Enhancing Sensitivity in the Hyphenation of High-Performance Liquid Chromatography to Benchtop Nuclear Magnetic Resonance Spectroscopy at Isocratic and Onflow Conditions.

The onflow hyphenation of high-performance liquid chromatography (HPLC) in adsorption mode with a benchtop H nuclear magnetic resonance (NMR) spectrometer is described for the first time. Protonated solvents and isocratic conditions are used. The sensitivity was increased by choosing suitable NMR acquisition parameter as well as optimizing injection parameters and postacquisition data processing methods.

Potential of Benchtop NMR for the Determination of Polymer Molar Masses, Molar Mass Distributions, and Chemical Composition Profiles by Means of Diffusion-Ordered Spectroscopy, DOSY.

The determination of molar masses and their distributions is crucial in polymer synthesis and design. This work presents the current performance and limitations of diffusion-ordered spectroscopy (DOSY) on a low-field (benchtop) NMR spectrometer (at 90 MHz) as an alternative to size exclusion chromatography (SEC) for determining diffusion coefficient distributions (DCDs) and molar mass distributions (MMDs). After optimization for narrowly distributed homopolymers, MMDs obtained with inverse Laplace transformation (ILT) and log-normal distribution are compared with average molar masses obtained with mono- and bi-exponential fits, as well as MMDs obtained from SEC.

Boosting the Formation of Brønsted Acids on Flame-made WO/ZrO for Glucose Conversion.

Tungstate-zirconium oxide catalysts (WO/ZrO) with much higher concentrations of Brønsted acid sites (BAS) and a bigger ratio of Brønsted to Lewis acid sites (B/L) than achievable by conventional impregnation (IM) were synthesized using single-step flame spray pyrolysis (FSP). The rapid quenching and short residence time inherent to FSP prevent the accumulation of W atoms on the ZrO support and thus provide an excellent surface dispersion of WO species. As a result, FSP-made WO/ZrO (FSP-WO/ZrO) has a much higher surface concentration of three-dimensional Zr-WO clusters than corresponding materials prepared by conventional impregnation (IM-WO/ZrO).

Using Capillary Electrophoresis to Investigate Protein Conformational and Compositional Heterogeneity.

Detailed insights into protein structure/function relationships require robust characterization methodologies. Free-solution capillary electrophoresis (CE) is a unique separation technique which is sensitive to the conformation and/or composition of proteins, and therefore provides information on the heterogeneity of these properties. Three unrelated, conformationally/compositionally-altered proteins were separated by CE.

Assessing the quantification of acetylation in konjac glucomannan via ATR-FTIR and solid-state NMR spectroscopy.

Dietary fiber like konjac glucomannan (KGM) is important in maintaining good human health. There is no established method for quantifying the average degree of acetylation DA of this polysaccharide. Polysaccharides are notoriously difficult to dissolve.

Engineering the Distinct Structure Interface of Subnano-alumina Domains on Silica for Acidic Amorphous Silica-Alumina toward Biorefining.

Amorphous silica-aluminas (ASAs) are important solid catalysts and supports for many industrially essential and sustainable processes, such as hydrocarbon transformation and biorefining. However, the wide distribution of acid strength on ASAs often results in undesired side reactions, lowering the product selectivity. Here we developed a strategy for the synthesis of a unique class of ASAs with unvarying strength of Brønsted acid sites (BAS) and Lewis acid sites (LAS) using double-flame-spray pyrolysis.

Insight into Three-Coordinate Aluminum Species on Ethanol-to-Olefin Conversion over ZSM-5 Zeolites.

Commercial bioethanol can be readily converted into ethylene by a dehydration process using solid acids, such as Brønsted acidic H-ZSM-5 zeolites, and thus, it is an ideal candidate to replace petroleum and coal for the sustainable production of ethylene. Now, strong Lewis acidic extra-framework three-coordinate Al species were introduced into H-ZSM-5 zeolites to improve their catalytic activity. Remarkably, Al species working with Brønsted acid sites can accelerate ethanol dehydration at a much lower reaction temperature and shorten the unsteady-state period within 1-2 h, compared to >9 h for those without Al species, which can significantly enhance the ethanol dehydration efficiency and reduce the cost.

Characterization of oligo(acrylic acid)s and their block co-oligomers.

Oligo(acrylic acid), oligoAA are important species currently used industrially in the stabilization of paints and also for the production of self-assembled polymer structures which have been shown to have useful applications in analytical separation methods and potentially in drug delivery systems. To properly tailor the synthesis of oligoAA, and its block co-oligomers synthesized by Reversible-Addition Fragmentation chain Transfer (RAFT) polymerization to applications, detailed knowledge about the chemical structure is needed. Commonly used techniques such as Size Exclusion Chromatography (SEC) and Electrospray Ionization-Mass Spectrometry (ESI-MS) suffer from poor resolution and non-quantitative distributions, respectively.

Biohybrid cellulose fibers: Toward paper materials with wet strength properties.

Herein, we report on the preparation of novel cellulose-PEG biohybrid papers with wet strength properties. The biohybrid paper sheets are obtained using a two-step procedure where ω- or α, ω-azide functionalized PEG chains are anchored onto alkyne-functionalized wood fibers through CuAAC ligation in mild and aqueous conditions. The incorporation of the PEG grafts mostly occurs at the periphery of the cellulose fibers and degrees of substitution up to 0.

Poly(ethylene glycol) functionalization of monolithic poly(divinyl benzene) for improved miniaturized solid phase extraction of protein-rich samples.

Non-specific protein adsorption on hydrophobic solid phase extraction (SPE) adsorbents can reduce the efficacy of purification. To improve sample clean-up, poly(divinyl benzene) (PDVB) monoliths grafted with hydrophilic polyethylene glycol methacrylate (PEGMA) were developed. Residual vinyl groups (RVGs) of the PDVB were employed as anchor points for PEGMA grafting.

Capillary Electrophoresis to Monitor Peptide Grafting onto Chitosan Films in Real Time.

Free-solution capillary electrophoresis (CE) separates analytes, generally charged compounds in solution through the application of an electric field. Compared to other analytical separation techniques, such as chromatography, CE is cheap, robust and effectively requires no sample preparation (for a number of complex natural matrices or polymeric samples). CE is fast and can be used to follow the evolution of mixtures in real time (e.

Determination of the distributions of degrees of acetylation of chitosan.

Chitosan is often characterized by its average degree of acetylation. To increase chitosan's use in various industries, a more thorough characterization is necessary as the acetylation of chitosan affects properties such as dissolution and mechanical properties of chitosan films. Despite the poor solubility of chitosan, free solution capillary electrophoresis (CE) allows a robust separation of chitosan by the degree of acetylation.

Structural modifications of cellulose samples after dissolution into various solvent systems.

This work deals with the modifications resulting from the dissolution of four commercial cellulosic samples, with different crystallinity rates and degrees of polymerization (DPs), in four solvent systems, known and used to dissolve cellulose. The dissolution conditions were optimized for the 16 various systems and followed by turbidity measurements. After regeneration, the samples were analyzed by thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffractometry (XRD) to study their modification.

Towards a less biased dissolution of chitosan.

The dissolution of polysaccharides is notoriously challenging, especially when one needs a "true" solution. Factors influencing chitosan's solubility include composition, also known as degree of acetylation (DA). The dissolution of chitosan was investigated by visual observation, size-exclusion chromatography (SEC), pressure mobilization (PM), free-solution capillary electrophoresis (CE) and real-time solution-state NMR spectroscopy.

Quantifying the Heterogeneity of Chemical Structures in Complex Charged Polymers through the Dispersity of Their Distributions of Electrophoretic Mobilities or of Compositions.

The complexity of synthetic and natural polymers used in industrial and medical applications is expanding; thus, it becomes increasingly important to improve and develop methods for their molecular characterization. Free-solution capillary electrophoresis is a robust technique for the separation and characterization of both natural and synthetic complex charged polymers. In the case of polyelectrolytes, free-solution capillary electrophoresis is in the "critical conditions" (CE-CC): it allows their separation by factors other than molar mass for molar masses typically higher than 20000 g/mol.

Cellular Response to Linear and Branched Poly(acrylic acid).

Poly(acrylic acid-co-sodium acrylate) (PNaA) is a pH-responsive polymer with potential in anticancer drug delivery. The cytotoxicity and intracellular effects of 3-arm star, hyperbranched and linear PNaA were investigated with L1210 progenitor leukemia cells and L6 myoblast cells. Free solution capillary electrophoresis demonstrated interactions of PNaA with serum proteins.

Quantification of sugars in breakfast cereals using capillary electrophoresis.

About 80% of the Australian population consumes breakfast cereal (BC) at least five days a week. With high prevalence rates of obesity and other diet-related diseases, improved methods for monitoring sugar levels in breakfast cereals would be useful in nutrition research. The heterogeneity of the complex matrix of BCs can make carbohydrate analysis challenging or necessitate tedious sample preparation leading to potential sugar loss or starch degradation into sugars.

Investigation of photochemical reactions of saccharides during direct ultraviolet absorbance detection in capillary electrophoresis.

Direct UV detection of saccharides in capillary electrophoresis is possible due to a base-catalyzed conversion into UV absorbing substances initiated by the light of the UV detector lamp. In the present study the compounds formed during this reaction were investigated with capillary electrophoresis using an additional UV lamp for online irradiation at a certain distance before the detector resulting in a separation of the conversion products. It was found that for all investigated saccharides (glucose, ribose and sucrose) the major portion of the UV absorption in direct UV detection resulted from one and the same substance.

Real-time monitoring of peptide grafting onto chitosan films using capillary electrophoresis.

Chitosan, being antimicrobial and biocompatible, is attractive as a cell growth substrate. To improve cell attachment, arginine-glycine-aspartic acid-serine (RGDS) peptides were covalently grafted to chitosan films, through the widely used coupling agents 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC-HCl) and N-hydroxysuccinimide (NHS), via the carboxylic acid function of the RGDS molecule. The grafting reaction was monitored, for the first time, in real time using free-solution capillary electrophoresis (CE).

Purity of double hydrophilic block copolymers revealed by capillary electrophoresis in the critical conditions.

Block copolymers enable combining properties of different polymers; double hydrophilic block copolymers are innovative examples. Size-exclusion chromatography (SEC or GPC) has a quasi-monopoly in separation-based characterization methods for polymers, including block copolymers. However, in terms of purity determination (unintended homopolymers present in the copolymers), SEC resolution proves insufficient except for the extreme compositions for which the second block is much larger than the first one.

Ethanol determination using pressure mobilization and free solution capillary electrophoresis by photo-oxidation assisted ultraviolet detection.

Free solution capillary electrophoresis (CE) can separate and quantify carbohydrates using a simple direct UV detection based on a photo-oxidation reaction taking place in the detection window without any labeling. Ethanol interferes with this photo-oxidation reaction. We thus present the first detection and quantification of ethanol using either a simple pressure mobilization set-up or CE.

Understanding and improving direct UV detection of monosaccharides and disaccharides in free solution capillary electrophoresis.

Direct UV detection of carbohydrates in free solution capillary electrophoresis at 270 nm is made possible by a photo-oxidation reaction. Glucose, rhamnose and xylose were shown to have unique UV absorption spectra hypothesizing different UV absorbing intermediates for their respective photo-oxidation. NMR spectroscopy of the photo-oxidation end products proved they consisted of carboxylates and not malondialdehyde as previously theorized and that oxygen thus plays a key role in the photo-oxidation pathway.

Supramolecular organization of protonated aminosilicones in water.

This study deals with the ionically-driven self-assembly of oligomeric aminosilicones, judiciously protonated with a variety of organic acids. Depending on the length of the silicone and the strength of the associated acids, (inverse) water-in-silicone emulsions, small nanoparticles, or catanionic vesicles were prepared and characterized by conventional (TEM) or original (DIC optical microscopy, DOSY NMR) techniques. For chains longer than about 40 units, a specific PEG-based sulfonic acid was synthesized and used to generate a supramolecular block-like copolymer and ensure fast and efficient emulsification.

Separation of chitosan by degree of acetylation using simple free solution capillary electrophoresis.

Chitosan is a biopolymer of increasing significance, as well as a renewable and sustainable material. Its main molecular characteristics are molar mass and degree of acetylation (composition). Precise average degrees of acetylation were measured by quantitative (1)H solution-state NMR spectroscopy.

Separation of poly(acrylic acid) salts according to topology using capillary electrophoresis in the critical conditions.

Branching was detected in polyacrylates synthesised through radical polymerization via solution-state NMR, while inconsistencies have been reported for the determination of the molar mass of hydrophilic polyacrylates using aqueous-phase and organic-phase size-exclusion chromatography. In this work, poly(sodium acrylate)s, PNaAs, of various topologies were separated for the first time using free-solution capillary electrophoresis (CE). Free-solution CE does not separate the PNaAs by their molar mass, similarly to separations by liquid chromatography in the critical conditions, rather by different topologies (linear, star branched, and hyperbranched).