Hyperbranched polyesteramides (DA2), prepared from hexahydrophthalic anhydride (D) and diisopropanolamine (A) have been characterized, by use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), field desorption (FD)-MS, and electrospray ionization (ESI)-MS. MALDI of polyesteramides produces protonated molecules. The spectra show a complex chemical composition distribution and end-group distribution which are mainly composed of two series of homologous oligomers DnA(n)+1 - mH2O and DnA(n) - mH2O, where m = 1-2. Signals from protonated molecules DnAn+1 and DnAn are almost absent in the MALDI spectrum, whereas these ions are responsible for the base peak of DnA(n)+1 - mH2O and DnA(n) - mH2O (m = 1-2) clusters in the ESI spectrum. The absence of -OH end-groups signals in the MALDI spectrum is due to a metastable decay of protonated DnA(n)+1 and DnAn ions in the ion source of the MALDI mass spectrometer prior to ion extraction. In-source decay results in the formation of protonated lower DnA(n)+1 - mH2O and DnA(n) - mH2O oligomers and their corresponding neutrals, leading to wrong conclusions concerning the relative end-group distribution as a function of the degree of polymerization and the chemical composition.
The molybdenum nitrido complex 15NMo[N(R)Ar]3 (where R = C(CD3)2CH3, Ar = 3,5-C6H3Me2) reacted with the anhydride of trifluoroacetic acid at room temperature to afford the correspondent organonitrogen compound in almost quantitative yield without the necessity of using additional reagents to achieve the C-N coupling.
Two organic fouling samples obtained from downstream the cracking oven (DS) and from upstream the hot zone (US) of a steam cracker facility were characterized. For this purpose, a simultaneous thermal analyzer coupled to a photoionization mass spectrometer (STA-PI-MS) and a thermal desorption/pyrolysis gas chromatograph (TD/Py-GC-EI-MS) were used. Mass loss and differential scanning calorimetry information revealed the degradation of the materials beginning at 130 °C with two distinct maxima for US and one for DS (230−330 °C) as well as broad signals (330−500 °C) for both. Structural motives of different polymeric-like structures were assigned based on PI-MS of the effluent and separately conducted TD/Py-GC-EI-MS. The advantage of soft photoionization over hard ionization techniques such as electron ionization is the considerable reduction of fragmentation, yielding higher abundancies of molecular ions. Thus, even though complex samples are studied, evolving constituents can often be easily tracked in a time-resolved manner (1 Hz). While single photon ionization (SPI, 118 nm = 10.5 eV) ionizes most organic molecules, resonance-enhanced multiphoton ionization (REMPI, 2 × 266 nm = 9.4 eV) selectively addresses aromatic species. Differentiation of polymeric-like structures was achieved by exploiting this selectivity (SPI vs REMPI) and comparison of molecular patterns with GC-EI-MS data, which supports the identification of compounds by providing fragmentation patterns and chemical information based on retention time. US shows high inorganic content (∼50%) and more diversity in its organic part, as indicated by four types of patterns: polyethylene-like, Diels−Alderlike, polythioether/polysulfide-like, and polystyrene-like motives. In contrast, DS exhibits almost only signals of Diels−Alderlike and polystyrene-like structures and contains a less inorganic material (∼23%). Additionally, first attempts to quantify the Diels−Alder content by STA-SPI-MS were successfully conducted.
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