scholarly journals Determination of χ from liquid-liquid phase data in ternary polymer systems (solvent/polymer/polymer) with hydrogen bonding

2008 ◽  
Vol 2 (5) ◽  
pp. 313-329 ◽  
Author(s):  
J. E. Figueruelo ◽  
R. Garcia-Lopera ◽  
I. S. Monzo ◽  
C. Abad ◽  
A. Campos
Keyword(s):  
Hydrogen Bonding ◽  
Liquid Phase ◽  
Polymer Systems ◽  
Phase Data ◽  
Ternary Polymer

Hydrogen bonding in ternary polymer blend systems: determination of association parameters

1992 ◽  
Vol 25 (26) ◽  
pp. 7101-7106 ◽  
Author(s):  
Christophe Le Menestrel ◽  
Dorab E. Bhagwagar ◽  
Paul C. Painter ◽  
Michael M. Coleman ◽  
John F. Graf
Keyword(s):  
Hydrogen Bonding ◽  
Polymer Blend ◽  
Ternary Polymer

The Well Stirred Liquid Phase Photochemical Reactor: Laboratory Tool or Master of Disguises?

2016 ◽  
Vol 19 (2) ◽  
Author(s):  
David Ollis
Keyword(s):  
Steady State ◽  
Liquid Phase ◽  
Rate Constants ◽  
Light Flux ◽  
Kinetic Studies ◽  
Prior Work ◽  
True Rate ◽  
Phase Data ◽  
Laboratory Tool

AbstractSince the early 1980s, liquid phase kinetic studies of homogeneous and heterogeneous photochemistry (especially including photocatalysis), have routinely utilized well stirred laboratory scale photoreactors. Convenient as these reactors are, their operation may be limited by reactant concentration, or by a transport limitation for light flux or dissolved oxygen. Similarly, the mechanistic interpretation of most phootocatalyzed liquid phase data has assumed the validity of Langmuir-Hinshelwood kinetics, whereas recent papers have demonstrated decisively that a pseudo steady state prevails, rather than equilibrium adsorption circumstance. We briefly review these circumstances which have led to kinetic disguises, and offer simple recommendations for future homogeneous and heterogeneous photochemical liquid phase studies which will allow determination of true rate constants and avoid the transport phenomena and mechanistic disguises evident in prior work.

Multi-walled Carbon Nanotubes Reinforced into Hollow Fiber by Chitosan Sol-gel for Solid/Liquid Phase Microextraction of NSAIDs from Urine Prior to HPLC-DAD Analysis

2019 ◽  
Vol 20 (5) ◽  
pp. 390-400 ◽  
Author(s):  
Nabil N. AL-Hashimi ◽  
Amjad H. El-Sheikh ◽  
Rania F. Qawariq ◽  
Majed H. Shtaiwi ◽  
Rowan AlEjielat
Keyword(s):  
Carbon Nanotubes ◽  
Liquid Phase ◽  
Hollow Fiber ◽  
Sol Gel ◽  
Liquid Phase Microextraction ◽  
Extraction Device ◽  
Multi Walled Carbon Nanotubes ◽  
Solid Liquid ◽  
Walled Carbon Nanotubes

Background: The efficient analytical method for the analysis of nonsteroidal antiinflammatory drugs (NSAIDs) in a biological fluid is important for determining the toxicological aspects of such long-term used therapies. Methods: In the present work, multi-walled carbon nanotubes reinforced into a hollow fiber by chitosan sol-gel assisted-solid/ liquid phase microextraction (MWCNTs-HF-CA-SPME) method followed by the high-performance liquid chromatography-diode array detection (HPLC–DAD) was developed for the determination of three NSAIDs, ketoprofen, diclofenac, and ibuprofen in human urine samples. MWCNTs with various dimensions were characterized by various analytical techniques. The extraction device was prepared by immobilizing the MWCNTs in the pores of 2.5 cm microtube via chitosan sol-gel assisted technology while the lumen of the microtube was filled with few microliters of 1-octanol with two ends sealed. The extraction device was operated by direct immersion in the sample solution. Results: The main factors influencing the extraction efficiency of the selected NSAIDs have been examined. The method showed good linearity R2 ≥ 0.997 with RSDs from 1.1 to 12.3%. The limits of detection (LODs) were 2.633, 2.035 and 2.386 µg L-1, for ketoprofen, diclofenac, and ibuprofen, respectively. The developed method demonstrated a satisfactory result for the determination of selected drugs in patient urine samples and comparable results against reference methods. Conclusion: The method is simple, sensitive and can be considered as an alternative for clinical laboratory analysis of selected drugs.

Determination of estrogens in wastewater using three-phase hollow fiber-mediated liquid-phase microextraction followed by HPLC

2008 ◽  
Vol 31 (4) ◽  
pp. 622-628 ◽  
Author(s):  
Meihua Liu ◽  
Bin Qiu ◽  
Xia Jin ◽  
Lan Zhang ◽  
Xi Chen ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Hollow Fiber ◽  
Liquid Phase Microextraction ◽  
Three Phase

scholarly journals Deciphering the Role of π-Interactions in Polyelectrolyte Complexes Using Rationally Designed Peptides

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2074
Author(s):  
Sara Tabandeh ◽  
Cristina Elisabeth Lemus ◽  
Lorraine Leon
Keyword(s):  
Hydrogen Bonding ◽  
Phase Separation ◽  
Liquid Phase ◽  
Charge Density ◽  
Secondary Structures ◽  
Liquid Phase Separation ◽  
Polyelectrolyte Complexes ◽  
Π Interactions ◽  
Liquid Liquid Phase Separation

Electrostatic interactions, and specifically π-interactions play a significant role in the liquid-liquid phase separation of proteins and formation of membraneless organelles/or biological condensates. Sequence patterning of peptides allows creating protein-like structures and controlling the chemistry and interactions of the mimetic molecules. A library of oppositely charged polypeptides was designed and synthesized to investigate the role of π-interactions on phase separation and secondary structures of polyelectrolyte complexes. Phenylalanine was chosen as the π-containing residue and was used together with lysine or glutamic acid in the design of positively or negatively charged sequences. The effect of charge density and also the substitution of fluorine on the phenylalanine ring, known to disrupt π-interactions, were investigated. Characterization analysis using MALDI-TOF mass spectroscopy, H NMR, and circular dichroism (CD) confirmed the molecular structure and chiral pattern of peptide sequences. Despite an alternating sequence of chirality previously shown to promote liquid-liquid phase separation, complexes appeared as solid precipitates, suggesting strong interactions between the sequence pairs. The secondary structures of sequence pairs showed the formation of hydrogen-bonded structures with a β-sheet signal in FTIR spectroscopy. The presence of fluorine decreased hydrogen bonding due to its inhibitory effect on π-interactions. π-interactions resulted in enhanced stability of complexes against salt, and higher critical salt concentrations for complexes with more π-containing amino acids. Furthermore, UV-vis spectroscopy showed that sequences containing π-interactions and increased charge density encapsulated a small charged molecule with π-bonds with high efficiency. These findings highlight the interplay between ionic, hydrophobic, hydrogen bonding, and π-interactions in polyelectrolyte complex formation and enhance our understanding of phase separation phenomena in protein-like structures.

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