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The formation of acrylamide was measured in real time during thermal treatment (120-170 degrees C) of potato as well as in Maillard model systems composed of asparagine and reducing sugars, such as fructose and glucose. This was achieved by on-line monitoring of acrylamide released into the headspace of the samples using proton transfer reaction mass spectrometry (PTR-MS). Unambiguous identification of acrylamide by PTR-MS was accomplished by gas chromatography coupled simultaneously to electron-impact MS and PTR-MS. The PTR-MS ion signal at m/z 72 was shown to be exclusively due to protonated acrylamide obtained without fragmentation. In model Maillard systems, the formation of acrylamide from asparagine was favored with increasing temperature and preferably in the presence of fructose. Maximum signal intensities in the headspace were obtained after approximately 2 min at 170 degrees C, whereas 6-7 min was required at 150 degrees C. Similarly, the level of acrylamide released into the headspace during thermal treatment of potato was positively correlated to temperature.

The goal of this study was to better understand the correspondence between sensory perception and in-nose compound concentration. Five aroma compounds at three different concentrations increasing by factors of 4 were added to four matrixes (water, skim milk, 2.7% fat milk, and 3.8% fat milk). These were evaluated by nosespace analysis with detection by proton transfer reaction mass spectrometry (PTR-MS), using five panellists. These same panellists evaluated the perceived intensity of each compound in the matrixes at the three concentrations. PTR-MS quantification found that the percent released from an aqueous solution swallowed immediately was between 0.1 and 0.6%, depending on the compound. The nosespace and sensory results showed the expected effect of fat on release, where lipophilic compounds showed reductions in release as fat content increases. The effect is less than that observed in headspace studies. A general correlation between nosespace concentration and sensory intensity ratings was found. However, examples of perceptual masking were found where higher fat milks showed reductions in aroma compound intensity ratings, even if the nosespace concentrations were the same.

An experimental technique is investigated to separate/enrich fullerenes of metallofullerenes, exploiting differences in sublimation temperatures without the use of solvents. Fullerenes are sublimed out of the soot and deposited on a quartz rod along a temperature gradient (gradient sublimation). In a position-sensitive experiment the composition of the deposit on the rod is monitored by laser-desorption mass spectrometry. Strongly enriched regions containing specific fullerene molecules (i.e., C[sub 84] or LaC[sub 82]) are observed. Furthermore, C[sub 74], which could not be extracted from the soot by organic solvents, sublimes out of the soot. 26 refs., 6 figs.

Surface collisions of negatively charged atomic clusters C N - and Si N - , N

The authors report the formation of fullerenes from graphite by sputtering and electron beam evaporation. Under conditions that differ dramatically from those in the previously known fullerene production processes, the new methods preferentially yield the soluble higher fullerenes C{sub 70}, C{sub 76}, C{sub 78}, and C{sub 84} in addition to minor amounts of C{sub 60} only. Upon passage of carbon particles formed by electron beam evaporation through an electrostatic field, fullerenes are mainly isolated from the cathode, not from the anode, which supports the formation of cationic intermediates in fullerene growth mechanisms. The variables thought to be important for fullerene production can be controlled efficiently in the new processes. 18 refs., 3 figs.

The technique of carbon-arc evaporation has been successfully utilized to encapsulate a wide variety of rare-earth species in carbon cages. The authors have observed M{sub m} @ C{sub n} (M = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, or Er) species present in the toluene extracts of the carbon soot using laser desorption mass spectrometry. The presence of multiple-metal species appears to depend strongly on the metal-to-carbon atom ratio found in the starting rods, with the higher metal concentrations favoring multiple-metal incorporation. One often observed dimetallofullerene is M{sub 2}{degrees}C{sub 80}. Molecular orbital arguments are presented to support a possible icosahedral structure for C{sub 80}. 27 refs., 2 figs., 1 tab.