Frying of ground beef at 250 degrees C results in the formation of a series of mutagenic heterocyclic amines, possibly as many as 10 distinct compounds. In this study, the mutagens are separated by aqueous/acid extraction from the beef, XAD adsorption, acid/neutral/base-liquid/liquid extraction, preparative reverse phase h.p.l.c., normal phase h.p.l.c., and analytical reverse phase h.p.l.c. Identification is by low and high resolution mass spectrometry, u.v. absorption spectroscopy and nitrite sensitivity assays. More than 30% of the mutagenic material is identified as 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx). The previously described beef mutagen, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) contributes less than 12% of the total mutagenicity at high temperatures (300 degrees C) and less than 4% at lower temperatures. In addition to MeIQx major mutagens are seen with molecular ions at m/z 227 (C12H13N5), 209 (C13H11N3), and 176 (C9H12N4). Two very polar and two non-polar peaks making a relatively minor contribution to the total mutagenicity (less than 16% total) have not yet been identified. Estimates of the mass of these mutagens in the original cooked beef were made from the mass spectral analysis and the mutagenic recoveries. From one kilogram of cooked ground beef, 1.0 micrograms MeIQx, 0.02 micrograms of IQ, and up to 1.5 micrograms of additional mutagens are formed.

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Athabasca bitumen and other denser-than-water reservoir fluids are coproduced with water or are produced using water or steam injection. Organic solvent injection into reservoirs to reduce hydrocarbon resource viscosity and hence improve production rates is envisaged. A consequence of solvent addition is that the density of the resulting hydrocarbon-rich phase can drop below that of the water-rich phase over broad ranges of composition, temperature, and pressure. In this contribution, densities of Athabasca bitumen from 20 to 200 °C at 0.10, 1.12 and 3.29 MPa, Athabasca bitumen + heptane from 10 to 80 °C at 0.10 MPa and 30 to 140 °C at 0.10, 1.11, and 3.29 MPa and Athabasca bitumen + toluene from 10 to 80 °C at 0.10 MPa were measured (using an Anton Paar DMA 5000 and an Anton Paar DMA HP) and compared with those of pure and produced liquid water from 20 to 200 °C at 0.10, 1.12, and 3.29 MPa. Phase order inversion is shown to overlap with envisaged processing conditions for production, transport, and refining of denser-than-water reservoir fluids because only low mass fractions of solvent are required to cause inversion to occur. The phase order inversion envelopes also include compositions that invert twice as a function of temperature, and the upper temperature associated with phase inversion is a function of pressure. Remote from the critical point of added solvents, the phase inversion boundary is shown to be well-approximated by the ideal mixing assumption applied to Athabasca bitumen + solvent pseudobinary mixtures. The impact of solvent critical temperature on the volume of mixing for solvent + oil mixtures is discussed. Phase order inversion is a general and readily computed phenomenon.

When monoclonal antibodies are exposed to an air−water interface, they form aggregates, which negatively impacts their performance. Until now, the detection and characterization of interfacial aggregation have been difficult. Here, we exploit the mechanical response imparted by interfacial adsorption by measuring the interfacial shear rheology of a model antibody, anti-streptavidin immunoglobulin-1 (AS-IgG1), at the air−water interface. Strong viscoelastic layers of AS-IgG1 form when the protein is adsorbed from the bulk solution. Creep experiments correlate the compliance of the interfacial protein layer with the subphase solution pH and bulk concentration. These, along with oscillatory strain amplitude and frequency sweeps, show that the viscoelastic behavior of the adsorbed layers is that of a soft glass with interfacial shear moduli on the order of 10 −3 Pa m. Shifting the creep compliance curves under different applied stresses forms master curves consistent with stress−time superposition of soft interfacial glasses. The interfacial rheology results are discussed in the context of the interface-mediated aggregation of AS-IgG1.