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AIST TODAYNo.3 Winter 2002

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Formation of Large Cationized Molecules in Gas Phase
Hisashi TOGASHI
Metrology Institute of Japan
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Recently new ionization techniques for large molecules have been introduced into the field of mass spectrometry of solid samples. However, the mechanisms of ionization are not adequately understood for the establishment of quantitative analysis. In the investigation of cationization processes of fundamental non-ionic surfactants in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, we have found that cationization efficiency of poly(ethylene glycol) oligomers depends on the kind of metal ions while poly(propylene glycol) oligomers show little dependence. This act indicates that the chemical structure of chain is essential in the cationization process of linear molecules.
Figure
Mass spectrum of poly(ethylene glycol). Molecules of various size cationized by alkali ions (Li+,Na+,K+)are observed. The symbol n denotes the number of repeating units (-CH2CH2O-)

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