Derivatization of Low Molecular Weight Polymers for Characterization by Matrix-assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

✍ Scribed by John P. Barry; William J. Carton; Kristen M. Pesci; Rana T. Anselmo; Douglas R. Radtke; James V. Evans

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 191 KB
• Volume: 11
• Category: Article
• ISSN: 0951-4198
• DOI: 10.1002/(sici)1097-0231(199703)11:5<437::aid-rcm894>3.0.co;2-1

✦ Synopsis

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) is shown to give inaccurate results for the analysis of low molecular weight ethoxylate polymers. It is demonstrated that when the degree of ethoxylation is low (n < 9), MALDI-TOFMS produces substantially higher values for the number-average molecular weight (M n ) than obtained with more classical methods such as NMR spectrometry and a wet chemical method to determine the hydroxyl number. Apparently, this is the result of discrimination of the former technique against lower molecular weight ethoxylates in a polymer distribution. The results presented in this paper demonstrate this discrimination through the analysis of a series of ethoxylates with progressively lower M n values. It was also found that by derivatization of the polymer with phthalic anhydride, to produce the carboxylate derivative, the discrimination is reduced and data obtained with MALDI-TOFMS match more precisely the results obtained with the other methods.