Quantitative analysis of broad molecular weight distributions obtained by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

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Eur. J. Mass Spectrom. 2, 161 - 165 (1996)

Quantitative analysis of broad molecular weight distributions obtained by matrix-assisted laser desorption ionisation-time-of-flight mass spectrometry

J. Spickermann, K. Martin, H.J. Räder and K. Müllen
Max-Planck-Institut fur Polymerforschung, Ackermannweg 10, D-55128 Mainz, .
H. Schlaad and A.H.E. Müller^*
Institut für Physikalische Chemie, Universität Mainz, Welderweg 15, D-55099 Mainz, .
R.-P. Kruger
Institut für Angewandte Chemie Berlin-Adlershof eV, Rudower Chaussee 5, D-12489 Berlin, .

ABSTRACT:

In order to quantify the error of matrix-assisted laser desorption ionisation (MALDI) time-of-flight (TOF) mass spectrometry in the determination of broad molecular weight distributions, different mixtures by weight of two poly(methyl methacrylate) standards were prepared. These mixtures, with well-defined bimodal molecular weight distributions were analysed by MALDI-TOF mass spectrometry using different matrices (2,4,6-trihydroxyacetophenone and 2,5-dihydroxybenzoic acid) and different cations (Li⁺, Na⁺,K⁺, Rb⁺ and Cs+) for doping the analyte. From the MALDI-TOF mass spectrometric data, the weight fractions of the two polymers of all mixtures were determined and compared to the values measured by size-exclusion chromatography. The results show that it is possible to obtain the correct M_n and M_w values with 2,5-dihydroxybenzoic acid as matrix and K⁺ as cationisation metal.

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