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Protonation-Independent Charge Transport Across Diphenylamine Single-Molecule Junctions.
J Phys Chem Lett
January 2025
Department of Physics, City University of Hong Kong, Kowloon 999077, Hong Kong, China.
Amines are one of the most ubiquitous functional groups in molecular junctions; however, the exact regulation of the charge transport through the protonation state of an amine group in the junction backbone remains elusive. We address this question here by designing a diphenylamine molecular backbone and experimentally investigating how protonation of the central amine group affects the charge transport. Our ultraviolet-visible spectroscopy measurements demonstrate the protonation reaction of the diphenylamine compound in the presence of either trifluoroacetic acid or HCl, and we observe a consistent trend of a modestly increased conductance for diphenylamine in the presence of acid, indicating that a protonated amine group in a diphenylamine backbone slightly enhances the electron conduction.
View Article and Find Full Text PDFHydrolysis Reactions of p-Nitrophenyl Trifluoroacetate and S-Ethyl Trifluorothioacetate.
Molecules
January 2025
Department of Chemistry and Biochemistry, University of North Florida, Jacksonville, FL 32224, USA.
The formation of water structures can provide significant benefits in organic reactions, stabilizing charge and lowering activation energies. Hydrolysis reactions will frequently rely on water networks to accomplish these goals. Here, we used computational chemistry and experimental kinetics to investigate a model thioester molecule S-ethyl trifluorothioacetate, and extended work on a previously characterized ester p-nitrophenyl trifluoroacetate.
View Article and Find Full Text PDFA Cost-Effective Nonaqueous Reversed-Phase High-Performance Liquid Chromatography Method to Measure Vitamin D3 in Hen's Egg Yolk.
J Sep Sci
January 2025
Department of Pharmaceutical Sciences, University of Perugia, Perugia, Italy.
The objective of this study is to develop an HPLC-UV method for the cost-effective and quantitative determination of vitamin D3 in food, even in the presence of vitamin D2, with a specific focus on egg yolk. During method development, the performance of three stationary phases in resolving the peak of vitamin D2 from that of vitamin D3 was investigated. The physicochemical properties of these phases differed particularly in the extent of hydrophobicity and silanophilic activity, including a GraceSmart RP C18 column without silanol endcapping, a Robusta RP C18 column with silanol endcapping, and a Waters Xbridge RP C18 column with ethylene-bridged hybrid (BEH) particle technology.
View Article and Find Full Text PDFRP-HPLC Method for Rhein Quantification in L. (Fabaceae) Leaves.
Acta Med Philipp
December 2024
Institute of Herbal Medicine, National Institutes of Health, University of the Philippines Manila.
Objectives: The aim of this study is to establish a Reversed Phase - High Performance Liquid Chromatographic (RP-HPLC) method for the quantification of Rhein from L. leaves.
Methods: A Shimadzu system equipped with a C18 Column (150 x 4.
A new stability indicating HPLC method with QDa and PDA detectors for the determination of process and degradation impurities of ivabradine including separation of diastereomeric -oxides.
Anal Methods
January 2025
Istanbul University, Faculty of Pharmacy, Department of Analytical Chemistry, 34116, Istanbul, Turkey.
In this study, a new reversed phase high performance liquid chromatography method using two detectors was developed for the analysis of degradation and process impurities of ivabradine in pharmaceutical preparations. A PDA detector set to 285 nm wavelength and a QDa detector set to positive scan mode were used in the method. In the developed method, the separation process was carried out in a Zorbax phenyl column with a gradient application of a 0.
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