Negative Ion fast atom bombardment (FAB) mass spectra were found to allow the determination of the linkage position and sugar sequences In a series of (underivatized) dlsaccharkles and of linear oligosaccharides. Discrimination of 1-4, 1-6, 1-3, and 1-2 linkage type and determination of the reducing end and of the monosaccharide sequence Is made possible by the analysis of the negative metastable Ions produced In linked scans FAB MS. The peculiarity of negative Ionization Is believed to consist In a selective deprotonatlon of the anomeric hydroxyl (reducing end of the oligosaccharide chain), which Is more acidic with respect to the remaining OH groups. Once the negative charge Is localized at the oligosaccharide reducing end, the Ion fragmentation of this ring occurs rapidly and the mass losses observed are found to be diagnostic of the glycoside linkage type between adjacent sugar units. The overall negative Ions fragmentation process outlined above allows the simultaneous Identification of the reducing end of the chain, of the monosaccharide units sequence, and of the linkage type between adjacent units.

The recent finding that significant information on copolymer microstructure can be obtained by using mass spectrometry has stimulated our work toward developing appropriate algorithms to match the experimental mass spectra to those theoretically calculated. A novel program for the determination of microstructure in copolymers by computer simulation of mass spectra is reported. The statistical model used to describe copolymer distributions is reported in detail in the text. The computer simulation program (MACOS) is discussed, and three illustrative examples are given.

and CONCETTO PUGLISI, DANIELE VITALINI, Istituto per la Chimica e la Tecnologia dei Materiuli Polimerici, Consigh Nazion.uk deUe Ricerche, Viak A. Doria, 6-95125 Cataniu, Italy, and S . CUCINELLA, Enichern SPA.-Sun Donuto Milanese, 20100 Milam, Italy synopsisThe mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol-A carbonate) (PC) has been investigated. These compounds are capable of inducing a self-extinguence in PC even when present in very low amounts (0.2-1%). Thermogravimetric and flash pyrolysis-GC-M!3 data show the thermal degradation rate of PC enhanced, and the distribution of the volatile pyrolysis products was modified by these additives. Oxygen Index (01) and Nitrous Oxide Index (NOI) measurements indicate a FR condensed-phase mechanism of these additives. Traces of polymer surface temperature against time, measured under forced flame conditions, show that the expanded carbon layer formed in the combustion of polycarbonatearomatic d f o n a t e blends produces a heat insulating effect toward the undecomposed bulk. The overall evidence leads us to conclude that aromatic sulfonates cause the flame extinguishment in polycarbonate by an intumescent phenomenon.

SynopsisThe thermal decomposition products that evolve from poly(viny1 chloride) (PVC), poly(viny1 bromide) (PVB), poly(viny1 alcohol) (PVA), and poly(viny1 acetate) (PVAc) were analyzed by direct pyrolysis in the ion source of a mass spectrometer (MS). Our results indicate that in both stages of the decomposition process which occurred in the four vinyl polymers investigated several aromatic hydrocarbons were produced and that the relative amounts of benzene, napthalene, and anthracene were different in the two stages. This previously unreported information determines in a single scheme the thermal behavior of the title compounds.

Sophorose lipids (SLs) have applications as surfactants and are produced at high levels by several yeasts. We developed a fed-batch shake-flask method for the production of SLs by Candida bombicola ATCC 22214. Optimal aeration, expressed in terms of oxygen transfer rate, was between 50 and 80 mM O(2)/L h(-1) and resulted in maximum values for both volumetric product formation (1-1.5 g/L h(-1)) and SL yield (350 g/L). The lowest aeration levels resulted in the enrichment in saturated fatty acid SLs at the expense of unsaturated fatty acid SLs.