Evaluation of selected‐ion flow‐tube mass spectrometry for the measurement of ethanol,methanol and isopropanol in physiological fluids: effect of osmolality and sample volume

Selected‐ion flow‐tube mass spectrometry (SIFT‐MS) is particularly suited for the analysis of volatile low molecular weight compounds. We have evaluated this technique for the assay of different alcohols in aqueous solutions, including blood plasma, and in particular whether the osmolality or sample volume affected vapourisation. Solutions of three different alcohols (methanol, ethanol and isopropanol) ranging from 0.005 to 50 mmol/L were prepared in deionised water (0 milliosmol), phosphate‐buffered saline (690 mOsm), isotonic saline (294 mOsm) and plasma (296 mOsm). The vapour above the sample (50 to 1000 µL) contained in air‐tight tubes at 37°C was aspirated into the instrument. The outputs for ethanol, methanol and isopropanol were linear over the concentration range and independent of the sample volume and relatively independent of the osmolar concentration. SIFT‐MS can reliably and accurately measure common alcohols in the headspace above aqueous solutions, including serum/plasma. This novel application of SIFT‐MS is easy to follow, requires no sample preparation and the wide dynamic range will facilitate measurement of alcohols present from normal metabolism as well as when taken in excess or in accidental poisoning. Copyright © 2009 John Wiley & Sons, Ltd.     

Ionic strength and solvent control over the physical structure, electronic properties and superquenching of conjugated polyelectrolytes

In this paper, we investigate the photophysical properties of the conjugated poly electrolyte poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene) (MPS-PPV), dissolved in both water and DMSO as a function of the solution ionic strength. Dynamic light scattering indicates that MPS-PPV chains exist in a highly agglomerated conformation in both solvents, and that the size of the agglomerates depends on both the ionic strength and the charge of the counter-ion. Even though the degree of agglomeration is similar in the two solvents, we find that the fluorescence quantum yield of MPS-PPV in DMSO is nearly 100-times greater than that in water. Moreover, intensity-dependent femtosecond pump-probe experiments show that there is a significant degree of exciton-exciton annihilation in water but not in DMSO, suggesting that the MPS-PPV chromophores interact to form interchain electronic species that quench the emission in water. Given that the emission quenching properties depend sensitively on the chain conformation and degree of chromophore contact, we also explore the superquenching may be either enhanced or diminished in either of the solvents via addition of simple salts, and we present a molecular picture to rationalize how the conformational properties of conjugated polyelectrolytes can be tuned to enhance their emissive behavior for sensing applications.     

Quantitative XPS imaging—new possibilities with the delay-line detector

X-ray photoelectron spectroscopy (XPS, ESCA) is an ideal tool for identifying differences in surface chemistry. In the past, it has lacked the spatial resolution as well as the performance of elemental or even chemical state imaging, to be of significant use in detecting most microscopic surface phenomena. The recent development of improved micro- or small spot-XPS systems with near-micron spatial resolution as well as outstanding chemical state image performance has opened up a significant opportunity to undertake more detailed studies of micro-structured or micro-patterned surfaces or technical samples with locally distributed impurities. The introduction of a new detector type, the delay-line detector (DLD), to XPS-equipments allows for the first time the acquisition of quantifiable XPS images. This study is intended primarily to explore the capabilities of quantitative ESCA-imaging with respect to the possibilities and limits.     

Perceptual segregation and pitch shifts of mistuned components in harmonic complexes and in regular inharmonic complexes.

It is unclear whether the perceptual segregation of a mistuned harmonic from a periodic complex tone depends specifically on harmonic relations between the other components. A procedure used previously for harmonic complexes [W. M. Hartmann et al., J. Acoust. Soc. Am. 88, 1712-1724 (1990)] was adapted and extended to regular inharmonic complexes. On each trial, subjects heard a 12-component complex followed by a pure tone in a continuous loop. In experiment 1, a mistuning of +/- 4% was applied to one of the components 2-11. The complex was either harmonic, frequency shifted, or spectrally stretched. Subjects adjusted the pure tone to match the pitch of the mistuned component. Near matches were taken to indicate segregation, and were almost as frequent in the inharmonic conditions as in the harmonic case. Also, small but consistent mismatches, pitch shifts, were found in all conditions. These were similar in direction and size to earlier findings for harmonic complexes. Using a range of mistunings, experiment 2 showed that the segregation of components from regular inharmonic complexes could be sensitive to mistunings of 1.5% or less. These findings are consistent with the proposal that aspects of spectral regularity other than harmonic relations can also influence auditory grouping.     

The application of a Shapiro reaction — Suzuki coupling sequence to the stereoselective synthesis of E-trisubstituted olefins

A three-component coupling process is described for the rapid, stereoselective synthesis of a wide variety of E-trisubstituted olefins.