?characterized low molecular mass polystyrene were sent to any institution requesting it. A total of 18 institutions participated. The polystyrene was synthesized to have a tertiary butyl endgroup at one end and a proton at the other. NMR characterization of Mn was found to give (7050 400) u. The Mw was found to be (7300 600) u by light scattering. FTIR confirmed the presence of the two end groups and no others in measurable amounts. SEC was used to insure vial-to-vial homogeneity in the samples distributed to participants. Each participating laboratory was asked to perform MALDI mass spectrometry using two distinct protocols. Each laboratory was asked to do three repeats of each protocol to check for intralaboratory variability.By compiling all the returned data using all protocols into one preliminary analysis it was found that MALDI mass spectrometry returned an Mn of (6600 100) u and an Mw of (6700 90) u. These numbers were below those of the classical methods but still within the overlapping uncertainty ranges. The statistical uncertainty in the mass spectrometry measurements was very small indicating that from lab to lab reproducibility was extremely good. There was no statistical difference between the use of linear or reflectron time-of-flight instruments.In order to facilitate a more general comparison of the data, that is something beyond comparing moments of the distributions, the data from each participant was placed into 11 bins of equal width spanning the entire mass range of interest. By comparing the percent of signal in each bin a statistical measure of the differences in the shapes of the mass distributions could be determined. From this analysis it was apparent that very differently shaped distributions could yield essentially the same moments of the molecular mass distributions.

Proceedings Title

American Chemical Society; Division of Polymer Chemistry, Meeting | | | American Chemical Society

Volume

41

Issue

No. 1

Conference Dates

March 1, 2000

Conference Location

Undefined

Conference Title

Polymer Preprints

Pub Type

Conferences

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Keywords

intralaboratory comparison, MALDI, mass spectrometry, matrix-assisted laser desorption/ionzati, molecular mass distribution, synthetic polymer

Citation

Flynn, K. , Wetzel, S. , Wallace, W. , Blair, W. , Goldschmidt, R. , VanderHart, D. and Fanconi, B. (2000), Determination of the Molecular Mass Distribution of Narrow Polydispersity Polystyrene by MALDI-TOF-MS: Interlaboratory Comparison, American Chemical Society; Division of Polymer Chemistry, Meeting | | | American Chemical Society, Undefined, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851652 (Accessed April 28, 2025)