Understanding the Impact of Key Wine Components on the Use of a Non-Swelling Ion-Exchange Resin for Wine Protein Fining Treatment.

The impact of key classes of compounds found in wine on protein removal by the ion-exchange resin, Macro-Prep® High S, was examined by adsorption isotherm experiments. A model wine system, which contained a prototypical protein Bovine Serum Albumin (BSA), was used. We systematically changed concentrations of individual chemical components to generate and compare adsorption isotherm plots and to quantify adsorption affinity or capacity parameters of Macro-Prep® High S ion-exchange resin. The pH (hydronium ion concentration), ethanol concentration, and prototypical phenolics and polysaccharide compounds are known to impact interactions with proteins and thus could alter the adsorption affinity and capacity of Macro-Prep® High S ion-exchange resin. At low equilibrium protein concentrations (< ~0.3 (g BSA)/L) and at high equilibrium protein concentrations in model wines at various pH, the adsorption behavior followed the Langmuir isotherm, most likely due to the resin acting as a monolayer adsorbent. The resulting range of BSA capacity was between 0.15-0.18 (g BSA)/(g Macro-Prep® High S resin). With the addition of ethanol, catechin, caffeic acid, and polysaccharides, the protein adsorption behavior was observed to differ at higher equilibrium protein concentrations (> ~0.3 (g BSA)/L), likely as a result of Macro-Prep® acting as an unrestricted multilayer adsorbent at these conditions. These data can be used to inform the design and scale-up of ion-exchange columns for removing proteins from wines.

A Direct Probe of the Hydrogen Bond Network in Aqueous Glycerol Aerosols.

The properties of aerosols are of paramount importance in atmospheric chemistry and human health. The hydrogen bond network of glycerol-water aerosols generated from an aqueous solution with different mixing ratios is probed directly with X-ray photoelectron spectroscopy. The carbon and oxygen X-ray spectra reveal contributions from gas and condensed phase components of the aerosol. It is shown that water suppresses glycerol evaporation up to a critical mixing ratio. A dielectric analysis using terahertz spectroscopy coupled with infrared spectroscopy of the bulk solutions provides a picture of the microscopic heterogeneity prevalent in the hydrogen bond network when combined with the photoelectron spectroscopy analysis. The hydrogen bond network is composed of three intertwined regions. At low concentrations, glycerol molecules are surrounded by water forming a solvated water network. Adding more glycerol leads to a confined water network, maximizing at 22 mol %, beyond which the aerosol resembles bulk glycerol. This microscopic view of hydrogen bonding networks holds promise in probing evaporation, diffusion dynamics, and reactivity in aqueous aerosols.

Novel fluorene-based fluorescent probe with excellent stability for selective detection of SCN- and its applications in paper-based sensing and bioimaging.

SCN- is one of the most important anions in metabolic processes. However, the investigation of SCN- in living systems is restricted by the lack of stable functional molecular tools. Herein, the first fluorene-based polymer fluorescent probe V1 was synthesized through rational design. Compared with small molecule fluorescent probes, V1 exhibited excellent fluorescence stability in bovine serum albumin (BSA) solution. Furthermore, the V1-based paper sensor was highly selective toward SCN- in aqueous solution. Significantly, these merits of the probe V1 enable the detection of SCN- in different living cell lines and zebrafish.

A graphene oxide-based fluorescent sensor for recognition of glutamate in aqueous solutions and bovine serum.

A novel fluorescence probe based on graphene-aminofluorescein (GAF) for sensing glutamate is prepared by modifying graphene oxide (GO) with 5-aminofluorescein (AF), and shows high sensitivity and selectivity. The strong fluorescence of the GAF probe is quenched in the presence of glutamate, and the quenching exhibits a good linear relationship with the glutamate concentration within the range of 1-45 mg/L. In bovine serum, the accurate quantitation of glutamate is possible within the range of 6 mg/L to 30 mg/L. At the pH of 3.32 (close to the isoelectric point of glutamate), GAF can selectively detect glutamate in preference to other amino acids. The high sensitivity and specificity of this sensor enable a new method for the detection of glutamate in aqueous solutions and serums.

Fractal theory and controllable preparation of centimeter level silver nanowire arrays and their application in melamine detection as SERS substrates.

Silver nanowire arrays as surface-enhanced Raman scattering (SERS) substrates were prepared by a solid-state ionics method under the direct current electric field (DCEF) and used to rapidly detect melamine in aqueous solutions. The arrangement density and surface roughness of the prepared silver nanowire arrays are significantly different upon a change in the impressed current intensity. The growth mechanism of silver nanowire arrays was associated with the apical growth advantage and the irregular electrode interface. When the current intensity was 4 µA and 10 µA, the fractal dimension of silver nanowire arrays was 1.66 and 1.49, the diameters of nanowires ranged from 90 to 130 nm and 90 to 170 nm, and many densely arranged and regularly arranged silver nanoparticles lie in the prepared nanowire arrays, respectively. The result shows that there were more silver nanostructures and surface roughness under 4 µA DCEF. The Raman signal intensity of melamine molecule shows that the prepared SERS substrate exhibited a high sensitivity. The proposed method allow us detect melamine with a limit of 10-15 mol/L and 10-12 mol/L, which are lower than the safety limit estimated by the US food and Drug Administration. With its facile material synthesis, simple detection procedure and low detection concentration, this silver nanowire arrays with high surface roughness indicates a strong potential detection technique in the field of food safety.

Magnetic solid-phase extraction and determination of ultra-trace amounts of antimony in aqueous solutions using maghemite nanoparticles.

A magnetic solid-phase extraction method was developed using maghemite as an efficient sorbent for the separation and preconcentration of antimony prior to its determination by ET-AAS. Maghemite was synthesized through a simple method and characterized by XRD, FT-IR and SEM. Various factors affecting maghemite synthesis, separation and preconcentration of antimony such as desorption solvent type, concentration and volume, desorption temperature and time, sample pH, amount of sorbent, and extraction temperature and time were optimized. The effects of interfering ions were also investigated. Under optimized conditions, the method exhibited good linearity (r2 > 0.9960). The sorption capacity and enrichment factor (EF) of the method were 37.5 mg g-1 and 242, respectively. The limit of detection (LOD) was 0.03 ng mL-1. The intraday, interday, and batch-to-batch relative standard deviations (%RSDs) were quite reasonable. The proposed method was applied to various real samples and the relative recoveries found were between 95.8 and 104.0 %.

A Comparison of QM/MM Simulations with and without the Drude Oscillator Model Based on Hydration Free Energies of Simple Solutes.

Maintaining a proper balance between specific intermolecular interactions and non-specific solvent interactions is of critical importance in molecular simulations, especially when predicting binding affinities or reaction rates in the condensed phase. The most rigorous metric for characterizing solvent affinity are solvation free energies, which correspond to a transfer from the gas phase into solution. Due to the drastic change of the electrostatic environment during this process, it is also a stringent test of polarization response in the model. Here, we employ both the CHARMM fixed charge and polarizable force fields to predict hydration free energies of twelve simple solutes. The resulting classical ensembles are then reweighted to obtain QM/MM hydration free energies using a variety of QM methods, including MP2, Hartree⁻Fock, density functional methods (BLYP, B3LYP, M06-2X) and semi-empirical methods (OM2 and AM1 ). Our simulations test the compatibility of quantum-mechanical methods with molecular-mechanical water models and solute Lennard⁻Jones parameters. In all cases, the resulting QM/MM hydration free energies were inferior to purely classical results, with the QM/MM Drude force field predictions being only marginally better than the QM/MM fixed charge results. In addition, the QM/MM results for different quantum methods are highly divergent, with almost inverted trends for polarizable and fixed charge water models. While this does not necessarily imply deficiencies in the QM models themselves, it underscores the need to develop consistent and balanced QM/MM interactions. Both the QM and the MM component of a QM/MM simulation have to match, in order to avoid artifacts due to biased solute⁻solvent interactions. Finally, we discuss strategies to improve the convergence and efficiency of multi-scale free energy simulations by automatically adapting the molecular-mechanics force field to the target quantum method.

A New Environmentally-Friendly Colorimetric Probe for Formaldehyde Gas Detection under Real Conditions.

A new environmentally-friendly, simple, selective and sensitive probe for detecting formaldehyde, based on naturally-occurring compounds, through either colorimetric or fluorescence changes, is described. The probe is able to detect formaldehyde in both solution and the gas phase with limits of detection of 0.24 mM and 0.7 ppm, respectively. The probe has been tested to study formaldehyde emission in contaminated real atmospheres. The supported probe is easy to use and to dispose, and is safe and suitable as an individual chemodosimeter.

Homeopathic Dilutions, Hahnemann Principles, and the Solvent Issue: Must We Address Ethanol as a "Homeopathic" or a "Chemical" Issue?

INTRODUCTION: Homeopathic remedies usually contain a significant amount of ethanol as a co-solvent with water, a pharmaceutical formulation that may raise some concern when remedies are tested in vitro or in laboratory animals, due to the assessed toxicity of ethanol on cell cultures and organisms. The amount of alcohol in a homeopathic remedy is adjusted following the different homeopathic pharmacopoeias but it is rarely below 30% v/v, which is a molar mass established to meet both Hahnemann's traditional heritage and the hypothetical role of ethanol in "imprinting" water, through the formation of nanobubbles, with the homeopathic activity of the remedy. AIMS: This article aims at discussing the role of ethanol in homeopathic dilutions and how its chemical nature should affect the experimental approach in homeopathy. ISSUES UNDER DEBATE: While the content of ethanol in a homeopathic remedy should be as low as 20% v/v, which is a molar fraction able to catalyze the formation of nanobubbles in a dynamized alcohol-water dilution, this amount raises concern about ethanol toxicology in the experimental research with laboratory animals or in vitro. Several authors diluted 1:100 ethanol 30% v/v from their tested homeopathic dilutions with distilled water to prevent the cytotoxic effect of the alcohol, but in doing so, they probably reduced the ability of ethanol (now 0.3% v/v) to induce the formation of nanobubbles, thus probably affecting the homeopathic property of the same dilution. This may generate concerns about how to manage an experimental setting, to meet both the "chemical" nature of ethanol and its role in "homeopathy," an issue that is discussed in the article. CONCLUSION: Any author working with homeopathic dilutions containing a molar fraction of ethanol higher than 20% should take into account the fact that ethanol is cytotoxic and may be a catalyst to the formation of nanobubbles, and so should adjust the experimental approach accordingly.

NMR diffusometry data sampling optimization for mixture analysis.

NMR diffusometry is a powerful but challenging method to analyze complex mixture. Each component diffuses differently, from the faster small species to the slower large species, corresponding to different signal attenuation. However, the method is highly sensitive to the quality of the acquired data and the performance of the processing used to resolve multiexponential signals influences. Adapting the signal decay sampling to the mixture composition is one way to improve the precision of the measure. In this work, we propose a prediction tool, based on the calculation of the Cramér-Rao lower bound to minimize the variance of diffusion coefficient estimation in order to determine the optimal number of diffusion gradient steps, the best diffusion gradient sampling (among linear, exponential, quadratic and sigmoidal ones) and the optimal maximum diffusion factor. The tool was validated experimentally on a unimer/micelle solution of sodium dodecyl sulfate and on Caelyx®, a commercial liposomal preparation containing a mixture of pegylated-liposomes and sucrose.

A reusable adsorbent polyethylenimine/polyvinyl chloride crosslinked fiber for Pd(II) recovery from acidic solutions.

In this study, a mixture of polyethylenimine (PEI) and polyvinyl chloride (PVC) was reacted at 80 °C for 6 h to synthesize crosslinked PEI/PVC polymer solution, which was injected to produce the PEI/PVC-crosslinked fiber (PEI/PVC-CF). PEI/PVC-CF was investigated as an adsorbent to remove and recover Pd(II) from acidic solutions. In order to examine the adsorption characteristics and usability of PEI/PVC-CF for Pd(II) recycling, several experiments such as isotherm, kinetics, desorption and reuse were conducted. The adsorption isotherms were fitted using the Langmuir and Freundlich models, respectively. The maximum adsorption capacity was estimated as 146.03 mg/g according to the Langmuir model. The kinetic experiments demonstrated that adsorbent reaches adsorption equilibrium within 60 min for initial Pd(II) concentrations of 25-100 mg/L. After adsorption, Pd(II) on PEI/PVC-CF was easily desorbed using acidified thiourea solution, and the desorption efficiency increased with the thiourea concentration. It was also demonstrated that PEI/PVC-CF can be used repeatedly for at least five cycles without reduction in adsorption capacity.

Transition from non-Fickian to Fickian longitudinal transport through 3-D rough fractures: Scale-(in)sensitivity and roughness dependence.

Understanding transport in rough fractures from non-Fickian to Fickian regimes and the prediction of non-Fickian transport is critical for the development of new transport theories and many practical applications. Through computational experiments that fall within the macrodispersion regime, we first simulated and analyzed solute transport through synthetic rough fractures with stationary geometrical properties (i.e., fracture roughness σb/〈b〉 and correlation length λ, where b refers to aperture with its standard deviation σb and arithmetic mean 〈b〉) across increasing fracture longitudinal transport domain length L, with L/λ ranging from 2.5 to 50. The results were used to determine how solute transport behavior evolves with increasing scale in the longitudinal direction. Moreover, a set of correlated fractures with aperture fields following normal and log-normal distributions was created to further identify and quantify the dependence of non-Fickian transport on roughness. We found that although persistent intermittent velocity structures were present, the breakthrough curves (BTCs) and residence time distributions showed diminishing early arrival and tailing, features of non-Fickian transport, with increasing longitudinal L/λ, ultimately converging to a Fickian transport regime given σb/〈b〉 remained constant. Inverse analysis of the experimental BTCs with the advection-dispersion equation (ADE) model showed that the dispersion coefficient (D) was non-trivially scale-dependent. Simulation results for rough fractures with varying σb/〈b〉 and L/λ indicated that the ratio of fluid velocity to transport velocity fitted to the ADE model depends on σb/〈b〉 and L/λ. The continuous time random walk (CTRW) performed much better across all transport scales, and resulted in scale-independent fitted parameters, i.e., ß in the memory function. The fitted ß is proportional to σb/〈b〉but is insensitive to L/λ. Therefore, bulk longitudinal solute transport across the pre-asymptotic and asymptotic regimes can be estimated based on the CTRW model parameterized by measurable fracture physical properties.

Rapid analysis of tetracycline hydrochloride solution by attenuated total reflection terahertz time-domain spectroscopy.

Despite numerous methods for the detection of antibiotic residues, they are usually destructive and require tedious pre-treatment. Terahertz time-domain spectroscopy (THz-TDS) is an emerging technology that has advantages for analyzing chemical and biological compounds since THz waves are very sensitive to the molecular vibrational modes. Here we incorporated attenuated total reflection technique into the THz-TDS and demonstrated that this technology (ATR THz-TDS) allowed to determine the complex refractive indices of tetracycline hydrochloride (TCH) solutions with high accuracy and could be used to predict their concentrations. Our results from the simple linear regression models indicated that the complex refractive index exhibited a monotonic decrease with an increase in the TCH concentration. This study will provide new knowledge about the concentration determination of a liquid sample that couldn't be elucidated with the conventional THz-TDS technologies.

Effect of hydrogen peroxide on improving the heat stability of whey protein isolate solutions.

Whey protein isolate (WPI) solutions (12.8%w/w protein) were treated with varying concentrations of H2O2 in the range of 0-0.144 H2O2 to protein ratios (HTPR) by the addition of the required quantity of H2O2 and deionized water. The samples were analyzed for heat stability, rheological properties, denaturation level of ß-lactoglobulin (ß-LG) and α-lactalbumin (α-LA). The samples treated with H2O2 concentration >0.072 (HTPR) showed significant improvement in the heat stability, and decreased whey protein denaturation and aggregation. The WPI solution treated with H2O2 (>0.072 HTPR) remained in the liquid state after heat treatment at 120°C, whereas the control samples formed gel upon heat treatment. Detailed analysis of these samples suggested that the improvement in the heat stability of H2O2 treated WPI solution was attributed to the significant reduction in the sulfhydryl-disulfide interchange reaction during denaturation of ß-LG and α-LA.

Applicability of refractometry for fast routine checking of hospital preparations.

Quality control of hospital pharmacy formulations is of the utmost importance to ensure constant quality and to avoid potential mistakes before administration to the patient. In this study we investigated the applicability of refractometry as a fast, inexpensive and easy-to-use quality control measurement. Refractive indices (RI) of a multitude of different hospital formulations with varying concentrations of active compound were measured. The samples consisted of a number of binary aqueous solutions (one compound in water), complex aqueous solutions (multiple compounds in water or in a constant matrix), two suspensions and one emulsion. For all these formulations, linear regression analysis was performed, quality control limits determined and accuracy and repeatability were checked. Subsequently, actual hospital pharmacy samples were analyzed to check whether they were within the specified limits. For both binary and complex aqueous formulations, repeatability was good and a linear correlation for all samples could be observed on condition that the concentration of the active compound was sufficiently high. The refractometer was not sensitive enough for solutions of folic acid and levothyroxine, which had too low a concentration of active compound. Due to lack of homogeneity and light scattering, emulsions and suspensions do not seem suitable for quality control by refractometry. A mathematical equation was generated to predict the refractive index of an aqueous solution containing clonidine HCl as active compound. Values calculated from the equation were compared with measured values and deviations of all samples were found to be lower than 1.3%. In order to use refractometry in a hospital pharmacy for quality control of multicomponent samples, additional intermediate measurements would be required, to overcome the fact that refractometry is not compound specific. In conclusion, we found that refractometry could potentially be useful for daily, fast quality measurements of relatively concentrated binary and more complex aqueous solutions in the hospital pharmacy.

Estimation of minimum miscibility pressure (MMP) of CO2 and liquid n-alkane systems using an improved MRI technique.

Minimum miscible pressure (MMP) of gas and oil system is a key parameter for the injection system design of CO2 miscible flooding. Some industrial standard approaches such as the experiment using a rising bubble apparatus (RBA), the slim tube tests (STT), the pressure-density diagram (PDD), etc. have been applied for decades to determine the MMP of gas and oil. Some theoretical or experiential calculations of the MMP were also applied to the gas-oil miscible system. In the present work, an improved technique based on our previous research for the estimation of the MMP by using magnetic resonance imaging (MRI) was proposed. This technique was then applied to the CO2 and n-alkane binary and ternary systems to observe the mixing procedure and to study the miscibility. MRI signal intensities, which represent the proton concentration of n-alkane in both the hydrocarbon rich phase and the CO2 rich phase, were plotted as a reference for determining the MMP. The accuracy of the MMP obtained by using this improved technique was enhanced comparing with the data obtained from our previous works. The results also show good agreement with other established techniques (such as the STT) in previous published works. It demonstrates increases of MMPs as the temperature rise from 20 °C to 37.8 °C. The MMPs of CO2 and n-alkane systems are also found to be proportional to the carbon number in the range of C10 to C14.

Salt-Induced Universal Slowing Down of the Short-Time Self-Diffusion of a Globular Protein in Aqueous Solution.

The short-time self-diffusion D of the globular model protein bovine serum albumin in aqueous (D2O) solutions has been measured comprehensively as a function of the protein and trivalent salt (YCl3) concentration, noted cp and cs, respectively. We observe that D follows a universal master curve D(cs,cp) = D(cs = 0,cp) g(cs/cp), where D(cs = 0,cp) is the diffusion coefficient in the absence of salt and g(cs/cp) is a scalar function solely depending on the ratio of the salt and protein concentration. This observation is consistent with a universal scaling of the bonding probability in a picture of cluster formation of patchy particles. The finding corroborates the predictive power of the description of proteins as colloids with distinct attractive ion-activated surface patches.

Ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography.

The use of ammonium fluoride as a mobile phase additive in aqueous normal phase chromatography with silica hydride-based stationary phases and mass spectrometry detection is evaluated. Retention times, peak shape, efficiency and peak intensity are compared to the more standard additives formic acid and ammonium formate. The test solutes were NAD, 3-hydroxyglutaric acid, α-ketoglutaric acid, p-aminohippuric acid, AMP, ATP, aconitic acid, threonine, N-acetyl carnitine, and 3-methyladipic acid. The column parameters are assessed in both the positive and negative ion detection modes. Ammonium fluoride is potentially an aggressive mobile phase additive that could have detrimental effects on column lifetime. Column reproducibility is measured and the effects of switching between different additives are also tested.

Application of surface enhanced Raman scattering to the solution based detection of a popular legal high, 5,6-methylenedioxy-2-aminoindane (MDAI).

The ever increasing numbers and users of designer drugs means that analytical techniques have to evolve constantly to facilitate their identification and detection. We report that surface enhanced Raman scattering (SERS) offers a relatively fast and inexpensive method for the detection of MDAI at low concentrations. Careful optimisation of the silver sol, and salt concentrations was undertaken to ensure the SERS analysis was both reproducible and sensitive. The optimised system demonstrated acceptable peak variations of less than 15% RSD and resulted in a detection limit of just 8 ppm (5.4 × 10(-5) M).

A Time-Encoded Technique for fibre-based hyperspectral broadband stimulated Raman microscopy.

Raman sensing and microscopy are among the most specific optical technologies to identify the chemical compounds of unknown samples, and to enable label-free biomedical imaging. Here we present a method for stimulated Raman scattering spectroscopy and imaging with a time-encoded (TICO) Raman concept. We use continuous wave, rapidly wavelength-swept probe lasers and combine them with a short-duty-cycle actively modulated pump laser. Hence, we achieve high stimulated Raman gain signal levels, while still benefitting from the narrow linewidth and low noise of continuous wave operation. Our all-fibre TICO-Raman setup uses a Fourier domain mode-locked laser source to achieve a unique combination of high speed, broad spectral coverage (750-3,150 cm(-1)) and high resolution (0.5 cm(-1)). The Raman information is directly encoded and acquired in time. We demonstrate quantitative chemical analysis of a solvent mixture and hyperspectral Raman microscopy with molecular contrast of plant cells.