Changes in Post-Source Decay Fragmentation Behavior of Poly(Methyl Methacrylate) Polymers with Increasing Molecular Weight Studied by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

2003 ◽  
Vol 9 (3) ◽  
pp. 195-201 ◽  
Author(s):  
Olli Laine ◽  
Sarah Trimpin ◽  
Hans Joachim Räder ◽  
Klaus Müllen
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Laser Desorption ◽  
Laser Desorption Ionization ◽  
Post Source Decay ◽  
Ionization Time ◽  
Fragmentation Behavior ◽  
Desorption Ionization ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

In order to investigate the systematic changes in fragmentation behavior of poly(methyl methacrylate) (PMMA) with increasing molecular weight, alkali–metal cationized PMMA 20-mer, 60-mer and 100-mer were selected for post-source decay (PSD) fragmentation study by matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry. PMMA polymers were cationized with lithium, potassium and cesium cations to explore the influence of the cation size on the fragmentation behavior of the polymers. All PMMA polymers could be fragmented by MALDI-PSD and fragmentation of the MALDI ionized synthetic polymer of molecular weight 10 kDa is reported here for the first time. It was shown that an increasing molecular weight of the PMMA chain required an increase in the size of the cation to improve the intensity and the number of the fragments in the PSD spectrum. Some instrumental parameters had to be optimized prior to a successful PSD analysis of the largest PMMA polymers.

Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Studies of Low Molecular Weight Dendrimers

2003 ◽  
Vol 9 (3) ◽  
pp. 203-211 ◽  
Author(s):  
Zhenwen Zhao ◽  
Shaoxiang Xiong ◽  
Xiangwen Liu ◽  
Bin Xin ◽  
Guanghui Wang
Keyword(s):  
Mass Spectrometry ◽  
Molecular Weight ◽  
Time Of Flight ◽  
Laser Desorption ◽  
Low Molecular Weight ◽  
Laser Desorption Ionization ◽  
Ionization Time ◽  
Desorption Ionization ◽  
Matrix Assisted Laser ◽  
Matrix Assisted Laser Desorption

We report the application of matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry, with delayed extraction in the reflectron mode, for the characterization of low molecular weight dendrimers. 20 dendrimer samples were measured and 4 typical dendrimers, as examples, are discussedin detail. Several factors that affect the analysis including the matrices used, the concentrations of sample, the solvents and cationization reagent used, were investigated in detail. Experimental results indicate that the type of solvent can greatly influence exact mass measurement. However, sample preparation is generally not very critical for dendrimer analysis using MALDI-ToF since many kinds of matrices and a wide range of sample concentrations can be used efficiently. In addition, the Cs+ ion can be used to enhance the efficiency of cationization. Some reasons for this behavior are discussed on the basis of results of calculations using Gaussian94 software (a connected system of programs for performing a variety of semi-empirical and ab initio molecular orbital (MO) calculations).

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