3 research outputs found
Resource management for multimedia traffic over ATM broadband satellite networks
No full textPhDAbstract not availabl
Effect of Mobile Phase pH on the Electrospray Ionization Efficiency and Qualitative Analysis of Pharmaceuticals in ESI + LC-MS/MS
No full textThe effect of mobile phase pH on positive ionization process and retention time of nine pharmaceuticals on ultra-performance liquid chromatography-electrospray-tandem mass spectrometry (LC-MS/MS) was discussed. The effective use of high and low mobile phase pH in LC-MS/MS qualitative analyses method was also evaluated by comparing the instrument detection limit, quantification limit, precision, linearity and signal to noise (S/N) under low and high mobile phase pH. In this work, six mobile phase pH that ranged between pH 2 and pH 10 were used to evaluate the effect of the mobile phase pH changes on the ionization process in electrospray ionization. Results revealed that high mobile phase pH ionized more pharmaceuticals molecules and gave a higher signal than low mobile phase pH in positive ionization mode. The results proved that ammonium ion was better as a proton donor in high pH mobile phase than the hydronium ion in acidic mobile phase. The results revealed that the qualitative LC-MS/MS analyses method by using high mobile phase pH has better performance for most analytes in terms of sensitivity, precision, linearity and S/N than the low mobile phase pH. © 2019 The Author(s). Published by Oxford University Press. All rights reserved
Correlation of metal anode reversibility with solvation chemistry and interfacial electron transfer in aqueous electrolytes.
No full textReversible electrodeposition of metals is a crucial route to developing high-energy and rechargeable batteries. However, uncontrolled and nonplanar morphological evolution and parasitic reactions at the metal anodes are fundamental barriers to realizing full reversibility. Here, using aqueous electrochemistry as a probe, we develop multiscale characterization tools that can precisely determine the root cause of these morphological instabilities and parasitic reactions. Our analysis indicates that these issues are fundamentally from the free water molecules in aqueous electrolytes, leading to low reversibility of metal anodes. We therefore demonstrate a straightforward and effective strategy, based on modulating the solute anions in aqueous electrolytes, to suppress free water molecule concentration in conventional aqueous electrolytes. A proof of concept is demonstrated using a Zn metal anode, which shows unprecedented reversibility and stability in conventional aqueous electrolytes with structure-making anions under a harsh condition of 10 milliampere hours per square centimeter. This work unlocks an alternative angle to develop sustainable electrolytes for cost-efficient, practical battery chemistries.Funding: Research conducted in this study is funded by the King Abdullah University ofScience and technology (KAUSt). Author contributions: Y.Z. and h.n.A. conceived theproject. Y.Z. designed the experiments and conducted electrochemical tests and spectroscopicexperiments. S.t. performed theoretical simulations. t.W. fitted the tafel plots. Y.Z. andX.G. conducted operando nMR tests. Y.W. and c.l. performed electron microscopy. Y.Z. wrotethe manuscript with input from all authors. All authors approved the final version of thismanuscript. Competing interests: the authors declare that they have no competing interests
