Phosphinecarboxamide based InZnP QDs – an air tolerant route to luminescent III–V semiconductors

We describe a new synthetic methodology for the preparation of high quality, emission tuneable InP-based quantum dots (QDs) using a solid, air- and moisture-tolerant primary phosphine as a group-V precursor. This presents a significantly simpler synthetic pathway compared to the state-of-the-art precursors currently employed in phosphide quantum dot synthesis which are volatile, dangerous and air-sensitive, e.g. P(Si(CH3)3)3

Identification of dissolved organic matter size components in freshwater and marine environments

Dissolved organic matter (DOM) in the transition zone from freshwater to marine systems was analyzed with a new approach for parameterizing the size distribution of organic compounds. We used size-exclusion chromatography for molecular size analysis and quantified colored DOM (CDOM) on samples from two coastal environments in the Baltic Sea (Roskilde Fjord, Denmark and Gulf of Gdansk, Poland). We applied a Gaussian decomposition method to identify peaks from the chromatograms, providing information beyond bulk size properties. This approach complements methods where DOM is separated into size classes with pre-defined filtering cutoffs, or methods where chromatograms are used only to infer average molecular weight. With this decomposition method, we extracted between three and five peaks from each chromatogram and clustered these into three size groups. To test the applicability of our method, we linked our decomposed peaks with salinity, a major environmental driver in the freshwater-marine continuum. Our results show that when moving from freshwater to low-salinity coastal waters, the observed steep decrease of apparent molecular weight is mostly due to loss of the high-molecular-weight fraction (HMW; >2 kDa) of CDOM. Furthermore, most of the CDOM absorbance in freshwater originates from HMW DOM, whereas the absorbing moieties are more equally distributed along the smaller size range (<2 kDa) in marine samples.Peer reviewe

Introduction to modern liquid chromatography

xix+863hlm.;23c

High pH mobile phase effects on silica-based reversed-phase high-performance liquid chromatographic columns

Aqueous mobile phases above pH 8 often cause premature column failure, limiting the utility of silica-based columns for applications requiring high pH. Previous studies suggest that covalently bound silane ligands are hydrolyzed and removed by high-pH mobile phases. However, we found that the siloxane bonds for certain monomeric silanes are hydrolyzed very slowly from silica supports at pH 9–10. Therefore, bonded-phase packing degradation at high pH is a result mainly of silica support dissolution. The rate of column degradation for C18 columns is influenced not only by the type and purity of silica support, but also by the nature of the silane stationary phase. We found different rates of degradation for several commercial C18 columns. The relative rates of silica dissolution for these packings were determined by chemically measuring the silicate formed during column purging at high pH. The type and concentration of mobile phase organic modifier also significantly influences column degradation at high pH. Certain silica-based C18 packings can be used for long periods at pH 9 without significant changes in chromatographic properties. Results of this study better define the practical utility and limitations of silica-based columns in high pH environments

High pH mobile phase effects on silica-based reversed-phase high-performance liquid chromatographic columns

Aqueous mobile phases above pH 8 often cause premature column failure, limiting the utility of silica-based columns for applications requiring high pH. Previous studies suggest that covalently bound silane ligands are hydrolyzed and removed by high-pH mobile phases. However, we found that the siloxane bonds for certain monomeric silanes are hydrolyzed very slowly from silica supports at pH 9–10. Therefore, bonded-phase packing degradation at high pH is a result mainly of silica support dissolution. The rate of column degradation for C18 columns is influenced not only by the type and purity of silica support, but also by the nature of the silane stationary phase. We found different rates of degradation for several commercial C18 columns. The relative rates of silica dissolution for these packings were determined by chemically measuring the silicate formed during column purging at high pH. The type and concentration of mobile phase organic modifier also significantly influences column degradation at high pH. Certain silica-based C18 packings can be used for long periods at pH 9 without significant changes in chromatographic properties. Results of this study better define the practical utility and limitations of silica-based columns in high pH environments

Effect of buffers on silica-based column stability in reversed-phase high-performance liquid chromatography

Previous studies have shown that bonded-phase packing degradation at pH 9–10 mainly is due to silica support dissolution, and does not primarily result from the hydrolysis of covalently attaching siloxane bonds. Column stability also is significantly affected by the type and concentration of organic mobile-phase modifier. We now find that silica-based bonded-phase packings variably degrade with buffers containing different anions and cations. This effect is especially apparent with intermediate- and high-pH buffers. Under the same conditions, pH 10 aqueous carbonate and phosphate buffers with 50% methanol degraded bonded-phase packings much faster than borate and glycine buffers. The nature of the buffer cation also influences bonded-phase packing stability, with column lifetime a function of sodium> potassium> ammonium cations. The rate of bonded-phase packing degradation at pH 7–10 increases with higher concentrations of certain buffers, but especially phosphate. Column degradation is very strongly influenced by temperature. Certain mobile phase-buffer conditions can lead to increased column lifetime, so that practical operation up to pH 10 appears possible for some silica-based columns