Liquid Phase Separation Technique Research Articles

Enhanced ethanol vapor sensing by 2D CuO-ZnO composite at ambient conditions

Gas sensors find application in the fields of food packaging, medical, agriculture, industries, transport, storage, and warehousing, etc. An efficient gas sensor should be sensitive and selective towards analyte, have fast response and recovery time and operate under moderate conditions. The commercial sensors have an in-built heating element. Thus, there is scope for finding materials that can function as room temperature ethanol sensors. Here, a composite of two-dimensional copper oxide (CuO) with zinc oxide (ZnO) nanoparticles is reported as a potential ethanol (EtOH) vapor sensor under ambient conditions. CuO is synthesized with the help of liquid–liquid phase separation technique yielding architecturally aligned 2D structures. ZnO nanoparticles are synthesized via microwave assisted wet chemical route separately. X-ray diffraction studies show the phase formation of pure CuO and ZnO individually. The CuO and ZnO samples are ground mechanically in 1:1 wt ratio to form a composite referred to as CZC. The optical absorption studies show bandgap of CuO structures as 1.41 eV, ZnO as 3.13 eV, and of CZC as 1.24 eV. A slurry of the composite is then coated on a glass substrate to study the resistance changes after ethanol vapor exposure. It is observed that while pure CuO is almost unresponsive to EtOH vapors, ZnO has sluggish response, the CZC samples responded fast. The best average response time is observed to be ∼ 4 sec while recovery time is ∼ 12 sec. The sensors show good reversibility as they return to their initial state without applying any heat treatment. The change in EtOH sensing in composites is attributed to the formation of heterojunction between CuO-ZnO which facilitates faster electron transfer across the heterojunction and the presence of large surface area renders an increased number of adsorption sites.

Proceedings of APCE-CECE-ITP-IUPAC 2022

In a demonstration of modern analytical chemistry at its best, the International Interdisciplinary Conference of Chemical Analysis, APCE-CECE-ITP-IUPAC 2022 was held after two years of COVID-19-related delays in Siem Reap, Cambodia. The quadruple meeting included: 18th Asia Pacific International Symposium on Microscale Separations and Analyses, 17th International Interdisciplinary Meeting on Bioanalysis, 28th International Symposium on Electro- and Liquid Phase-Separation Techniques, and IUPAC Special Symposia by Division of Chemistry and the Environment. While, under normal circumstances, these conferences would take place in different countries, we have decided to bring together analytical chemists from all over the world for a conference covering all aspects of modern analytical chemistry. Our goal remained the same: “bring together scientists from different disciplines who may not meet at other meetings”. With plenary and invited lectures delivered by distinguished scientists, this in-person meeting allowed to broaden our knowledge, meet new friends, and start new collaborations. The organizers want to thank all speakers, sponsors, and participants for their support. Please, check the conference web for more information about the history, programs, photos, and videos.

Capillary Electrophoresis Plasma Fractionation for Lipids Analysis.

Extraction of lipids has mainly used density liquid phase separation techniques; however, these methods are limited by their broad extraction and lack specificity. Complex mixtures like blood plasma contain multiple lipid classes, whose distribution in the body are mediated by protein-lipid interactions and integration of lipids in larger lipoprotein complexes. The capillary electrophoresis system separates complex mixtures by electrokinetic forces that preserve protein-lipid complexation and allow for the fractionation of samples. Here we present a methodology for fractionating plasma using the capillary electrophoresis system.

Simple, Reliable Protocol for High-Yield Solubilization of Seedless Amyloid-β Monomer.

Self-assembly of the amyloid-β (Aβ) peptide to form toxic oligomers and fibrils is a key causal event in the onset of Alzheimer's disease, and Aβ is the focus of intense research in neuroscience, biophysics, and structural biology aimed at therapeutic development. Due to its rapid self-assembly and extreme sensitivity to aggregation conditions, preparation of seedless, reproducible Aβ solutions is highly challenging, and there are serious ongoing issues with consistency in the literature. In this paper, we use a liquid-phase separation technique, asymmetric flow field-flow fractionation with multiangle light scattering (AF4-MALS), to develop and validate a simple, effective, economical method for re-solubilization and quality control of purified, lyophilized Aβ samples. Our findings were obtained with recombinant peptide but are physicochemical in nature and thus highly relevant to synthetic peptide. We show that much of the variability in the literature stems from the inability of overly mild solvent treatments to produce consistently monomeric preparations and is rectified by a protocol involving high-pH (>12) dissolution, sonication, and rapid freezing to prevent modification. Aβ treated in this manner is chemically stable, can be stored over long timescales at -80 °C, and exhibits remarkably consistent self-assembly behavior when returned to near-neutral pH. These preparations are highly monomeric, seedless, and do not require additional rounds of size exclusion, eliminating the need for this costly procedure and increasing the flexibility of use. We propose that our improved protocol is the simplest, fastest, and most effective way to solubilize Aβ from diverse sources for sensitive self-assembly and toxicity assays.

A novel strategy of fabricated flexible ITO electrode by liquid metal ultra-thin oxide film

Flexible transparent conductive films are gaining attention day by day over the last few years due to it is a key component of next generation flexible electronics and optoelectronic devices. Indium tin oxide (ITO) as one of the most widely used transparent conductive material is limited by the traditional deposition approach cannot be achieve ultra-thin, which results in its brittle nature. Herein, a novel strategy for fabricating highly transparent conductive films by liquid metal interface phase separation technique based on low-melting liquid metal of InxSn100-x alloy is reported, during the solid-to-liquid phase transition of alloy, the monolayer of surface oxide film segregated with the bulk phase and was printed on the flexible polyethylene-naphthalate (PEN) substrate under the van der Waals. This novel strategy can directly print the ultra-thin self-oxide with the structure of ITO on PEN substrate, with the resulting of transparency over 97.5% and resistivity as low as 0.21 kΩ cm, providing a new way of low-cost raw ITO material as well as the personalized preparation strategy. The desirable highly transparent conductive films are comparable to recently reported ITO film, together with advantages of pretty steady, make them attractive as various flexible transparent conductive electrodes, for example, an ultra-thin ITO film is developed for luminescent devices.

Recent advances in microscale separation techniques for lipidome analysis.

This review paper highlights the recent research on liquid-phase microscale separation techniques for lipidome analysis over the last 10 years, mainly focusing on capillary liquid chromatography (LC) and capillary electrophoresis (CE) coupled with mass spectrometry (MS). Lipids are one of the most important classes of biomolecules which are involved in the cell membrane, energy storage, signal transduction, and so on. Since lipids include a variety of hydrophobic compounds including numerous structural isomers, lipidomes are a challenging target in bioanalytical chemistry. MS is the key technology that comprehensively identifies lipids; however, separation techniques like LC and CE are necessary prior to MS detection in order to avoid ionization suppression and resolve structural isomers. Separation techniques using μm-scale columns, such as a fused silica capillary and microfluidic device, are effective at realizing high-resolution separation. Microscale separation usually employs a nL-scale flow, which is also compatible with nanoelectrospray ionization-MS that achieves high sensitivity. Owing to such analytical advantages, microscale separation techniques like capillary/microchip LC and CE have been employed for more than 100 lipidome studies. Such techniques are still being evolved and achieving further higher resolution and wider coverage of lipidomes. Therefore, microscale separation techniques are promising as the fundamental technology in next-generation lipidome analysis.

Separation and screening of antioxidant peptides from Scomberomorus niphonius based on nano flow liquid chromatography

As a rich source of high activity antioxidant peptides, Scomberomorus niphonius is a key marine natural product with a high processing value. Due to the high complexity of fish tissues, high recovery extraction and high efficiency screening of the active antioxidant peptide species have become the major challenges for the research and development of preparation and separation techniques. Due to the high specificity of hydrolytic enzymes, when different types of enzymes are used for the hydrolysis of fish tissues, the resultant active peptides may have significant differences in chemical structures, biological functions, and physical activities. In this study, in order to obtain antioxidant peptides with high activity and functionality, defatted visceral powder of Scomberomorus niphonius was used as a raw material for sample preparation. Five hydrolytic enzymes (flavor protease, trypsin, acid protease, neutral protease, and alkaline protease) were selected and investigated for their hydrolyzing efficiencies in visceral solutions of Scomberomorus niphonius, according to their optimum hydrolyzing conditions. The diphenyl bitter hydrazine radical (DPPH·) scavenging rate, hydroxyl radical (·OH) scavenging rate, and degree of hydrolysis (DH) were adopted as indicators for hydrolytic enzyme selection and optimization. The data suggested that, among all the hydrolytic enzymes investigated, trypsin presented the best scavenging capabilities for both DPPH· and ·OH species, with scavenging rates of 88.93%±0.82% for DPPH· and 53.09%±0.73% for ·OH, respectively. Based on the single-factor test results, the DPPH· scavenging rate was further utilized as an indicator and was found to depend on the hydrolytic enzyme quantity, hydrolyzation temperature, and hydrolyzation time. According to the Box-Behnken center composed experimental design, a triple factor and triple level response surface method was adopted for further optimization of antioxidant peptide preparation from Scomberomorus niphonius viscera. The preparation method was systematically optimized, and as a result, a degree of hydrolysis of 23.66%, DPPH· scavenging rate of 93.78%, and ·OH scavenging rate of 62.59% were achieved. High performance nano flow liquid chromatography is a new generation micro scale liquid phase separation technique that has the advantages of low sample requirement, low solvent consumption, and high efficiency. In this study, we applied this method to marine natural product purification. In order to screen the most suitable chromatographic stationary phase for the separation and analysis of active antioxidant peptides from Scomberomorus niphonius viscera, a nano flow reversed-phase C18 column (15 cm×100 μm, 5 μm, 30 nm) and a strong cation exchange column (15 cm×100 μm, 5 μm, 100 nm) were investigated. A nano flow high performance liquid chromatography platform with a 1:1000 splitting ratio was adopted for this study. Using the enzyme-hydrolyzed solution from Scomberomorus niphonius viscera as the sample, following filtration, the antioxidant peptides were separated, collected, freeze-dried, and finally tested for their antioxidant capability. The results showed that the strong cation exchange phase was more suitable for antioxidant peptide isolation and purification from Scomberomorus niphonius viscera, and an antioxidant peptide component with high activity was successfully screened. During the activity test, the 50% inhibition concentration (IC50) value of the DPPH· scavenging capability of this peptide was 0.672±0.051 mg/mL, which was 13.6 times higher than the activity value before the peptide species was purified. The current study for the first time reports the application of high performance nano flow liquid chromatography in the purification and analysis of antioxidant peptides from a marine natural product source and also demonstrates the effectiveness and future prospect of the use of nano flow ion exchange chromatography for high performance separation and high efficiency screening of antioxidant peptides.

N-glycan Analysis in Molecular Medicine: Innovator and Biosimilar Protein Therapeutics.

The market segment of new biological drugs (monoclonal antibodies, fusion proteins, antibody-drug conjugates, and new modality protein therapeutics) is rapidly growing, especially after the patent expiration of the original biologics, initiating the emergence of biosimilars. N-glycosylation of therapeutic proteins has high importance on their stability, safety, immunogenicity, efficacy, and serum half-life. Therefore, Nglycosylation is considered to be one of the critical quality attributes. Consequently, it should be rigorously monitored during the development, manufacturing, and release of glycoprotein biologicals. In this review, first, the regulatory considerations for biosimilars are shortly summarized, followed by conferring the analytical techniques needed for monitoring and characterization of the N-glycosylation of biological drugs. Particular respect is paid to liquid phase separation techniques with high sensitivity and highresolution detection methods, including laser-induced fluorescence and mass spectrometry.

Various Strategies in Post-Polymerization Functionalization of Organic Polymer-Based Monoliths Used in Liquid Phase Separation Techniques.

This review article is aimed at summarizing the various strategies that have been developed so far for post-polymerization functionalization (PPF) of organic polymer-based monoliths used in liquid phase separation techniques, namely HPLC at all scales and capillary electrochromatography (CEC). The reader will find the organic reactions performed on monolithic columns for grafting the chromatographic ligands needed for solving the separation problems on hand. This process involves therefore the fabrication of template monoliths that carry reactive functional groups to which chromatographic ligands can be covalently attached in a post-polymerization kind of approach. That is, the template monolith that has been optimized in terms of pore structure and other morphology can be readily modified and tailor made on column to fit a particular separation. The review article will not only cover the various strategies developed so far but also describe their separation applications. To the best of our knowledge, this review article will be the first of its kind.

Microcarriers with Controllable Size via Electrified Liquid Jets and Phase Separation Technique Promote Cell Proliferation and Osteogenic Differentiation.

Differently sized poly(lactic-co-glycolic) microspheres were efficiently prepared with electrified liquid jets and a phase separation technique for a wide range of applications. Higher polymer concentrations tended to form larger microcarriers. Polymer concentration can obviously affect bead or fiber formation resulting beads and fiber morphologies. As the voltage of electrostatic field and the needle size increased, the size of microcarriers decreased remarkably. The most suitable concentration of ethanol in the collecting solution might be lower than 55%. The resulting composite microcarriers have significantly narrow size distribution, controllable sizes, and high cell adhesion, growth, and osteodifferentiation abilities.

Recent advances in hyphenation of nanoflow liquid phase separation with inductively coupled plasma mass spectrometry

High-performance nanoflow liquid-phase separation techniques such as nanoflow liquid chromatography (nanoLC), capillary electrophoresis (CE), and microchip chromatography and electrophoresis (chip-ICP-MS) have been hyphenated with inductively coupled plasma mass spectrometry (ICP-MS) extensively. This hyphenation combines the excellent characteristics of the front-end separation technology, such as high selectivity, sensitivity, and speed, and low sample consumption, and the advantages of back-end ICP-MS, such as high resolution, wide dynamic range, and absolute quantification capability. Thus, such hyphenation is becoming an increasingly important analytical tool. Herein we systematically introduce the recent development of hyphenated nanoLC, CE, and chip-ICP-MS, review its application in chemical and biochemical analysis, and discuss potential future developments of hyphenating these technologies.

Polysaccharide-Based Chiral Stationary Phases for Enantioseparations by High-Performance Liquid Chromatography: An Overview.

This chapter summarizes the application of polysaccharide-based chiral stationary phases (CSPs) for separation of enantiomers in high-performance liquid chromatography (HPLC). Since this book contains dedicated chapters on enantioseparations using supercritical fluid chromatography (SFC), or capillary electrochromatography (CEC), the application of polysaccharide-based materials in these modes of liquid-phase separation techniques is touched just superficially. Special emphasis is directed toward a discussion of the optimization of polysaccharide-based chiral selectors, their attachment onto the carrier, and the optimization of the support. The optimization of the separation of enantiomers based on various parameters such as mobile phase composition and temperature is discussed.

Approaches for enantioselective resolution of pharmaceuticals by miniaturised separation techniques with new chiral phases based on nanoparticles and monolithis.

This article discusses new developments in the preparation of nanoparticles and monoliths with emphasis upon their application as the stationary and pseudo-stationary phases for miniaturised liquid phase separation techniques, which have occurred in the last 10 years (from 2006 to the actuality). References included in this review represent current trends and state of the art in the application of these materials to the analysis, by EKC, CEC and miniaturised chromatography, of chiral compounds with environmental interest such as pharmaceuticals. Due to their extraordinary properties, columns prepared with these new chiral stationary or pseudo-stationary phases, based on materials such as gold nanoparticles, metal-organic frameworks, ordered mesoporous silicas, carbonaceous materials, polymeric-based and silica-based monoliths or molecularly imprinted materials, can usually show some improvements in the separation selectivity, column efficiency and chemical stability in comparison with conventional chiral columns available commercially.

An overview of multidimensional liquid phase separations in food analysis.

Food safety is a priority public health concern that demands analytical methods capable to detect low concentration level of contaminants (e.g. pesticides and antibiotics) in different food matrices. Due to the high complexity of these matrices, a sample preparation step is in most cases mandatory to achieve satisfactory results being usually tedious, lengthy, and prone to the introduction of errors. For this reason, many research groups have focused efforts on the development of online systems capable to do the cleanup, concentration, and separation steps at once through multidimensional separation techniques (MDS). Among several possible setups, the most popular are the multidimensional chromatographic techniques (MDC) that consist in combining more than one mobile and/or stationary phase to provide a satisfactory separation. In the present review, we selected a variety of multidimensional separation systems used for food contaminant analysis in order to discuss the instrumentation aspects, the concept of orthogonality, column approaches used in these systems, and new materials that can be used in these columns. Selected classes of contaminants present in food matrices are introduced and discussed as example of the potential applications of multidimensional liquid phase separation techniques in food safety.

A facile approach toward multifunctional polyethersulfone membranes via in situ cross-linked copolymerization

In this study, multifunctional polyethersulfone (PES) membranes are prepared via in situ cross-linked copolymerization coupled with a liquid–liquid phase separation technique. Acrylic acid (AA) and N-vinylpyrrolidone (VP) are copolymerized in PES solution, and the solution is then directly used to prepare PES membranes. The infrared and X-ray photoelectron spectroscopy testing, scanning electron microscopy, and water contact angle measurements confirm the successful modification of pristine PES membrane. Protein adsorption, platelet adhesion, plasma recalcification time, and activated partial thromboplastin time assays convince that the modified PES membranes have a better biocompatibility than pristine PES membrane. In addition, the modified membranes showed good protein antifouling property and significant adsorption property of cationic dye. The loading of Ag nanoparticles into the modified membranes endows the composite membranes with antibacterial activity.

Supermacroporous chemically cross-linked poly(aspartic acid) hydrogels

Chemically cross-linked poly(aspartic acid) (PASP) gels were prepared by a solid–liquid phase separation technique, cryogelation, to achieve a supermacroporous interconnected pore structure. The precursor polymer of PASP, polysuccinimide (PSI) was cross-linked below the freezing point of the solvent and the forming crystals acted as templates for the pores. Dimethyl sulfoxide was chosen as solvent instead of the more commonly used water. Thus larger temperatures could be utilized for the preparation and the drawback of increase in specific volume of water upon freezing could be eliminated. The morphology of the hydrogels was characterized by scanning electron microscopy and interconnectivity of the pores was proven by the small flow resistance of the gels. Compression tests also confirmed the interconnected porous structure and the complete re-swelling and shape recovery of the supermacroporous PASP hydrogels. The prepared hydrogels are of interest for several biomedical applications as scaffolding materials because of their cytocompatibility, controllable morphology and pH-responsive character.

Reviews 2015

Ziad El Rassi Once more, the yearly special issue on “Reviews” continues its primary role of providing a “central review bank” in the various aspects of fundamentals, methodologies and applications of electrophoresis and other related liquid phase separation techniques (e.g., microfluidics and liquid chromatography). The present “Reviews” issue has 15 critical reviews distributed over 5 distinct parts. Part I is on ITP, sample stacking and sensitivity enhancement methods while Part II is on monoliths for LC and CEC and on chiral selectors in CE. Part III discusses recent advances in multidimensional separation approaches by CEC and CE. This is followed by Part IV, which presents some detection issues involving mass spectrometry, electrochemical detectors using carbon allotropes in both CE and MCE and capacitively coupled contactless conductivity detection. Finally, Part V is on various omics and reviews the fields of CE-MS for metabolomics, glycoproteomics and liquid phase based separation systems in proteomics (i.e., separomics). The tradition of beginning the New Year and in turn a new volume with a special issue of review articles will continue. Authors interested in contributing to the 2016 Reviews issue are encouraged to contact me and suggest the topics of their contributions. The deadline for submission of review articles will be June/July 2015 so that the special issue will be in print in January 2016. Finally, I would like to thank all the contributors for their excellent articles, which provide a broad view of the recent advances in the field. Also, I would like to wish every one including the Editors, Staff of the Journal, Authors, Reviewers and Readers a Very Happy and Prosperous New Year 2015. Ziad El Rassi Editor-In-Chief

Ionic-strength-sensitive polyethersulfone membrane with improved anti-fouling property modified by zwitterionic polymer via in situ cross-linked polymerization

A new method to prepare ionic-strength-sensitive membrane with improved anti-fouling property and blood compatibility is developed via in situ cross-linked polymerization of sulfobetaine methacrylate (SBMA) in polyethersulfone (PES) solution and a liquid–liquid phase separation technique. The modified membrane is characterized by attenuated total reflectance-Fourier transform infrared spectra (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), 1H NMR measurements, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and water contact angle (WCA) measurement. The membrane with high PSBMA content shows obvious ionic-strength-sensitive property and ionic-strength reversibility, which are expressed by the fluxes of salt solutions. Meanwhile, with the increase of the PSBMA content in the membrane, the anti-fouling property and blood compatibility are considerably improved.

Novel heparin-mimicking polymer brush grafted carbon nanotube/PES composite membranes for safe and efficient blood purification

Nowadays, polymeric membrane based hemodialysis is considered to be the most practical approach for the treatment of kidney failure. To develop advanced hemodialysis membrane integrated with favorable blood and cell compatibilities and efficient blood purification ability, novel biocompatible composite membranes consisting of heparin-mimicking polymer brush functionalized carbon nanotubes (f-CNTs) and polyethersulfone (PES) are designed. Firstly, surface initiated atom transfer polymerization (SI-ATRP) is applied to synthesize heparin-mimicking polymer brush (contained the sodium styrene sulfonate (SS) and methyl ether methacrylate (EGMA) units) grafted CNT. Then, the f-CNT/PES composite membranes are prepared by a liquid–liquid phase separation technique. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the f-CNT would not cause severe damage on the membrane morphologies. Systemic protein ultrafiltration experiment indicated that the heparin-mimicking composite membranes owned satisfied antifouling property and protein rejection ratio. Further blood compatibility evaluation revealed that the composite membranes had decreased protein adsorption, prolonged clotting time, and suppressed platelet adhesion compared to pristine PES membrane. The results of human embryonic hepatocytes (LO-2) culture revealed that the cyto-compatibility of the modified membrane was enhanced by the blending of heparin mimicking polymer functionalized CNT. Furthermore, with the addition of f-CNT, the composite membranes showed remarkably increased removal efficiency of uremic toxin. In general, the fabricated heparin-mimicking f-CNT/PES composite membranes exhibited anti-fouling ability in ultrafiltration, excellent blood and cell compatibility and efficient toxic molecules removal ratio, thus present great potential for various applications, such as hemodialysis and bio-artificial liver support. Furthermore, the proposed method might forward the fabrication of advanced hemodialysis membrane by integrating functional nanomaterials and bioactive polymers.

Hierarchically porous PVDF/nano-SiC foam for distant oil-spill cleanups

Water source contamination by virtue of oil seepage and spillage necessitates immediate measures to curtail its lethal repercussions on the oceanic ecosystem. This heavily demands for the preparation of innovative absorbents, exhibiting an excellent oil uptake capacity under various conditions. In this study, we reveal an extensively porous sorbent material coalesced with nano silicon carbide, PVDF/nano-SiC, presenting extraordinary absorption capacity, remarkable durability and easy conduct during the course of absorption. The foam was facilely fabricated via a solid–liquid phase separation technique, based on the principle of differential solubility of the polymer in the solvent (DMF) and the non-solvent (water). The inclusion of nano-SiC into the PVDF matrix increases its strength and hardness, thus eliminating the issue of the withering of the as-prepared foam in the oil–water mixture. Furthermore, the absorption capacity of the foam was determined by varying the weight percentage of nano-SiC in PVDF. Optimised absorption was achieved with a 5% w/w inclusion of nano-SiC. The absorbent allows oil to selectively permeate through it, while being completely water repellent, and absorbs up to 21.5 times and 20.5 times its weight equivalent of engine oil and paraffin oil, respectively. Furthermore, the absorbed oil could be readily removed for reuse by mechanically squeezing the foam. The foam could be reused for absorbing oils, at least four times, with a slight decline in its absorption capacity. The convincing results of this research provide an advanced alternative for cleaning massive oil spills at distant locations.