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Eur. J. Mass Spectrom. 4, 107 - 111 (1998) |
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| Liquid ionization mass spectrometry for reactions between formaldehyde oligomers and methanol in aqueous solutions | ||
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Takeo Kaneko, Peiming Yang and Masahiko Tsuchiya |
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| ABSTRACT: | ||
| Formalin used as a raw material for producing polymers contains poly(oxymethylene) glycols, HO(CH2O)nH (referred to as An). Since a small amount of methanol is added to the formalin, their monomethyl ethers, CH3O(CH2O)nH (referred to as Cn), also exist in formalin. The composition varies with temperature, pH etc. Liquid ionization (LPI) mass spectrometry was used to analyze this composition and the reactions between An and methanol. Protonated molecules of hydrated oligomers, An(H2O)mH+, and hemiformals, Cn(H2O)mH+ [CnWmH+], were observed in primary solutions, which were produced by dissolving paraformaldehyde in water in order to minimize the influence of Cn at the start. In the case of concentrated solutions (> 20%), thermal decomposition of An and the production of hemiformals (Cn) occurred during mass spectrometric measurement. It was found that acetone, vaporized near to the sample, was most effective in reducing such decomposition and formation of undesirable products. The molecular weight distribution of formaldehyde oligomers (An) obtained by this method were somewhat different from those obtained by other methods in that larger oligomers have not been observed. The reason for the differences is still under study. Chemical reactions were studied by adding methanol to the primary solution and by measuring LPI spectra of the mixture at intervals of time. Methanol reacted with An in the primary solution to form Cn over a time period of 100102 min at ambient temperature. LPI-MS provides useful information about reactions occurring in solution and also about hydration and solvation. | ||
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Keywords: Liquid ionization mass spectrometry, formaldehyde oligomers, reactions between formaldehyde oligomers and methanol in aqueous solutions, atmospheric pressure ionization, effect of matrix. |
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