Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) by external injection of matrix-assisted laser desorbed and ionized (MALDI) polymers offers good possibilities for characterization of low molecular weight homopolymers (MW range up to 10 kDa). The molecular masses of the molecular weight distribution (MWD) components of underivatized and derivatized (dimethyl, dipropyl, dibutyl and diacetyl) polyethylene glycol (PEG) 1000 and 4000 were measured by MALDI-FTICR-MS. These measurements have been performed using a commercial FTICR spectrometer with a home-built external ion source. MALDI of the samples with a 2,5-dihydroxybenzoic acid matrix in a 1000:1 matrix-to-analyte molar ratio produces sodiated molecules in a sufficient yield to trap the ions in the ICR cell. The masses of the molecular weight distribution of PEG components were measured in broad-band mode with a mass accuracy of < 5 ppm in the mass range around 1000 u and within 40 ppm accuracy around 4000 u. From these measurements, the endgroup mass of the polymer was determined by correlation of the measured component mass with the degree of polymerization. The masses of the PEG endgroups have been determined within a deviation of 3-10 millimass units for the PEG1000 derivatives and 10-100 millimass units for the PEG4000 derivatives, thus confirming the identity of the distal parts of the model compounds.

The photodegradation of indigo has been studied with emphasis on the degradation products. Ultraviolet–visible spectrometry, high performance liquid chromatography and direct temperature‐resolved mass spectrometry were employed for the characterisation of aged samples. Indigo, isatin, isatoic anhydride, anthranilic acid and indirubin were detected, together with other unidentified compounds. A new degradation product, tryptanthrin, was identified by both high performance liquid chromatography and mass spectrometry techniques, and two other possible degradation products have also been suggested. The degradation of synthetic and natural indigo has been compared and an explanation for the higher rate of degradation of natural indigo proposed.

No abstract

Sumatra benzoin resins originating from two species of Styrax were studied using modern analytical techniques. Analysis of these types of resins usually involves several steps including alkaline hydrolysis, derivatization of the polar groups and chromatography. Two different resins, and three different qualities from each resin, were investigated using a fast analytical method which omits the hydrolysis step and makes it possible to identify all of the individual components of the resin in one gas‐chromatography–mass spectrometry measurement. Resins from both Styrax benzoin Dryand and S. paralleloneurum Perk contain free cinnamic and benzoic acids and their corresponding esters with p‐coumaryl and coniferyl alcohols, although in different relative amounts. Pinoresinol and some higher molecular weight esters of cinnamic and benzoic acids were also found. The structure of these compounds was verified by high performance liquid chromatography–continuous flow fast atom bombardment mass spectrometry. For quantitation, gas chromatography with flame ionization detection was performed. Molecular response factors of the identified compounds were calculated as correction factors of the peak areas. © 1997 by John Wiley & Sons, Ltd.

Suberin from extractive-free cork from Quercus suber L. was depolymerised by methanolysis using different sodium methanolate (NaOMe) concentrations. 1 % and 3 % NaOMe completely removed suberin from cork (54 %-56 % of extractive-free cork), but for lower concentrations there was incomplete solubilisation; with 0.05 % NaOMe, only approximately 80 % of total suberin was removed. The monomeric composition of the extracts differed significantly: for the 0.05 % NaOMe, only alkanoic acids and diacids were found; the yield of v-hydroxy acids increased with reactant concentration, as well as alkanols and ferulic acid.Results from light scattering, SEC and MALDI-MS showed that soluble oligomeric fragments containing suberinic acids were present in the methanolysis mixture. The molecular weight of these oligomeric fragments decreased with higher sodium methanolate concentrations. Keywords Suberin fragmentation CorkQuercus suber L. SEC MALDI-MS MethanolysisBrought to you by | University of Queensland -UQ Library Authenticated Download Date | 6/18/15 12:09 PM