Cationic surface-modified regenerated nanocellulose hydrogel for efficient Cr(VI) remediation.

Because nanocellulose has a large specific surface area and abundant hydroxyl functional groups due to its unique nanomorphology, interest increases as an eco-friendly water treatment material. However, the distinctive properties of nanocellulose, which exists in a dispersion state, strongly hamper its usage in practical water treatment processes. Additionally, nanocellulose shows low performance in removing anionic pollutants because of its anionic characteristics. In an effort to address this challenge, regenerated cellulose (RC) hydrogel was fabricated through cellulose's dissolution and regeneration process using an eco-friendly aqueous solvent system. Subsequently, a crosslinking process was carried out to introduce the cationic functional groups to the RC surface PEI coating (P/RC). As a result, the PEI surface cationization process improved the mechanical rigidity of RC and showed an excellent Cr(VI) removal capacity of 578 mg/g. In addition, the prepared P/RC maintained more than 90% removal efficiency even after seven reuses.

Action spectroscopy of the isolated red Kaede fluorescent protein chromophore.

Incorporation of fluorescent proteins into biochemical systems has revolutionized the field of bioimaging. In a bottom-up approach, understanding the photophysics of fluorescent proteins requires detailed investigations of the light-absorbing chromophore, which can be achieved by studying the chromophore in isolation. This paper reports a photodissociation action spectroscopy study on the deprotonated anion of the red Kaede fluorescent protein chromophore, demonstrating that at least three isomers-assigned to deprotomers-are generated in the gas phase. Deprotomer-selected action spectra are recorded over the S1 ← S0 band using an instrument with differential mobility spectrometry coupled with photodissociation spectroscopy. The spectrum for the principal phenoxide deprotomer spans the 480-660 nm range with a maximum response at ≈610 nm. The imidazolate deprotomer has a blue-shifted action spectrum with a maximum response at ≈545 nm. The action spectra are consistent with excited state coupled-cluster calculations of excitation wavelengths for the deprotomers. A third gas-phase species with a distinct action spectrum is tentatively assigned to an imidazole tautomer of the principal phenoxide deprotomer. This study highlights the need for isomer-selective methods when studying the photophysics of biochromophores possessing several deprotonation sites.

Electrophoretic Determination of Symmetric and Asymmetric Dimethylarginine in Human Blood Plasma with Whole Capillary Sample Injection.

Asymmetric and symmetric dimethylarginines are toxic non-coded amino acids. They are formed by post-translational modifications and play multifunctional roles in some human diseases. Their determination in human blood plasma is performed using capillary electrophoresis with contactless conductivity detection. The separations are performed in a capillary covered with covalently bonded PAMAPTAC polymer, which generates anionic electroosmotic flow and the separation takes place in the counter-current regime. The background electrolyte is a 750 mM aqueous solution of acetic acid with pH 2.45. The plasma samples for analysis are treated by the addition of acetonitrile and injected into the capillary in a large volume, reaching 94.5% of the total volume of the capillary, and subsequently subjected to electrophoretic stacking. The attained LODs are 16 nm for ADMA and 22 nM for SDMA. The electrophoretic resolution of both isomers has a value of 5.3. The developed method is sufficiently sensitive for the determination of plasmatic levels of ADMA and SDMA. The determination does not require derivatization and the individual steps in the electrophoretic stacking are fully automated. The determined plasmatic levels for healthy individuals vary in the range 0.36-0.62 µM for ADMA and 0.32-0.70 µM for SDMA.

Simultaneous capillary electrophoresis of anions and cations in a single injection using an anion exchanger-modified capillary for determination of salivary ions in combination with statistical analyses.

This paper describes the simultaneous capillary electrophoresis (CE) of anions and cations using an anion exchange-modified capillary, which was prepared by chemical coating with a cationic silylating reagent, and its application to saliva analysis. The CE method provides high-throughput (5 min for a single sample injection) analysis by generating a high-velocity electroosmotic flow at pH 3.0-3.5. The detection limits at a signal-to-noise ratio of 3 ranged from 1.2 to 18 µM for anions and 1.0 to 2.7 µM for cations. The relative standard deviations for the migration times and peak areas of analytes (n = 4) ranged from 0.05% to 0.40% and 0.94% to 4.7%, respectively. The CE system was used to analyze 11 common ions in saliva samples collected from long-distance runners and sedentary university students before and after running for a set distance or a set time. Interestingly, the SCN- concentrations decreased in the saliva samples of all 14 athletes and 16 sedentary students after running. Furthermore, when the concentrations of the analyzed ions were compared with that of cortisol as a typical stress marker by multiple regression analysis, SCN- and NO3- in saliva samples from the two subject groups strongly correlated with cortisol levels, as determined by an electrochemiluminescence immunoassay. This study improves our knowledge of both the analytical methodology for CE and statistical methods for identifying common ions that could be used as physical stress markers.

Isolation of a Nitromethane Anion in the Calix-Shaped Inorganic Cage.

A calix-shaped polyoxometalate, [V12O32]4- (V12), stabilizes an anion moiety in its central cavity. This molecule-sized container has the potential to control the reactivity of an anion. The highly-reactive cyanate is smoothly trapped by V12 to form [V12O32(CN)]5-. In the CH3NO2 solution, cyanate abstracts protons from CH3NO2, and the resultant CH2NO2- is stabilized in V12 to form [V12O32(CH2NO2)]5- (V12(CH2NO2)). A crystallographic analysis revealed the double-bond characteristic short bond distance of 1.248 Å between the carbon and nitrogen atoms in the nitromethane anion in V12. 1H and 13C NMR studies showed that the nitromethane anion in V12 must not be exchanged with the nitromethane solvent. Thus, the V12 container restrains the reactivity of anionic species.

The preparation of nano-MIL-101(Fe)@chitosan hybrid sponge and its rapid and efficient adsorption to anionic dyes.

The polymer adsorbents in the sponge form have the porous structure and high elasticity that endow them with good adsorption capacity and recyclability. The immobilization of nano-materials in the sponges can improve their adsorption properties evidently. The nano-MIL-101(Fe)@chitosan(CS) hybrid sponge was prepared by freeze-drying method. Characterization results indicated that rhombic nano-MIL-101(Fe) particles were uniformly dispersed throughout the hybrid sponge. The hybrid sponge showed higher efficiency for the adsorption of anionic dyes compared with the pristine CS sponge. The maximum adsorption capacity of MIL-101(Fe)@CS sponge for Acid Red 94 reached 4518 mg/g and the rapid suction experiments on different dyes showed that the hybrid sponge could be used as a filter for the quick removal of anionic dyes in low concentration solution.

Efficient carbon interlayed magnetic chitosan adsorbent for anionic dye removal: Synthesis, characterization and adsorption study.

The present paper describes the synthesis of a novel magnetic chitosan (CCF), in which the carbon-Fe3O4 core-shell nanoparticles play the role of magnetic part. The structure, property and morphology of the magnetic CCF were characterized by FT-IR, XRD, EDAX, SEM and BET techniques. Its adsorption performance was investigated for the removal of methyl orange from aqueous solutions by varying experimental conditions. The results showed the fast adsorption of methyl orange in wide pH range of 3-11 and the maximum adsorption capacity was found to be 425 mg g-1 at 45 °C. The results of adsorption kinetics indicated that the adsorption mechanism was better described by the pseudo-second-order equation, whereas pore diffusion is the rate-controlling of adsorption kinetics. Furthermore, among different isotherm models, Langmuir and Sips isotherm models fitted well the equilibrium experimental data at different temperatures revealing the surface heterogeneity of the adsorbents. The adsorbent exhibited high adsorption performance, compared to the some other chitosan adsorbents reported in literatures.

Anion Recognition by Neutral and Cationic Iodotriazole Halogen Bonding Scaffolds.

A computational study of the iodide discrimination by different neutral and cationic iodotriazole halogen bonding hosts was carried out by means of Density Functional Theory. The importance of the size of the scaffold was highlighted and its impact observed in the binding energies and intermolecular X···I distances. Larger scaffolds were found to reduce the electronic repulsion and increase the overlap between the halide electron lone pair and the corresponding I-C antibonding orbital, increasing the halogen bonding interactions. Additionally, the planarity plays an important role within the interaction, and can be tuned using hydroxyl to perform intramolecular hydrogen bonds (IMHB) between the scaffold and the halogen atoms. Structures with IMHB exhibit stronger halogen bond interactions, as evidenced by the shorter intramolecular distances, larger electron density values at the bond critical point and more negative binding energies.

Indirect CE-UV detection for the characterization of organic and inorganic ions of a broad mobility and pKa range in engine coolants.

An alternative CE-(indirect ultraviolet) method for the analysis of inorganic and organic anions in ethylene glycol-based engine coolants is presented using a BGE with 4 mM pyromellitic acid and 3.4 mM 1,6-hexamethylene diamine, pH 3. Baseline separation of six inorganic (e.g. nitrite, nitrate, and sulfate) and five organic anions (e.g. acetic and glycolic acid) was achieved. Quantification of 8 out of 11 specified anions was possible in stressed engine coolant samples after simple aqueous dilution. LODs between 0.8 and 15.1 mg/L with RSD values of peak areas between 2.6 and 11.9% were obtained. Some limitations due to matrix effects can be overcome with slight adaptations of the BGE. The flexibility of the method is vital regarding the increasing demands for the composition of engine coolants for pollution reduction.

Immune Enhancement Effects of Codium fragile Anionic Macromolecules Combined with Red Ginseng Extract in Immune-Suppressed Mice.

Codium fragile is an edible seaweed in Asian countries that has been used as a thrombolytic, anticoagulant, antioxidant, anti-inflammatory, and immune-stimulatory agent. Ginseng has also been known to maintain immune homeostasis and to regulate the immune system via enhancing resistance to diseases and microorganisms. In this study, anionic macromolecules extracted from C. fragile (CFAM) were orally administered with red ginseng extract (100 mg/kg body weight) to cyclophosphamide-induced immunosuppressed male BALB/c mice to investigate the immune-enhancing cooperative effect of Codium fragile and red ginseng. Our results showed that supplementing CFAM with red ginseng extract significantly increased spleen index, T- and B-cell proliferation, NK cell activity, and splenic lymphocyte immuneassociated gene expression compared to those with red ginseng alone, even though a high concentration of CFAM with red ginseng decreased immune biomarkers. These results suggest that CFAM can be used as a co-stimulant to enhance health and immunity in immunosuppressed conditions.

Effect of the chemical bond on the electrosorption and desorption of anions during capacitive deionization.

This paper is concerned with the effect of the chemical bond on the electrosorption and desorption of anions during capacitive deionization (CDI). An empirical equation developed firstly based on the experimental data in the electrosorption of Cl-. The empirical equation shows that the electrosorption capacity exhibits a logarithmic relationship with anode potential. Electrosorption of ReO4- and NO3- at different anode potentials were studied and the obtained data used to compare with empirical equation. The empirical equation provided results that were in good agreement with experimental data. According to parameters (A and b) of empirical equation, the chemical bond mainly affected adsorption mechanism and desorption performance. For Cl- with the weaker chemical bond, the main mechanism of electrosorption of Cl- is formation of electrical double layers and the desorption is easier, while for ReO4-, the main adsorption mechanism is chemical bonding and adsorbed anion basically fail to desorb at the equal conditions with Cl-. The revelation of all the CDI performance here would appear to be a useful tool for selection of more suitable electrodes materials to improve adsorption capacity and desorption efficiency of anions.

A three-dimensional printed electromembrane extraction device for capillary electrophoresis.

A concentric electromembrane extraction preconcentration device was designed and fabricated using fused deposition modelling 3D printing. The device consisted of a hemispherical electrode sample vial printed from a filament of conductive polylactic acid (PLA), into which sat a smaller hemispherical 3D printed porous membrane acceptor vial. Application of voltage between a point-electrode placed in the center of 20 µL solution inside the acceptor vial and the electrode vial containing 1 mL of sample, enabled anion migration through the 3D printed porous material into the acceptor solution. Electromembrane extraction was proved using fluorescein for imaging of the extraction process, with preconcentration rates of 0.833 µM/sec at 120 V with close to 95% recovery. The performance of the fabricated porous 3D printed device was evaluated for the preconcentration of anions from water prior to capillary electrophoresis detection. Preconcentration factors ranging between 36-44 were obtained for chloride, nitrate, perchlorate and sulfate, while a lower performance was observed for weaker acids as fluoride and phosphate (3-4). The limit of detection (LOD) was determined to be 0.16 µM, 0.18 µM and 0.18 µM for NO3-, ClO4- and SO42- respectively. The extraction and quantitation of ions from a soil slurry without filtration, namely NO3- and SO42- content was determined to be 0.24 and 0.03 mmol/100 g of soil, respectively which are values in the range of those typically reported in soil samples.

Immune-enhancing effects of anionic macromolecules extracted from Codium fragile on cyclophosphamide-treated mice.

Immune-regulation and homeostasis are critical in cancer therapy and immunomodulatory biomaterials have been used to decrease side effects of immunosuppressant drugs. Anionic macromolecules (CFAMs) were isolated from the seaweed Codium fragile, and its immune-enhancing biological activities were examined in CY-induced immunosuppressed mice. CFAMs improved the splenic lymphocyte proliferation, NK cell activity, and spleen index. The expression of immune-associated genes was highly upregulated in splenic lymphocytes, and gene expression was differently regulated according to mitogens such as T-cell (Con A) and B-cell (LPS) mitogens. Additionally, CFAMs boosted the proliferation, NO production, and phagocytosis of peritoneal macrophages. CFAMs also considerably stimulated immune-associated gene expression in peritoneal macrophages. Moreover, our results showed CFAMs mediated its immune-enhancing effects via the MAPK pathway. These suggested CFAMs can be used as a potent immunomodulatory material under immune-suppressive condition. Furthermore, CFAMs may also be used as a bio-functional and pharmaceutical material for improving human health and immunity.

Combination of capillary electrophoresis and molecular modeling to study the enantiomer affinity pattern between ß-blockers and anionic cyclodextrin derivatives in a methanolic and water background electrolyte.

In order to have deep insights into the mechanisms of enantiomer affinity pattern in both aqueous and non-aqueous systems, an approach combining capillary electrophoresis and molecular modeling was undertaken. A chiral ß-blocker; acebutolol, was enantioseparated in aqueous capillary electrophoresis and non-aqueous capillary electrophoresis using two anionic ß-cyclodextrin derivatives. The enantiomer affinity pattern of acebutolol was found to be opposite when an aqueous background electrolyte was replaced with non-aqueous background electrolyte in the presence of heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin but remained the same in the presence of heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin. Molecular docking of acebutolol into two ß-cyclodextrin derivatives indicated two distinct binding modes called 'up' and 'down' conformations. After structure optimization by molecular dynamics and energy minimization, both enantiomers of acebutolol were preferred to the 'up' conformation with heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin while 'down' conformation with heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin. The further calculation of the complex energy with solvent effect indicated that heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin had higher affinity to S-acebutolol than R-acebutolol in non-aqueous capillary electrophoresis while it showed better binding to R-acebutolol in aqueous capillary electrophoresis. However, the heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin bound better to R-acebutolol in both aqueous and non-aqueous capillary electrophoresis, implying that the binding mode played more important role in chiral separation of heptakis(2,3-di-O-methyl-6-sulfo)-ß-cyclodextrin while the solvent effect had prevailing impact on heptakis(2,3-di-O-acetyl-6-sulfo)-ß-cyclodextrin.

Rapid separation of post-blast explosive residues on glass electrophoresis microchips.

This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection (C4 D) for the separation and detection of inorganic anions in post-blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C4 D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp . The separation of Cl- , NO3- , NO2- , SO42- , ClO4- and ClO3- was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 104 and 1.7 × 105 plates/m. The found limits of detection ranged between 2.5 and 9.5 µmol/L. Last, real samples of post-blast explosive residues were analyzed on the ME-C4 D devices obtaining successfully the determination of Cl- , NO3- and SO42- . The achieved concentration values varied between 12.8-72.5 mg/L for Cl- , 1.7-293.1 mg/L for NO3- and 1.3-201.3 mg/L for SO42- . The data obtained using ME-C4 D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME-C4 D devices emerge as a powerful and portable analytical platform for on-site analysis demonstrating to be a promising tool for the crime scene investigation.

Unexpected separate elution of cation and anion of an ammonium salt in supercritical fluid chromatography.

Amines are frequently used as additives in supercritical fluid chromatography (SFC). They allow eluting basic analytes with reasonable retention times and less distorted peak shapes. Since amines are chemically active compounds, their introduction into SFC mobile phase always raises a question on whether they can react with analytes or mobile phase constituents and, if so, can it affect chromatography separation. Primary and secondary amines are known to react with carbon dioxide, also all amines, being bases, can interact with CO2-alcohol mixtures which are known to be slightly acidic. In this work, we report a case of separate elution of an ammonium salt, salbutamol sulfate, anion and cation in SFC. Retention time of a peak which molecular mass registered by mass-spectrometry in ES(-) mode corresponds to HSO4- differs substantially from the retention time of a peak corresponding to salbutamol [M+H] registered in ES(+) regime. Moreover, sulfate anion retention time depends both on amine additive type and concentration whereas salbutamol retention time doesn't. Similar effect is observed on other columns as well as with other ammonium salts. We suppose that such behavior is caused by the exchange chemical reaction happening between ammonium salt analyte and amine additive. An additive converts a salt into a free base form and turns into a salt form itself. If this hypothesis is true, it might be important to take the possibility of such interactions into account during preparative SFC work since the compound injected might not be equivalent to a compound eluted.

Carbon fiber paper@MgO films: in situ fabrication and high-performance removal capacity for phosphate anions.

Porous magnesium oxide (MgO) films on carbon fiber paper (CF) have been successfully fabricated in a hydrothermal route at different calcination temperatures. The CF@MgO samples (CF@MgO-300, -400, and -500) show different morphologies with the increasing surface area from 3 for CF to 27 m2 g-1 for CF@MgO-400. Among the four investigated samples, the CF@MgO-400 exhibits the highest phosphate removal ability (~ 1230 mg g-1) with promising applications for the large-scale utilization at low cost.

Dispersive liquid-liquid microextraction based on liquid anion exchanger for the direct extraction of inorganic anions.

For the first time, the possibility of the use of liquid anion exchangers in dispersive liquid-liquid microextraction for the direct extraction of some inorganic anions (nitrite, nitrate, and iodide) was evaluated. In this technique, chloroform containing a liquid anion exchanger (trioctylamine) was used as extractant. The mixture of the extractant and disperser solvent (acetonitrile) was injected into the acidic sample solution. The protonated trioctylamine formed a water-insoluble salt with the inorganic anions (analytes). After the phase separation and stripping of the analytes from the extractant, the analytes were determined by liquid chromatography with UV detection. Various parameters affecting the extraction efficiency were investigated. Under the optimum conditions, broad linear dynamic ranges, with determination coefficients (r2) higher than 0.998, and enrichment factors between 94 and 244 were obtained. The limits of detection and quantification were in the range of 0.1-0.5 and 0.4-1.7 µg L-1, respectively. Also, the values of intra- and inter-day relative standard deviations were 3.5-5.8% and 5.5-7.8%, respectively. Various real water samples including sea, tap, river, spring and mineral water were analyzed by the method. The method was sensitive, simple, inexpensive and capable of the simultaneous extraction and determination of the selected inorganic anions.

Development of a low flow-resistive charged nanoporous membrane in a microchip for fast electropreconcentration.

A nanoporous poly-(styrene sulfonate) (poly-SS) membrane was developed for fast and selective ion transport in a microfluidic chip. The poly-SS membrane can be photopolymerized in-situ at arbitrary location of a microchannel, enabling integrated fluidics design in the microfluidic chip. The membrane is characterized by a low hydraulic resistance and a high surface charge to maximize the electroosmotic flow and charge selectivity. The membrane characteristics were investigated by charge-selective electropreconcentration method. Experimental results show membranes with various percentages of poly-SS are able to concentrate anions (fluorescein and TRITC-labeled BSA). The anion-selective electropreconcentration process is stable and 26-times faster than previously reported poly-AMPS (2-acrylamido-2-methyl-1-propanesulfonic acid) based system. The electropreconcentration was also demonstrated to depend on the sample valency and buffer concentration.

Efforts to remove aqueous lithium ion using Octolig® and methylated derivatives.

Aqueous Li+ - containing samples (in DI water or well water) were eluted over Octolig®, a polyethylenediimine covalently attached to a high- surface-area silica gel, and only slight removal, if any, could be claimed. However, when using tetrahydrofuran (THF) as a solvent we quantitatively removed lithium ion with Octolig® or with alkylated Octolig®, demonstrating the efficacy of Octolig® and lack of advantage of a N, N'-dialkylated Octolig®. In addition, the removal of alkali metal ions (lithium, sodium, and potassium) in THF by Octolig® was partially selective: While being quantitative for lithium it was only about 40% for potassium. The study has potential implications for using geothermal brines not only as a heat source, but as a source of lithium as well.