Analysis of biodiesel/petroleum diesel blends with comprehensive two-dimensional gas chromatography

Comprehensive two-dimensional gas chromatography (GCxGC) is used to analyze petroleum diesel, biodiesel, and biodiesel/petroleum diesel blends. The GCxGC instrument is assembled from a conventional gas chromatograph fitted with a simple, in-line fluidic modulator. A 5% phenyl polydimethylsiloxane primary column is coupled to a polyethylene glycol secondary column. This column combination generates chromatograms where the fatty acid methyl esters (FAMEs) found in biodiesel occupy a region that is also populated by numerous cyclic alkanes and monoaromatics found in petroleum. Fortunately, the intensities of the petroleum hydrocarbon peaks are far lower than the intensities of the FAME peaks, even for blends with low biodiesel content. This allows the FAMEs to be accurately quantitated by direct integration. The method is calibrated by analyzing standard mixtures of soybean biodiesel in petroleum diesel with concentrations ranging from 1 to 20% v/v. The resulting calibration curve displays excellent linearity. This curve is used to determine the concentration of a B20 biodiesel/petroleum diesel blend obtained from a local retailer. Excellent precision and accuracy are obtained.     

Transfer measurements for the Ti+Ni systems at near barrier energies

Large enhancements have been observed in the sub-barrier fusion cross sections for Ti+Ni systems in our previous studies. Coupled channel calculations incorporating couplings to 2⁺ and 3⁻ states failed to explain these enhancements completely. A possibilty of transfer channels contributing to the residual enhancements had been suggested. In order to investigate the role of relevant transfer channels, measurements of one- and two-nucleon transfer were carried out for ^46,48Ti+⁶¹Ni systems. The present paper gives the results of these studies.     

Glycoproteomics: Charting new territory in mass spectrometry and glycobiology

Glycosylation is an incredibly common and diverse post-translational modification that contributes widely to cellular health and disease. Mass spectrometry is the premier technique to study glycoproteins; however, glycoproteomics has lagged behind traditional proteomics due to the challenges associated with studying glycosylation. For instance, glycans dissociate by collision-based fragmentation, thus necessitating electron-based fragmentation for site-localization. The vast glycan heterogeneity leads to lower overall abundance of each glycopeptide, and often, ion suppression is observed. One of the biggest issues facing glycoproteomics is the lack of reliable software for analysis, which necessitates manual validation and serves as a massive bottleneck in data processing. Here, I will discuss each of these challenges and some ways in which the field is attempting to address them, along with perspectives on how I believe we should move forward.     

Formation of high-capacity protein-adsorbing membranes through simple adsorption of poly(acrylic acid)-containing films at low pH

Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3-6-fold. The low adsorption pH generates a high density of -COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, membranes containing PAA/polyethylenimine (PEI)/PAA films bind 93 mg of histidine(6)-tagged (His-tagged) ubiquitin per cm(3) of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2-3-fold higher than for commercially available immobilized metal affinity chromatography (IMAC) resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low-pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~40 mg/cm(3). Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH).     

Limitations of the scalp-hair biologic monitor in assessing selenium status in epidemiological investigations

Scalp hair is routinely used to assess exposure to toxic trace elements and nutritional status of some required trace elements. The advantages and disadvantages of hair as a biologic monitor have been comprehensively discussed in the literature for many years. Among the concerns is distinguishing between exogenous and endogenous contributions. Nested in this issue is the longitudinal distribution of a trace element along the hair strand. The typical observation for many elements of interest is that the element concentration increases from the root end to the distal end; and this is attributed to continuing contamination from exogenous sources. In this study we used neutron activation analysis to measure 14 trace elements in 6 mm segments of full-length scalp hair from three healthy members of the same household having light-urban environmental exposure. To extend the data set for selenium, we included three adult female subjects with longer than average scalp hair. From these trace-element concentrations we calculated the root-to-distal end ratios as a profile diagnostic of trace-element distributions. Ratios fall into three diagnostic categories, >1, ≈1, and <1 corresponding to profiles having decreasing root-to-distal concentrations, unchanging concentrations, and increasing concentrations, respectively. Of the 14 elements measured, only Se has R > 1, Zn and S have R ≈ 1, and the remaining 11 elements all have R < 1 in the order: As > I > Hg ≈ Au ≈ Mg ≈ Mn ≈ Sb ≈ Ca > Cu > Al ≈ Ag. R _Se is greater than 1 and increases with hair length (P = 0.02) corresponding to a continuous longitudinal loss of Se in stark and puzzling contrast to the other elements measured. An analogous loss of Se in the nail monitor was not observed leading us to conclude that the nail is less prone to misclassification of selenium status in epidemiological studies.     

T3P-promoted synthesis of a series of novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones

A series of 11 novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-aryl-C-phenyl imines with thiosalicylic acid. This provides simple and ready access to N-aryl compounds in this family, which have been generally difficult to prepare.     

The electrodeposition of high-density,ordered arrays of Bi1-xSbx nanowires

Here we report the synthesis of dense arrays of Bi1-xSbx nanowires with >5 x 1010 nanowires/cm2. The individual wires are crystalline, relatively homogeneous, and highly textured in a 110 direction, with diameters of 40 nm and a composition of x = 12-15 atom % Sb. By tuning the solution concentrations and controlling the growth rate by controlling the potential, the composition, crystallinity, and morphology of the nanowires can be varied.     

Surface enhanced raman and resonance raman spectroscopy in a non-aqueous electrochemical environment: Tris(2,2′-bipyridine)ruthenium(II) adsorbed on silver from acetonitrile

This letter reports the first observation of both surface enhanced Raman scattering (SERS) and surface enhanced resonance Raman scattering (SERRS) from the transition metal complex tris(2,2′-bipyridine)ruthenium (II), Ru(bpy)₃²⁺, adsorbed on a silver electrode from acetonitrile (ACN). The assignment of these spectra as valid examples of SERS and SERRS in a non-aqueous environment is based on the following criteria: (1) in situ demonstration of monolayer surface coverage of Ru(bpy)₃²⁺ using double potential step chronocoulometry (DPSCC); (2) the Raman signals are most intense after surface roughening by anodization; (3) the Raman spectra are potential dependent in the non-faradaic potential region; (4) the measured enhancement factors are greater ilian 10⁶; (5) the surface spectra are frequency shifted relative to their bulk counterpart; and (6) several other molecules also exhibit non-aqueous SERS and SERRS behavior. These results are highly significant in that generality of surface enhanced Raman spectroscopy has been extended into the rich domain of nonaqueous electrochemistry.