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Hybrid materials, integrating the merits of individual components, are ideal structures for efficient oxygen evolution reaction (OER). However, the rational construction of hybrid structures with decent physical/electrochemical properties is yet challenging. Herein, a promising OER electrocatalyst composed of trimetallic metal-organic frameworks supported over S/N-doped carbon macroporous fibers (S/N-CMF@Fe x Co y Ni 1-x-y -MOF) via a cation-exchange strategy is delicately fabricated. Benefiting from the trimetallic composition with improved intrinsic activity, hollow S/N-CMF matrix facilitating exposure of active sites, as well as their robust integration, the resultant S/N-CMF@Fe x Co y Ni 1-x-y -MOF electrocatalyst delivers outstanding activity and stability for alkaline OER. Specifically, it needs an overpotential of 296 mV to reach the benchmark current density of 10 mA cm -2 with a small Tafel slope of 53.5 mV dec -1 . In combination with X-ray absorption fine structure spectroscopy and density functional theory calculations, the post-formed Fe/Co-doped γ-NiOOH during the OER operation is revealed to account for the high OER performance of S/N-CMF@Fe x Co y Ni 1-x-y -MOF., (© 2023 Wiley-VCH GmbH.)

All-inorganic cesium lead triiodide (CsPbI 3 ) perovskite has received increasing attention due to its intrinsic thermal stability and suitable band gap for photovoltaic applications. However, it is difficult to deposit high-quality pure-phase CsPbI 3 films using CsI and PbI 2 as precursors due to the rapid nucleation and crystal growth by the solution coating method. Here, a simple cation-exchange approach is employed to fabricate all-inorganic 3D CsPbI 3 perovskite, where 1D ethylammonium lead (EAPbI 3 ) perovskite is first solution-deposited and then transformed to 3D CsPbI 3 via ion exchange between EA + and Cs + during thermal annealing. The large space between the PbI 3 - skeletons in 1D EAPbI 3 favors the cation interdiffusion and exchange for the formation of pure-phase 3D CsPbI 3 with full compactness and high crystallinity and orientation. The resulting CsPbI 3 film exhibits a low trap density of state and high charge mobility, and the perovskite solar cell shows a power-conversion efficiency of 18.2% with enhanced stability. This strategy provides an alternative and promising fabrication route for the fabrication of high-quality all-inorganic perovskite devices.

Ion-exchange chromatography (IEC) is a fractionation technique that allows for the separation of ionizable molecules on the basis of differences in their electrostatic properties. Its large sample-handling capacity, broad applicability (particularly to proteins and enzymes), moderate cost, powerful resolving ability, ability to perform simultaneous quantitation, and ease of scale-up and automation have led to it becoming one of the most versatile and widely used of all liquid chromatography (LC) techniques. In this chapter, we review the basic principles of IEC, as well as the broader criteria for selecting IEC conditions. By way of further illustration, we outline basic laboratory protocols to partially purify a soluble serine peptidase from bovine whole brain tissue, covering crude tissue extract preparation through to partial purification of the target enzyme using a form of IEC, namely, anion-exchange chromatography. Protocols for assaying total protein and enzyme activity in both pre- and post-IEC fractions are also described., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Well dispersible and stable single atom catalysts (SACs) with hydrophilic features are highly desirable for selective hydrogenation reactions in hydrophilic solvents towards important chemicals and pharmaceutical intermediates. A general strategy is reported for the fabrication of hydrophilic SACs by cation-exchange approach. The cation-exchange between metal ions (M = Ni, Fe, Co, Cu) and Na + ions introduced in the skeleton of metal oxide (TiO 2 or ZrO 2 ) nanoshells plays the key role in forming M 1 /TiO 2 and M 1 /ZrO 2 SACs, which efficiently prevents the aggregation of the exchanged metal ions. The as-obtained SACs are highly dispersible and stable in hydrophilic solvents including alcohol and water, which greatly facilitates the catalysis reaction in alcohol. The Ni 1 /TiO 2 SACs have been successfully utilized as catalysts for the selective C=C hydrogenation of cinnamaldehyde to produce phenylpropanal with 98% conversion, over 90% selectivity, good recyclability, and a turnover frequency (TOF) of 102 h -1 , overwhelming most reported catalysts including noble metal catalysts., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The fractionation of positional isomers of a PEGylated protein is quite challenging as these have similar molecular weight, and only very slightly different surface charge. In this study, cation exchange z 2 laterally-fed membrane chromatography (z 2 LFMC), which has been shown to be suitable for high-speed, high-resolution protein purification, was used to fractionate positional isomers of mono-PEGylated lysozyme. The performance of the z 2 LFMC device was compared with a commercial preparative cation exchange column having the same volume and ligand. PEGylated lysozyme purification experiments showed that while the positional isomers of mono-PEGylated lysozyme could not be satisfactorily resolved using the preparative commercial cation exchange column, almost baseline resolution of these could be achieved using the z 2 LFMC device. Moreover, the z 2 LFMC device-based process was faster by an order of magnitude. The results discussed in this paper demonstrate that z 2 LFMC is a superior alternative to column-based chromatography for challenging protein separations, such as the one discussed here, both in terms of speed and resolution., (Copyright © 2022 Elsevier B.V. All rights reserved.)

There is strong need to reduce the manufacturing costs and increase the downstream purification efficiency of high-value therapeutic monoclonal antibodies (mAbs). This paper explores the performance of a weak cation-exchange membrane based on the coupling of IDA to poly(butylene terephthalate) (PBT) nonwoven fabrics. Uniform and conformal layers of poly(glycidyl methacrylate) (GMA) were first grafted to the surface of the nonwovens. Then IDA was coupled to the polyGMA layers under optimized conditions, resulting in membranes with very high permeability and binding capacity. This resulted in IgG dynamic binding capacities at very short residence times (0.1-2.0 min) that are much higher than those achieved by the best cation-exchange resins. Similar results were obtained in the purification of a single-chain (scFv) antibody fragment. As is customary with membrane systems, the dynamic binding capacities did not change significantly over a wide range of residence times. Finally, the excellent separation efficiency and potential reusability of the membrane were confirmed by five consecutive cycles of mAb capture from its cell culture harvest. The present work provides significant evidence that this weak cation-exchange nonwoven fabric platform might be a suitable alternative to packed resin chromatography for low-cost, higher productivity manufacturing of therapeutic mAbs and antibody fragments.

Mixed-mode cation-exchange stationary phases are useful for the separation of mixtures containing hydrophobic, acidic, and basic molecules. To ensure that weak organic bases are protonated and carboxylic acids are neutral low pH mobile phases are required. Mixed-mode stationary phases that are stable at pH < 3 are needed. We synthesized a crosslinked structure along the surface of thiol functionalized silica gel particles using the thiol-yne click reaction. The alkyne, 1,7-octadiyne, was added to the 3-mercaptopropyl silica gel, then crosslinked using 1,6-hexanedithiol. Elemental analysis showed low octadiyne ligand surface coverage, but, stoichiometrically, three sulfurs were added to each octadiyne ligand during the crosslinking step, indicating that crosslinking occurred. The effect of the crosslinking on the stability was tested with a 50:50 (v/v) pH 0.50 5% TFA aqueous:acetonitrile mobile phase at 70 °C for six days, over 35,000 column volumes. The stationary phase showed good stability with the retention of triphenylene decreasing only 20% during that time. The Tanaka test showed that the phase has a methylene selectivity of 1.20 ± 0.04, a high shape selectivity of 2.71 ± 0.03, and a 3.98 ± 0.05 cation-exchange factor at pH 2.70. The phase has a selectivity factor for nitrobenzene and benzene of 1.41 ± 0.01, indicating the electron donating charge transfer characteristic of the phase. The mixed-mode characteristics of the phase were investigated using a mixture of the monoamine neurotransmitters norepinephrine, dopamine, and serotonin. Baseline resolution of the monoamines could be obtained using a simple 20 mM potassium phosphate (pH 2.70)/methanol mobile phase. Altering both the methanol content and the potassium ion concentration altered the retention of the monoamines indicating mixed-mode cation exchange characteristic of the crosslinked stationary phase., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

In this study, we investigated the tannic acid (TA)-, Ca 2+ -, and mica-enabled interfacial assembly of nC 60 fullerene (FWS) and Na-saturated kaolinite (Na-Kl) with in and ex situ atomic force microscopy (AFM). The epitaxial growth of herringbone motif, two dimensional (2D) chiral clusters and 3D mounds were detected. π-π electron donor-acceptor (EDA) interactions drove the transformation of the FWS, and the symmetry of the muscovite substrate directed the epitaxial ordering of self-assembled herringbone motifs. A ternary mixture of Na-Kl/FWS/TA in the presence of Ca 2+ produced double-stranded (ds) helices and 2D platelets of chiral clusters with a nano-porous monolayer on K + -treated muscovite surfaces. The weak hydration of exchangeable K + and stronger electric fields possibly contributed to the 1D and 2D propagation of aggregates. However, the local increment in carbon content due to the nucleation of functionalized FWS on mica diminished the K + -induced electric field effect and facilitated the 3D growth of helical mounds. The diffusion limited mass-transfer of particulates across the Ehrlich-Schwoebel barrier (ESB) and screw dislocation assisted motion of particulates specifically at higher steps aided mound growth. Thus, the structural incorporation of FWS can substantially impede its interfacial transport and produce hierarchical hybrid mineral-enriched graphitic aggregates., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The development of nanotheranostic agent with imaging-guided highly therapeutic efficiency has attracted most attentions on tumor treatment. Herein, the novel MoSe 2 /Bi 2 Se 3 nanosheets were designed to integrate CT/photothermal (PT) imaging and photodynamic/photothermal/chemo-therapy (PTT/PDT/chemotherapy) into one nanoplatform. Firstly, the MoSe 2 nanosheets (5-30 nm) were prepared via ultrasound-assisted exfoliated method, and then by a cation-exchange strategy the novel sandwich nanostructure Bi 2 Se 3 /MoSe 2 /Bi 2 Se 3 (Bi-M-3) were obtained, revealing the narrower band gap (1.17 eV) and the stronger near-infrared (NIR) absorption. Both experimental and density functional theory (DFT) calculations reveal the Z-scheme mechanism of charge transfer in the heterostructure, which induces the enhanced ROS (⋅OH) generation due to the efficient separation of photogenerated electron-hole pairs. Meanwhile, the nanoheterostructure also makes sure the improved photothermal conversion efficiency (59.3%). Besides, we also found the photothermal effect can promote the transfer photo-generated electron that is in favor of ROS generation. Furthermore, because of the higher absorption coefficient of X-ray for Bi atom, the heterostructure also exhibits the higher CT imaging contrast than pure MoSe 2 sample. After the loading of anticancer drug Doxorubicin (Dox), Bi-M-3@PEG-Dox displays the acid/photothermal sensitive drug release behavior. The synergistic effect of chemotherapy, photodynamic and photothermal therapy further induces the superior cancer cell apoptosis and enhanced antitumor effect., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Mixed-mode chromatography (MMC) has pronounced advantages in the separation and analysis of complex samples. Compared with single-mode chromatography, the solute retention in MMC is controlled by multiple interactions, and the retention mechanism is more complicated. In this work, two thioether-embedded benzenesulfonate silica single-ligand and mixed-ligand stationary phases were prepared by thiol-ene click chemistry. The retention mechanisms of four basic drugs were investigated under various mobile phase compositions (pH, ionic and solvent strength). The results showed that both stationary phases have the mixed retention mechanism of the reverse phase and ion exchange. By changing the salt concentration of the mobile phase, the relationship between the retention factors of basic drugs and the reciprocal of ionic strength were investigated. The results indicate that a three-interaction-form model, containing reversed-phase, pure ion-exchange, and hydrophobically assisted ion-exchange interaction, is more suitable for the mechanism study of MMC. The quantitative results demonstrate that ion-exchange interaction composed of pure ion-exchange and hydrophobically assisted ion-exchange interaction is dominated on two phases. The relative contribution of each mechanism was varied with the solute, mobile phase composition, and ligand type and ratio. In addition, the hydrophobically assisted ion-exchange interaction had a significant impact on the solute retention and separation selectivity. These fundamental studies on the MMC retention mechanism are of great theoretical significance for the novel stationary phase design and the optimization of complex sample separation.

New cation exchanger monolithic stationary phases were prepared by immobilization of three different calixarene derivatives (i.e. tetracarboxylate calix[4]arene, CLX-COO, tetrasulfonate calix[4]arene, CLX-SO 3 , and tetraphosphonate calix[4]arene, CLX-PO 4 ) onto a monolithic cryogel support (i.e. poly(2-hydroksyethylmethacrilate-co-glycidyl methacrylate, P) and investigated with respect to preparative protein chromatography. The obtained monoliths were characterized through various techniques such as FTIR spectroscopy, isoelectric point measurements, titrimetric analyses, and mercury intrusion porosimetry. Protein retention was investigated using some model proteins (i.e. lysozyme, cytochrome c, and ɑ-chymotrypsinogen A, human serum albumin, and myoglobin), and the role of modifier (i.e. NaCl) concentration and pH was thoroughly analyzed under isocratic and gradient elution conditions. Overloading experiments were also conducted to study dynamic adsorption capacity and the obtained values were found to be ranging between 3 and 8 mg/mL depending on the type of calixarene molecule. Hence, higher or comparable protein adsorption capacities were seen to be applicable on calixarene-immobilized cryogels when compared to any other functionalized cryogels in the literature. Combined with the favorable properties of these monoliths, with respect to mass transport of large molecules, these results qualify calixarene functionalized monolithic cryogels as promising stationary phases for protein preparative purification., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Porous single-crystalline nanostructures are of tremendous interest for their application in the catalytic, electronic and sensing fields due to their large active surfaces, favorable diffusion, and good electronic transport. Despite the recent advances of various other components, photoelectric chalcogenides remain almost undeveloped. The present study contributes a facile strategy to prepare porous single-crystalline CdSe nanobelts through a cation-exchange reaction, in which ZnSe⋅0.5 N 2 H 4 hybrid nanobelts are employed as precursors. The detailed characterizations indicate the preservation of the belt-like morphology of the precursors due to the spatial confinement effect, which arises from the coated surfactant layer during the cation-exchange process. Simultaneously, CdSe nanobelts with porous and single-crystalline structures are formed following a complete exchange between Zn 2+ and Cd 2+ , the release of N 2 H 4 , and the atomic arrangement. The native photoelectric properties of the as-prepared porous single-crystalline CdSe nanobelts are systematically addressed based on the nanodevices fabricated with a single nanobelt and assembled nanobelt array. The results indicate that they present a rapid, stable, and repeatable photoelectric response. Moreover, as-prepared nanobelts exhibit highly selective photoelectric sensing toward Cu 2+ with a low detection limit down to 0.1 ppm. To illuminate this phenomenon, a possible sensing mechanism is also discussed., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Alkali-exchanged SSZ-13 adsorbents were investigated for their applicability in separating N 2 from CO 2 in flue gas streams using a dynamic breakthrough method. In contrast to IAST calculations based on equilibrium isotherms, K + exchanged SSZ-13 was found to yield the best N 2 productivity, comparable to Ni-MOF-74, under dynamic conditions where diffusion properties play a significant role. This was attributed to the selective, partial blockage of access to the chabazite cavities, enhancing the separation potential in a 15/85 CO 2 /N 2 binary gas mixture.

A mixed-mode polymer monolithic column functionalized by arsonic acid groups was prepared by single-step in situ copolymerization of monomers p-methacryloylaminophenylarsonic acid (p-MAPHA) and pentaerythritol triacrylate (PETA). The prepared poly(p-MAPHA-co-PETA) monolithic column has a homogeneous monolithic structure with good permeability and mechanical stability. Zeta potential measurements reveal that the monolithic stationary phase holds a negative surface charge when the mobile phase resides in the pH range of 3.0-8.0. The retention mechanisms of prepared monolithic column are explored by the separation of selected polycyclic aromatic hydrocarbons (PAHs), nucleosides, and three basic compounds. The results indicate that the column functions in three different separation modes associated with reversed-phase chromatography based on hydrophobic interaction, hydrophilic interaction chromatography, and cation-exchange chromatography. The column efficiency of prepared monolithic column is estimated to be 70,000 and 76,000 theoretical plates/m for thiourea and naphthalene, respectively, at a linear flow velocity of 0.85 mm/s using acetonitrile/H 2 O (85/15, v/v) as the mobile phase. Furthermore, an analysis of the retention factors obtained for the PAHs indicates that the prepared monolithic column exhibits good reproducibility with relative standard deviations of 2.9%, 4.0%, and 4.7% based on run-to-run injections, column-to-column preparation, and batch-to-batch preparation, respectively. Finally, we investigate the separation performance of the proposed monolithic column for select phenols, sulfonamides, nucleobases and nucleosides., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Fabrication of membrane adsorbers with elevated binding capacity and high throughput is highly desired for simplifying and improving purification efficiencies of bioproducts (biotherapeutics, vaccines, etc.) in the biotechnological and biopharmaceutical industries. Here we demonstrate the preparation of a novel class of self-supported, cellulose-graft-polypropionic acid (CL-g-PPA) cation-exchange nanofiber membrane adsorbers under mild reaction conditions for the purification of positively charged therapeutic proteins. In our fabrication method, acrylonitrile was first polymerized and surface grafted onto cellulose nanofibers using cerium ammonium nitrate as a redox initiator to form cellulose-g-polyacrylonitrile (CL-g-PAN). CL-g-PAN was then submitted to a hydrolyzation reaction to form CL-g-PPA cationic membrane adsorbers. Morphology and structural characterization illustrated the formation of CL-g-PPA membranes with uniform coating of polyacid nanolayers along the individual nanofibers without disturbing the nanofiber structure. Benefiting from these numerous cationic polyacid binding sites and inherent large surface area and open porous structure, CL-g-PPA nanofiber membrane adsorbers showed a lysozyme static adsorption capacity of 1664 mg/g of nanofibers. These membranes showed a lysozyme dynamic binding capacity of 508 mg/g of nanofibers at 10% breakthrough (equivalent to 206 g/L capacity), with a residence time of less than 6 s. Moreover, CL-g-PPA self-supported nanofibers displayed excellent structural stability and reversibility after several cycles of protein binding studies. This dynamic binding capacity of the CL-g-PPA nanofiber membranes was 3.2 times higher than that of macroporous cellulose membranes and 8.5 times higher than that of the Sartobind S commercial membrane adsorber. Considering the simple fabrication method employed, excellent protein adsorption capacity, remarkable structural stability, and reusability, CL-g-PPA nanofiber membranes provided a versatile platform for the chromatographic separations of biomolecules (e.g., proteins, nucleic acids, and viral vaccines) as well as water purification and similar ion-exchange applications.

The distribution behavior of amphoteric 8-quinolinol (HQ) between ionic liquid (IL) phase and aqueous phase and ionic liquid chelate extraction behavior of iron(III) with HQ were investigated using four 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C n mimTf 2 N, n = 2, 4, 6 and 8) ILs. Not only neutral HQ but also cationic H 2 Q + were distributed into the IL phase, and the latter distribution based on cation-exchange with C n mim + was pronounced in the use of IL having a less-hydrophobic cation, such as C 2 mim + . In the IL chelate extraction of iron(III), the extractability increased with the increase in the hydrophobicity of IL as the extraction phase. Nevertheless, the determined equilibrium constants for the extraction as the neutral complex FeQ 3 were similar to one another. The difference in the extractability among the ILs was due to the difference in the distribution of H 2 Q + into the extraction phase. In addition, the cationic coordinatively-unsaturated complex FeQ 2 + was also extracted in use of less-hydrophobic C 2 mimTf 2 N.

As research, development, and manufacturing of biosimilar protein therapeutics proliferates, there is great interest in the continued development of a portfolio of complementary analytical methods that can be used to efficiently and effectively characterize biosimilar candidate materials relative to the respective reference (i.e., originator) molecule. Liquid phase separation techniques such as liquid chromatography and capillary electrophoresis are powerful tools that can provide both qualitative and quantitative information about similarities and differences between reference and biosimilar materials, especially when coupled with mass spectrometry. However, the inherent complexity of these protein materials challenges even the most modern one-dimensional (1D) separation methods. Two-dimensional (2D) separations present a number of potential advantages over 1D methods, including increased peak capacity, 2D peak patterns that can facilitate unknown identification, and improvement in the compatibility of some separation methods with mass spectrometry. In this study, we demonstrate the use of comprehensive 2D-LC separations involving cation-exchange (CEX) and reversed-phase (RP) separations in the first and second dimensions to compare 3 reference/biosimilar pairs of monoclonal antibodies (cetuximab, trastuzumab and infliximab) that cover a range of similarity/disimilarity in a middle-up approach. The second dimension RP separations are coupled to time-of-flight mass spectrometry, which enables direct identification of features in the chromatograms obtained from mAbs digested with the IdeS enzyme, or digestion with IdeS followed by reduction with dithiothreitol. As many as 23 chemically unique mAb fragments were detected in a single sample. Our results demonstrate that these rich datasets enable facile assesment of the degree of similarity between reference and biosimilar materials.

CdS-polyaniline-Pt and ZnS-polyaniline-Pt micromotors have been synthesized and characterized. The nanocrystals are generated "in situ" during the template electrosynthesis of the micromotors while being simultaneously trapped in the polymeric network, generating a hybrid structure. The presence of nanocrystal "edges" in the inner polyaniline layer result in a rough Pt catalytic surface and enhanced electron transfer for highly efficient bubble propulsion at remarkable speeds of over 2500 μm/s. The incorporation of CdS and ZnS nanocrystals impart several attractive functions, including cation-exchange based chemical transformation capabilities and enhanced photocatalytic performance. The remarkable ion-exchange properties of ZnS-polyaniline (PANI)-Pt micromotors are illustrated for the cation exchange of heavy metals cations. The superior photocatalytic performance of CdS-PANI-Pt micromotors is used for the enhanced photocatalytic oxidation of bisphenol A. Such self-propelled micromotors act as highly efficient dynamic platforms that offer significantly shorter and more efficient processes as compared with common static operations. The attractive properties of these micromotors will pave the way for diverse sensing, decontamination, energy generation, or electronic applications.

Ion-exchange (IEX) and Donnan dialysis (DD) are techniques which can selectively remove cations, limiting scaling in reverse osmosis (RO). If the RO concentrate could be recycled for regeneration of these pre-treatment techniques, RO recovery could be largely increased without the need for chemical addition or additional technologies. In this study, two different RO feed streams (treated industrial waste water and simple tap water) were tested in the envisioned IEX-RO and DD-RO hybrids including RO concentrate recycling. The efficiency of multivalent cation removal depends mainly on the ratio of monovalent to multivalent cations in the feed stream, influencing the ion-exchange efficiency in both IEX and DD. Since the mono-to-multivalent ratio was very high in the waste water, the RO recovery could potentially be increased to 92%. For the tap water, these high RO recoveries could only be reached by adding additional NaCl, because of the low initial monovalent to multivalent ratio in the feed. In both cases, the IEX-RO hybrid proved to be most cost-efficient, due to the high current cost of the membranes used in DD. The membrane cost would have to decrease from ±300 €/m² to 10-30 €/m² - comparable to current reverse osmosis membranes - to achieve a comparable cost. In conclusion, the recycling of RO concentrate to regenerate ion exchange pre-treatment techniques for RO is an interesting option to increase RO recovery without addition of chemicals, but only at high monovalent/multivalent cation-ratios in the feed stream., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The potential of enhanced-fluidity liquid chromatography, a subcritical chromatography technique, in mixed-mode hydrophilic interaction/strong cation-exchange separations is explored, using amino acids as analytes. The enhanced-fluidity liquid mobile phases were prepared by adding liquefied CO 2 to methanol/water mixtures, which increases the diffusivity and decreases the viscosity of the mixture. The addition of CO 2 to methanol/water mixtures resulted in increased retention of the more polar amino acids. The "optimized" chromatographic performance (achieving baseline resolution of all amino acids in the shortest amount of time) of these methanol/water/CO 2 mixtures was compared to traditional acetonitrile/water and methanol/water liquid chromatography mobile phases. Methanol/water/CO 2 mixtures offered higher efficiencies and resolution of the ten amino acids relative to the methanol/water mobile phase, and decreased the required isocratic separation time by a factor of two relative to the acetonitrile/water mobile phase. Large differences in selectivity were also observed between the enhanced-fluidity and traditional liquid mobile phases. A retention mechanism study was completed, that revealed the enhanced-fluidity mobile phase separation was governed by a mixed-mode retention mechanism of hydrophilic interaction/strong cation-exchange. On the other hand, separations with acetonitrile/water and methanol/water mobile phases were strongly governed by only one retention mechanism, either hydrophilic interaction or strong cation exchange, respectively., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Micro-capillary film (MCF) membranes are effective platforms for bioseparations and viable alternatives to established packed bed and membrane substrates at the analytical and preparative chromatography scales. Single hollow fibre (HF) MCF membranes with varied microstructures were produced in order to evaluate the effect of the bore fluid composition used during hollow fibre extrusion on their structure and performance as cation-exchange adsorbers. Hollow fibres were fabricated from ethylene-vinyl alcohol (EVOH) copolymer through solution extrusion followed by nonsolvent induced phase separation (NIPS) using bore fluids of differing composition (100wt.% N-methyl-2-pyrrolidone (NMP), 100wt.% glycerol, 100wt.% water). All HFs displayed highly microporous and mesoporous microstructures, with distinct regions of pore size <1μm, 5-15μm and up to 50μm in diameter, depending upon proximity to the bore fluid. Scanning electron microscopy (SEM) revealed skins of pore size <1μm at the inner surface of HFs produced with water and glycerol, while NMP bore fluid resulted in a skinless inner HF surface. The HFs were modified for chromatography by functionalising the polymer surface hydroxyl groups with sulphonic acid (SP) groups to produce cation-exchange adsorbers. The maximum binding capacities of the HFs were determined by frontal analysis using lysozyme solutions (0.05-100mgml(-1)) for a flow rate of 1.0mlmin(-1). The NMP-HF-SP module displayed the largest maximum lysozyme binding capacity of all the fibres produced (40.3mg lysozyme/ml adsorbent volume), a nearly 2-fold increase over the glycerol and 10-fold increase over the water variants at the same sample flow rate. The importance of NMP as a bore fluid to hollow fibre membrane performance as a result of inner surface porosity was established with a view to applying this parameter for the optimisation of multi-capillary MCF performance in future studies., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A solid-phase microextraction (SPME) method based on a sampler coating that includes strong cation groups (C18/SCX) is explored as a rapid direct sampling tool to detect and quantify freely dissolved basic drugs. Sampling kinetics, sorption isotherms and competitive effects on extraction yields in mixtures were tested for amphetamine and the relatively large/hydrophobic tricyclic antidepressant amitriptyline. Both compounds are >99% ionized at pH 7.4 but their affinity for the C18/SCX fiber is markedly different with distribution coefficients (Dfw values) of 2.49±0.02 for amphetamine and 4.72±0.10 for amitriptyline. Typical changes in electrolyte homeostasis that may occur in biomedical samples were simulated by altering pH and ionic composition (Na(+) and K(+) concentrations). These changes were shown to affect C18/SCX sorption affinities of the tested drugs with less than 0.2log units. At relatively low fiber loadings (<10mmol/L coating) and at all tested exposure times, linear sorption isotherms were obtained for both compounds but at aqueous concentrations of the individual drugs corresponding to concentrations in blood that are lethal, sorption isotherms became strongly nonlinear. Competition effects within binary mixtures occurred only if combinations of aqueous concentrations resulted in total fiber loadings that were in the nonlinear range of the SPME sorption isotherm for the individual compounds. We also compared sorption to the (prototype) C18/SCX SPME coating with analogue (biocompatible) C18 coated SPME fibers. C18/SCX fibers show increased sorption affinity for cationic compounds compared to C18 fibers, as tested using amitriptyline, amphetamine and trimethoprim. Surprisingly, sorption affinity of these ionized compounds for the C18 SPME fibers were within 1log unit of the C18/SCX SPME fibers. This shows that the strong cation exchange groups within the C18/SCX coating only has a relatively small contribution to the total sorption affinity of cationic compounds. Also the role of negatively charged silanol groups in both the C18 and C18/SCX coating seems small, as anionic diclofenac species sorbed strongly to the C18 fiber. Ionized organic species seem to be substantially adsorbed to the high surface area of C18 in SPME types using porous silica based coatings., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Core-shell PbS-CdS quantum dots enhance the peak external quantum efficiency of shortwave-infrared light-emitting devices by up to 50-100-fold (compared with core-only PbS devices). This is more than double the efficiency of previous quantum-dot light-emitting devices operating at wavelengths beyond 1 μm, and results from the passivation of the PbS cores by the CdS shells against in situ photoluminescence quenching., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

It is well known that metals with higher electron affinity like Au tend to undergo reduction rather than cation-exchange. It is experimentally shown that under certain conditions cation-exchange is dominant over reduction. Thermodynamic calculation further consolidates the understanding and paves the way for better predictability of cation-exchange/reduction reactions for other systems., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A passive sampler tool (solid-phase microextraction, SPME) was optimized to measure freely dissolved concentrations (Cw,free) of lauryl diethanolamine (C12-DEA). C12-DEA can be protonated and act as a cationic surfactant. From the pH-dependent sorption to neutral SPME coatings (polyacrylate and PDMS), a pKa of 8.7 was calculated, which differs more than two units from the value of 6.4 reported elsewhere. Polyacrylate coated SPME could not adequately sample largely protonated C12-DEA in humic acid solutions of pH 6. A new hydrophobic SPME coating with cation-exchange properties (C18/SCX) sorbed C12-DEA 100 fold stronger than polyacrylate, because it specifically sorbs protonated C12-DEA species. The C18/SCX-SPME fiber showed linear calibration isotherms in a concentration range of <1 nM-1 μM (well below the CMC). Using the C18/SCX-SPME fibers, linear sorption isotherms to Aldrich humic acid at pH 6 (ionic strength 0.015 M) were measured over a broad concentration range with a sorption coefficient of 10(5.3)., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Dissolved organic nitrogen (DON) can act as a precursor of nitrogenous disinfection byproducts during oxidative water treatment. Quantification and characterization of DON are still challenging for waters with high concentrations of dissolved inorganic nitrogen (DIN, including ammonia, nitrate and nitrite) relative to total dissolved nitrogen (TDN) due to the cumulative analytical errors of independently measured nitrogen species (i.e., DON = TDN - NO2(-) - NO3(-) - NH4(+)/NH3) and interference of DIN species to TDN quantification. In this study, a novel electrodialysis (ED)-based treatment for selective DIN removal was developed and optimized with respect to type of ion-exchange membrane, sample pH, and ED duration. The optimized ED method was then coupled with size-exclusion chromatography with organic carbon, UV, and nitrogen detection (SEC-OCD-ND) for advanced DON analysis in wastewater effluents. Among the tested ion-exchange membranes, the PC-AR anion- and CMT cation-exchange membranes showed the lowest DOC loss (1-7%) during ED treatment of a wastewater effluent at ambient pH (8.0). A good correlation was found between the decrease of the DIN/TDN ratio and conductivity. Therefore, conductivity has been adopted as a convenient way to determine the optimal duration of the ED treatment. In the pH range of 7.0-8.3, ED treatment of various wastewater effluents with the PC-AR/CMT membranes showed that the relative residual conductivity could be reduced to less than 0.50 (DIN removal >90%; DIN/TDN ratio ≤ 0.60) with lower DOC losses (6%) than the previous dialysis and nanofiltration methods (DOC loss >10%). In addition, the ED method is shorter (0.5 h) than the previous methods (>1-24 h). The relative residual conductivity was further reduced to ≈ 0.20 (DIN removal >95%; DIN/TDN ratio ≤ 0.35) by increasing the ED duration to 0.7 h (DOC loss = 8%) for analysis by SEC-OCD-ND, which provided new information on distribution and ratio of organic carbon and nitrogen in different molecular weight fractions of effluent organic matter., (Copyright © 2013 Elsevier Ltd. All rights reserved.)