Matrix-assisted laser desorption/ionization, fast atom bombardment and plasma desorption mass spectrometry of polyethylene glycol esters of (2-benzothiazolon-3-yl)acetic acid
Universität Konstanz, Constance, Baden-Württemberg, GermanyJournal of Mass Spectrometry (Impact Factor: 2.38). 06/2001; 36(6):626-32. DOI: 10.1002/jms.162
Fast atom bombardment (FAB), matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and plasma desorption (PD) mass spectra of newly synthesized polyethylene glycols (PEGs), (M(w) 600-4000 Da) chemically modified with biologically active (2-benzothiazolon-3-yl)acetyl end-groups are described (products 1-6). The spectra were also used for the determination of the molecular mass characteristics (number average (M(n)) and weight average (M(w)) molecular masses) of the initial and modified PEGs. As expected, M(n) and M(w) of the modified samples are higher than those of the non-modified samples. However, it is shown that molecular mass dispersity (determined by the comparison of the polydispersity indices (PDI = M(w)/M(n)) of both types of PEGs) essentially do not change during this modification. The FAB mass spectra, together with molecular species, show the presence of abundant [M + Na](+) ions of product 1 and [M + Na + H](+) species of 2 and 3, and [M + Na + 2H](+) of product 4. Two main series of fragment ions, derived from the cleavage of the ether bonds, are observed. The number fractions of the molecular adduct ions and fragment adduct ions, determined from the FAB and PD mass spectra of the modified PEGs, are compared. The MALDI-TOF mass spectra of compounds 1-6 show the presence of two series of polymers. The most abundant peaks are due to [M + Na](+) and [M + K](+) ions originating from the polymers, in which the two terminal hydroxyl groups of PEGs are esterified with (2-benzothiazolon-3-yl)acetic acid. The less abundant peaks are due to the monosubstituted polymers.
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ABSTRACT: (2-benzothiazolon-3-yl)acetic acid–telechelic poly(ethylene oxide)s (1 100–4 440 Da) with narrow molecular mass distributions (MMD) were analysed by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and size exclusion chromatography (SEC). The average molecular masses (M̄n and M̄w) determined by both methods were compared and a good agreement established. The cutting of the low molecular part of the initial poly(ethylene glycol) MMD during purification and isolation of the produced telechelic poly(ethylene oxide)s was proved. For this reason, the degree of esterification (x) of poly(ethylene glycol) (PEG) with (2-benzothiazolon-3-yl)acetic acid was calculated by MALDI-TOF MS and SEC, using additional UV data. The two series of x values derived from the M̄n-values, determined by the two methods, are very close. All of them are less than unity and the differences between the two types of x values decrease with the PEG molecular mass growth.
Article: Mass spectra of copolymers[Show abstract] [Hide abstract]
ABSTRACT: 1 Recent and older literature (covering the last 12–13 years) in the field of mass spectra of random and block copolymers is reviewed. A detailed description is given of the information on copolymer properties that can be recovered from the analysis of the low-mass region of the spectrum (the region below 500 Da) and the high-mass region. The features of mass spectra of copolymers obtained by different synthetic routes are discussed, such as free radical, condensation, ring-chain equilibration, microbial synthesis, ring-opening, simple anionic, cationic, Ziegler-Natta, and/or metallocene catalysis, along with some random and block copolymers that occur in Nature. The emphasis is on copolymer composition and average molar mass determination, and on the benefits of coupling mass spectrometry (MS) with separation techniques such as size-exclusion chromatography (SEC) and high performance liquid chromatography (HPLC). © 2002 Wiley Periodicals, Inc., Mass Spec Rev 21:108–144, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mas.10021
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