Ion-exchange Mode Research Articles

Comparison of Pharmacokinetic Profiles of 14 Major Bioactive Components in Normal and Arthritic Model Rats after Oral Administration of Angelicae pubescentis Radix by UPLC-MS/MS.

An ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established to simultaneously determine 14 compounds of Angelicae pubescentis Radix (APR) in normal and arthritis rat plasma in which chloramphenicol and daidzein were used as the internal standards. After protein precipitation with acetonitrile, separation was carried out on a Thermo Hypersil GOLD C18 column using gradient elution with 0.1% formic acid aqueous and acetonitrile consisting as the mobile phase at a flowing rate of 0.3 mL/min. A Thermo TSQ QUANTIS triple quadrupole mass spectrometer was used to detect 14 compounds in positive/negative ion exchange mode and this study was the first to investigate the pharmacokinetic changes of the active compounds in rats under the pathological state of arthritis. The method was verified and the results showed that the intra- and interday precision, accuracy, matrix effect, and extraction recovery were all acceptable, and the analytes were stable under different storage conditions. In addition, the pharmacokinetic behaviors of the 14 compounds were significantly different in model rats compared with normal rats. This indicated that the pharmacokinetic behavior of drugs will vary with the pathological state of the body, which suggested that individualized and reasonable drug administration plans should be formulated for different pathological states in clinical practice. This study provided a scientific basis and data support for better understanding the pharmacodynamic substance basis and clinical application of APR against arthritis.

Comparative Evaluation of the Adsorption Performance of Citric Acid-Treated Peels of Trapa natans and Citrullus lanatus for Cationic Dyes Degradation from Water

Various chemicals were explored in chemical combinations with two selected agrowastes in order to optimize, enhance, and improve their biosorption potential for the optimal and effective eradication of noxious, carcinogenic, and malignant cationic and basic dyes from wastewater. In this project, environmentally safe, economic, inexpensive, and widely available peels of Trapa natans (TP) and Citrullus lanatus (CP) were collected, dried, and pretreated with citric acid, revealing promising results. FT-IR and SEM characterizations of chemically changed biosorbents (C-TP and C-CP) have evidenced the presence of more secondary adsorption sites on their surfaces. These acid-modified biosorbents were employed to eliminate the hazardous and toxic basic dyes such as Rhodamine B (RAD) and Brilliant Green Dye (BLG) in batch mode processing. The Langmuir model was best fitted to equilibrium experimental data as compared to Freundlich and Temkin isothermal mathematical models with Qmax of 15.63 and 27.55 mg/g for RAD using C-TP and C-CP, respectively, whereas, for BLG on C-TP and C-CP, it was 128 and 189 mg/g, respectively. Therefore, the mechanism is related to chelation and ion exchange modes between adsorbate molecules and adsorbent surfaces, leading to homogeneous and monolayer adsorption and following pseudo-2nd-order kinetics in the best way. Thermodynamic parameters such as ΔG0, ΔS0, ΔH0, and ΔE0 are determined statistically for the adsorption performance of both novel chemically mutant biosorbents, which reflect that biosorption mechanisms are exothermic as well as spontaneous.

Biosorption of Uranium from aqueous solution by green microalga Chlorella sorokiniana

Uranium and its compounds are radioactive and toxic, as well as highly polluting and damaging the environment. Novel uranium adsorbents with high biosorption capacity that are both eco-friendly and cost-effective are continuously being researched. The non-living biomass of the fresh water green microalga Chlorella sorokiniana was used to study the biosorption of uranium from aqueous solution. The biosorption of uranium from aqueous solutions onto the biomass of microalga C. sorokiniana was investigated in batch studies. The results showed that the optimal pH for uranium biosorption onto C. sorokiniana was 2.5. Uranium biosorption occurred quickly, with an equilibrium time of 90 min. The kinetics followed a pseudo-second-order rate equation, and the biosorption process fit the Langmuir isotherm model well, with a maximum monolayer adsorption capacity of 188.7 mg/g. The linear plot of the DKR model revealed that the mean free energy E = 14.8 kJ/mol, confirming chemisorption adsorption with ion exchange mode. The morphology of the algal biomass was investigated using a scanning electron microscope and energy dispersive X-ray spectroscopy. The FTIR spectroscopy analysis demonstrated that functional groups (carboxyl, amino, and hydroxyl) on the algal surface could contribute to the uranium biosorption process, which involves ion exchange and uranium absorption, and coordination mechanisms. Thermodynamic simulations indicated that the uranium biosorption process was exothermic (ΔH = −19.5562 kJ/mol) and spontaneous at lower temperatures. The current study revealed that C. sorokiniana non-living biomass could be an efficient, rapid, low-cost, and convenient method of removing uranium from aqueous solution.

Fast and Versatile Chromatography Process Design and Operation Optimization with the Aid of Artificial Intelligence

Preparative and process chromatography is a versatile unit operation for the capture, purification, and polishing of a broad variety of molecules, especially very similar and complex compounds such as sugars, isomers, enantiomers, diastereomers, plant extracts, and metal ions such as rare earth elements. Another steadily growing field of application is biochromatography, with a diversity of complex compounds such as peptides, proteins, mAbs, fragments, VLPs, and even mRNA vaccines. Aside from molecular diversity, separation mechanisms range from selective affinity ligands, hydrophobic interaction, ion exchange, and mixed modes. Biochromatography is utilized on a scale of a few kilograms to 100,000 tons annually at about 20 to 250 cm in column diameter. Hence, a versatile and fast tool is needed for process design as well as operation optimization and process control. Existing process modeling approaches have the obstacle of sophisticated laboratory scale experimental setups for model parameter determination and model validation. For a broader application in daily project work, the approach has to be faster and require less effort for non-chromatography experts. Through the extensive advances in the field of artificial intelligence, new methods have emerged to address this need. This paper proposes an artificial neural network-based approach which enables the identification of competitive Langmuir-isotherm parameters of arbitrary three-component mixtures on a previously specified column. This is realized by training an ANN with simulated chromatograms varying in isotherm parameters. In contrast to traditional parameter estimation techniques, the estimation time is reduced to milliseconds, and the need for expert or prior knowledge to obtain feasible estimates is reduced.

A docosyl-terminated polyamine amphiphile-bonded stationary phase for multimodal separations in liquid chromatography

A convenient synthetic approach to a linear alkyl-polyamine amphiphilic chromatographic selector was proposed. Successive immobilization of the amphiphile onto silica gel afforded a multimodal stationary phase for high-performance liquid chromatography (HPLC). The as-prepared silica material was studied comparatively with a conventional octadecyl (C18) and an amide-embedded C18 stationary phase. The new uniform docosyl-triamine tandem was featured by an enhanced shape selectivity towards geometric isomers, and a low silanol activity towards alkaline solutes. The presence of multiple amino groups rendered the new adsorbent operable in different modes, such as hydrophilic interaction and ion-exchange modes. The satisfactory performance of the said stationary phase in separating different classes of analytes, including polycyclic aromatic hydrocarbons, flavonoids, tricyclic antidepressants, calcium channel blockers, aromatic acids, inorganic anions, nucleosides and estrogens, revealed its great potential and high adaptability for multipurpose LC utility.

Research progress of microextraction by packed sorbent and its application in microvolume sample extraction

微萃取技术是分析化学领域发展迅速,且已经得到广泛应用的样品前处理技术。填充吸附剂微萃取(MEPS)是一种微量固相萃取技术,使用微量的吸附剂填充于微量注射器,通过反复抽推方式使样品多次流经吸附剂以完成样品吸附萃取过程,萃取后的样品可直接用于色谱分析。典型的MEPS萃取设备包括MEPS注射器和MEPS吸附床(BIN)。MEPS优化的主要因素为MEPS处理过程的参数,包括样品流速、样品量与样品萃取循环次数,吸附剂及淋洗、洗脱溶剂的种类和体积,还需要考虑样品基质对MEPS性能的影响和样品残留和重复使用问题。MEPS中最重要的部分是吸附剂,主要有商品化的MEPS吸附剂,包括硅基的Silica、C18、C8等,碳材料的Hypercarb和聚苯乙烯聚合物类的SDVB、HDVB吸附剂等。研究用的吸附剂包括分子印迹材料、限进分子印迹材料、碳基材料、导电聚合物类材料、改性硅基材料及共价-有机骨架材料等。MEPS结合多种分析仪器已经成功应用于从不同基质中提取单一或多种分析物,所涵盖基质包括生物样品(尿液、唾液、血浆或血液)、河流水体或生活污水以及几种食品和饮料。MEPS处理复杂生物基质样品时,通常需要稀释样品、除蛋白质等预处理。MEPS具有需要样品体积小、操作快速等特点,在生物基质样品分析中有望得到更广泛的使用。在环境样品中,该技术可与现场便携仪器联用,未来将有望在现场进行快速检测,并于易分解样品等方面发挥作用。

A four-dimensional separation approach by offline 2D-LC/IM-TOF-MS in combination with database-driven computational peak annotation facilitating the in-depth characterization of the multicomponents from Atractylodis Macrocephalae Rhizoma (Atractylodes macrocephala)

Plant metabolites represent complex chemical system, which renders it difficult to clarify the chemical composition by conventional liquid chromatography/mass spectrometry (LC/MS) due to the limited selectivity and peak capacity. The rhizomes of Atractylodes macrocephala have been utilized as a traditional Chinese medicine Atractylodis Macrocephalae Rhizoma (Bai-Zhu), and have been reported containing multiple categories of plant metabolites. Targeting the multicomponents from A. macrocephala, an integral approach by offline two-dimensional liquid chromatography/ion mobility quadrupole time-of-flight mass spectrometry (2D-LC/IM-QTOF-MS) was established and validated. By configuring an XBridge Amide column of Hydrophilic Interaction Chromatography and an Atlantis Premier BEH C18AX column of mixed ion exchange and reversed-phase modes, the established 2D-LC/IM-QTOF-MS system showed high orthogonality up to 0.91. Dimension-enhanced, data-independent high-definition MSE (HDMSE) in the positive ESI mode was conducted on a Vion IM-QTOF mass spectrometer, and its hyphenation to offline 2D-LC could enable the four-dimensional separation (each dimension in 2D-LC, IM, and MS). Particularly, HDMSE facilitated the acquisition of high-definition MS1 and MS2 spectra. In-house library-driven computational peak annotation by the bioinformatics platform UNIFI could efficiently process and annotate the HDMSE data for the structural elucidation. By integrating reference compounds comparison, we could identify or tentatively characterize 251 components from A. macrocephala (including 115 sesquiterpenoids, 90 polyacetylenes, 11 flavonoids, 9 benzoquinones, 12 coumarins, and 14 others), which indicated large improvement in identifying those minor plant components, compared with the conventional LC/MS approach. Conclusively, offline 2D-LC/IM-QTOF-HDMSE in combination with computational data interpretation proves to be powerful facilitating the in-depth multicomponent characterization of herbal medicine.

Preparation of an aspartame and N-isopropyl acrylamide copolymer functionalized stationary phase with multi-mode and chiral separation abilities

A novel multi-mode and chiral separation stationary phase co-modified with copolymer composed of N-isopropyl acrylamide (NIPAM) and aspartame was synthesized by atom transfer radical polymerization (ATRP) reaction. The synthetic material was evaluated using thermogravimetric analysis (TGA), Fourier transform infrared spectrometry (FT-IR) and elemental analysis (EA). Analytes including hydrophobic, hydrophilic, alkaline and acidic compounds were separated well using the prepared stationary phase named Sil-PPAM-NIPAM. Besides, the separation of chiral compounds proved that the developed column also has the potential of chiral separation ability. In summary, the prepared column possesses excellent hydrophilic interaction, ion exchange, reversed-phase and chiral separation modes during the separation of complex and chiral compounds.

Ion exchange and ion exclusion chromatographic characterization of wines using conductivity detection

High performance ion chromatography system employing ion exchange and ion exclusion modes was used for the separation and quantitative analysis of tartarate, malate, citrate, lactate, chloride, nitrate, phosphate, sulfate, lithium, sodium, potassium, magnesium, and calcium in 15 wines originated worldwide. All anions were measured by means of conductivity detection. Analytical figures of merit were assessed and reported for all analyzed ions. In addition, the classic physicochemical properties of wines, i.e. color, acidity and density, were determined. Correlations between measured variables were evaluated and discussed. The proposed procedure is exceptionally simple and requires only regular instrumentation; nevertheless, it provides possibility for fast, straightforward and sensitive quantification of aforementioned ions. Sample preparation required only filtration and dilution where necessary.

Electrochemical properties and sodium ion diffusion in Na3V(PO4)2

Understanding the material process and the mechanism behind during battery operation is essential to discover or identify new electrode for the sodium ion batteries. Using first-principles calculations, we systematically investigated the fundamental physical properties, electrochemical activity as well as sodium ion diffusion of the new discovered cathode material, Na3V(PO4)2. The results identified that the Na+ ion on Na2 sites is preferentially extracted from the host, which is responsible for the electrochemical redox process, instead of that on Na1 sites, proposed experimentally. The predicted cell voltage delivers two ‘plateaus’ with average voltage profile at ~ 3.1 and ~ 3.9 V vs. Na+/Na, corresponding to the V3+/V4+ and V4+/V5+ redox process, respectively, reproducing the experimental observations. Actually, the redox activity of V ions is accompanied with the formation of small polaron as manifested by the magnetic moments and spin density analysis. Furthermore, the fade of the reversible capacity is attributed to the considerable large volume variation (>5%) during the charging-discharging cycling, due to the flexibility of yavapaiite-type layers. The sodium ion diffusion is accomplished through the step-wise ion-exchange mode, in which the Na+ ions originated from both Na1 and Na2 sites migrate, progressively and independently, along the a axis between the yavapaiite-type layers, creating a zigzag Na2→Na1→Na2 trajectory. Meanwhile, the activation energy is calculated to be reasonable for facile ion diffusion. In addition, the fundamental electronic structures on different charging stages are examined thoughtfully. Our results not only provide a valuable insight on the electronic properties, electrochemical behavior of sodium disintercalation process and diffusion mechanism of Na3V(PO4)2, but also inevitably highlight the clues to suppress the large volume variation upon charge/discharge process, and then to improve the cycling capacity.

Extraction and determination of pyridinium ionic liquid cations in environmental water samples by using strong cation exchange solid phase extraction and ion chromatography

ABSTRACTThis paper presents a novel analytical method for the determination of pyridinium ionic liquid cations in environmental water samples by ion chromatography coupled with solid phase extraction. The water samples were purified and enriched by a sulphonic acid extraction column, and then the impurities were washed with 10 mL water – 20% (v/v) acetonitrile solution and the analytes eluted with 0.5 mol L−1 phosphoric acid – sodium dihydrogen phosphate buffer solution – 55% methanol. The eluted analytes were determined by ion chromatography with 3.0 mmol L−1 methane sulphonic acid – 8% acetonitrile as the mobile phase and direct conductivity detection. Three pyridinium cations were completely separated in 20 min and the retention mechanism basically conforms to the ion exchange mode. The newly developed method has been successfully applied to the analysis of pyridinium cations in spiked environmental water samples, which provided satisfactory recoveries in the range of 98.8% to 100.0% with the relative standard deviations less than 2.8%. The concentration of 0.004 to 0.01 mg L−1 in water samples can be preconcentrated by this method. The method is accurate, reliable, simple and practical. This research provides a new reference for detecting ionic liquid cations in environmental water samples and studying the environmental risk assessment of ionic liquids.

Control of the NO–NH3 SCR Behavior of Cu-ZSM-5 by Variation of the Electronic State of Copper

The effect of NH4OH/Cu2+ in a copper-acetate solution on the properties of ion-exchanged Cu-ZSM-5 catalysts in the selective catalytic reduction of NO by NH3 (NO–NH3 SCR) has been studied. The temperature programmed desorption of ammonia (NH3-TPR) on Cu-ZSM-5 and the ammonia adsorption–desorption dynamics at 75–300 °C were studied to identify and quantify the nature of acid sites and ammonia desorption heat of Cu-ZSM-5. The Cu-ZSM-5 catalysts containing Cu-structures with extra-lattice oxygen were active in the low-temperature SCR, whereas those with isolated Cu2+ ions were active in the high-temperature SCR. It was shown that Cu-structures with extra-lattice oxygen were generated during the ion exchange of H-ZSM-5 with a water-ammonia solution of copper-acetate where the NH4OH/Cu2+ ratio was in the range of 6–15. Isolated Cu2+ ions were produced in the ion-exchange mode with the ammonia-free solution.

Preparation of Cationic Mixed-Mode Acrylamide-Based Monolithic Stationary Phases for Capillary Electrochromatography

A series of amphiphilic macroporous mixed-mode acrylamide-based continuous beds bearing positively charged quaternary ammonium groups is synthesized for capillary electrochromatography (CEC) under variation of the concentration of the cationic monomer in the polymerization mixture. Positively charged mixed-mode monolithic stationary phases are synthesized in pre-treated fused silica capillaries of 100 µm I.D via single step free radical copolymerization of cyclodextrin-solubilized N-tert-butylacrylamide, a hydrophilic crosslinker (piperazine diacrylamide), a hydrophilic neutral monomer (methacrylamide), and a positively charged monomer ([2-(methacryloyloxy)ethyl]trimethyl ammonium methyl sulfate) in aqueous solution containing the lyotropic salt ammonium sulfate as a pore-forming agent. The synthesized monolithic stationary phases contain hydrophobic, hydrophilic, and charged functionalities. They can be employed for the CEC separations of different classes of neutral and charged solutes (with varied polarity) in the reversed-phase mode, in the normal-phase mode, in the ion-exchange mode, in a mixed-mode, or in the hydrophilic interaction liquid chromatography (HILIC) mode. The influence of the concentration of the cationic monomer in the polymerization mixture on retention factor, electroosmotic mobility, and methylene selectivity (αmeth) is studied under isocratic conditions for alkylphenones in the reversed-phase mode by capillary electrochromatography (CEC). Scanning electron microscopy (SEM) micrographs demonstrate that the morphology of the synthesized monoliths (i.e., the domain size) is strongly influenced by the variation of the concentration of the cationic monomer in the polymerization mixture.

Composite modification mechanism of cationic modifier to amphoteric modified kaolin and its effects on surface characteristics

In this study, the changes of S DC curves (sum amount of dodecyl trimethyl ammonium cation and Ca2+/2 adsorbed on dodecyl dimethyl betaine-modified kaolin under different dodecyl trimethyl ammonium cation molar fractions) were analyzed to reveal the modification mechanism of cationic modifier (dodecyl trimethyl ammonium bromide) on amphoteric modified kaolin (kaolin modified by dodecyl dimethyl betaine). In addition, total organic carbon content and surface characteristics of different modified kaolins were analyzed using X-ray diffraction, specific surface area calculation, Fourier transform infrared spectroscopy, thermogravimetry, and scanning electron microscope. Results showed that: (1) “S DC” curves of compositely modified kaolin with dodecyl dimethyl betaine-modified ratios of 15, 30 and 60 % started to rise (appeared hydrophobic binding) at dodecyl trimethyl ammonium bromide-modified ratios of 16.80, 7.63, and 0.68 % (the critical point for different modification mechanisms), respectively. (2) Total organic carbon content of modified kaolins under different modification mechanisms showed hydrophobic modification mode > ion exchange and hydrophobic binding coexisting mode > ion exchange mode. Interlayer spacing showed no significant change under different modification modes. Specific surface area decreased slowly with enhanced hydrophobic modification mode. Fourier transform infrared spectroscopy and thermogravimetry results showed the modification effects of both dodecyl dimethyl betaine and dodecyl trimethyl ammonium bromide modification on kaolin surfaces. Scanning electron microscope results presented that the number of lamellar structures increased on clay surfaces with enhanced hydrophobic modification mode.

Separation of pegylated recombinant proteins and isoforms on CIM ion exchangers.

Protein pegylation is a process of covalent attachment of a polyethylene glycol (PEG) group to the protein tertiary structure that can "mask" the agent from the immune system and also increases the hydrodynamic size of the agent. Usually the pegylation prolongs the protein stability in the organism due to reduced renal clearance and provides superior water solubility to hydrophobic molecules. The mono-pegylated form of protein is usually prefered for medical applications. Different conditions with different PEG reagents have to be tested to find optimal pegylation procedure with specific protein. The goal of this study was to prepare screening method for separation of random mono-pegylated protein. Cytochrome C and beta lactoglobulin were pegylated with four reagents and a complete screening of several chromatographic monoliths in ion exchange mode with different buffers was performed to optimaly separate each mono-pegylated protein. The screening method was developed that produces optimal separation of target pegylated protein on CIM monoliths. Because of short chromatographic run time, CIM monoliths are perfect candidates to test alot of parameters. The results obtained show that each protein has its own unique separation parameters (pH, ionexchange ligand, buffer type). Two biopharmaceuticals were isolated using protocol: super human leptin antagonist (SHLA) was purified from inclusion bodies and mono-pegylated super mouse leptin antagonist (SMLA) from pegylated mixture. During study it was observed that the convective interaction media (CIM) monoliths additionally discriminate between protein isoforms pegylated on different sites in 3D structure of the protein.

Influence of the state of Zn species over Zn-ZSM-5/ZSM-11 on the coupling effects of cofeeding n-butane with methanol

Combination of the exothermic methanol aromatization with the endothermic n-butane aromatization provides a good way to meet the increasing demand for aromatics. Here, a series of Zn-ZSM-5/ZSM-11 catalysts were prepared with different introduction methods. The influence of location and state of Zn species on the coupling effects of cofeeding n-butane with methanol were investigated in detail. UV–vis, H2-TPR and XPS spectra were applied to reveal the state of the Zn species on different catalysts. Quantitative results of NH3-TPD and Pyridine-FTIR were provided to compare the acidity changes of the catalyst after Zn loading. Physical mixing method led to high portion of bulk ZnO particles outside the channel which could promote the formation of C2C4 light alkane in cofeeding reaction. Ion exchange and impregnation modes were beneficial for the formation of ZnOZn bridging species in the micropore channel. ZnOZn bridging species was found to increase the promoting effect of cofeeding n-butane with methanol on aromatics selectivity.

Synergistic integration of catalysis and ion-exchange for highly selective reduction of nitrate into N2

An integrated process synergistically combining the advantages of catalysis and ion-exchange is demonstrated for the selective and complete degradation of NO3− from contaminated water. To realize this process, PdCu catalysts were supported on an ion-exchange resin. The functional resin captures NO3− in an ion-exchange mode, whereas the concentrated NO3− in the resin is fully reduced by the supported PdCu in a catalytic regeneration mode. The complete conversion of the captured NO3− indicates that the solid-state diffusion of NO3− within the resin is possible through consecutive ion-hopping. Catalytic resin regeneration under H2/CO2 (1/1, v/v) was found to reduce NO3− to N2 selectively without the formation of the toxic byproduct NH4+. The complete suppression of the NH4+ formation (∼100% N2 selectivity) has never been reported previously. It is well known that the accumulation of OH− ions generated during the NO3− reduction significantly enhances the formation of NH4+. We propose that OH− ions generated on the catalyst surface are rapidly captured by the ion-exchange sites of the resin, thus minimizing the detrimental interaction between OH− and the catalyst surface. The ion-exchange/catalytic regeneration cycle could be repeated up to five times without a loss of the NO3− ion-exchange capacity or catalytic regenerability.

Poly(N-vinylimidazole/ethylene glycol dimethacrylate) for the purification and isolation of phenolic acids

In this study we report the novel polymeric resin poly(N-vinyl imidazole/ethylene glycol dimethacrylate) for the purification and isolation of phenolic acids. The monomer to crosslinker ratio and the porogen composition were optimized for isolating phenolic acids diluted in acetonitrile at normal phase chromatography conditions, first. Acetonitrile serves as polar, aprotic solvent, dissolving phenolic acids but not interrupting interactions with the stationary phase due to the approved Hansen solubility parameters. The optimized resin demonstrated high loading capacities and adsorption abilities particularly for phenolic acids in both, acetonitrile and aqueous solutions. The adsorption behavior of aqueous standards can be attributed to ion exchange effects due to electrostatic interactions between protonated imidazole residues and deprotonated phenolic acids. Furthermore, adsorption experiments and subsequent curve fittings provide information of maximum loading capacities of single standards according to the Langmuir adsorption model. Recovery studies of the optimized polymer in the normal-phase and ion-exchange mode illustrate the powerful isolation properties for phenolic acids and are comparable or even better than typical, commercially available solid phase extraction materials. In order to prove the applicability, a highly complex extract of rosemary leaves was purified by poly(N-vinyl imidazole/ethylene glycol dimethacrylate) and the isolated compounds were identified using UHPLC–qTOF-MS.

Preparation of a weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography stationary phase for protein separation using click chemistry.

In this study, 3-diethylamino-1-propyne was covalently bonded to the azide-silica by a click reaction to obtain a novel dual-function mixed-mode chromatography stationary phase for protein separation with a ligand containing tertiary amine and two ethyl groups capable of electrostatic and hydrophobic interaction functionalities, which can display hydrophobic interaction chromatography character in a high-salt-concentration mobile phase and weak anion exchange character in a low-salt-concentration mobile phase employed for protein separation. As a result, it can be employed to separate proteins with weak anion exchange and hydrophobic interaction modes, respectively. The resolution and selectivity of the stationary phase were evaluated in both hydrophobic interaction and ion exchange modes with standard proteins, respectively, which can be comparable to that of conventional weak anion exchange and hydrophobic interaction chromatography columns. Therefore, the synthesized weak anion exchange/hydrophobic interaction dual-function mixed-mode chromatography column can be used to replace two corresponding conventional weak anion exchange and hydrophobic interaction chromatography columns to separate proteins. Based on this mixed-mode chromatography stationary phase, a new off-line two-dimensional liquid chromatography technology using only a single dual-function mixed-mode chromatography column was developed. Nine kinds of tested proteins can be separated completely using the developed method within 2.0 h.

Cu-substituted ZSM-5 catalyst: Controlling of DeNOx reactivity via ion-exchange mode with copper–ammonia solution

The regularities of sorption and stabilization of Cu2+ ions in Cu–ZSM-5 catalysts prepared via the ion-exchange have been studied. The copper sorption by H–, Na–, and NH4–ZSM-5 from aqueous and ammonia solutions of copper salt had a good approximation as the Langmuir mould of a monolayer adsorption. At ideal ion-exchange condition, only the isolated copper ions located in the zeolite ion-exchange position are formed. Observation of other Cu structures with extra-lattice oxygen is a result of the hydrolysis of hexaaquacopper(II) complex and its polycondensation reactions. They exist as (1) dimer and copper-oxide structures with chain-like and square-planar coordination of extra-lattice oxygen ligands, which are located inside zeolite channels, and (2) oxide clusters and CuO nanoparticles dispersed on the zeolite crystallite surface.The RedOx properties and DeNOx reactivity in selective catalytic reduction of nitrogen oxide by propane of copper-substituted ZSM-5 have been compared. The dynamics of DeNOx reactivity correlates with the growth in the number of the isolated Cu2+ ions and the Cu structures with extra-lattice oxygen, which are formed during the ion exchange of H–ZSM-5 with water–ammonia solutions of copper acetate with NH4OH/Cu2+ close to 6 (pH∼10.5). On the other hand, reactivity decreases with an increase in the content of copper-oxide clusters on the external surface of zeolite, which are observed in the ion-exchanged Cu–ZSM-5 at NH4OH/Cu2+ below 6. Besides, the Cu2+ ions stabilized during the ion-exchange mode with strong-alkaline ammonia–copper solution (NH4OH/Cu2+=30) are less reducible in H2-TPR experiment compared with catalysts produced from ammonia-free and weak-ammonia solution of copper acetate, probably due to the low copper loading, stabilization of isolated Cu2+Oh ions with large distance between each other, decoration of copper ions by a thin silica/alumina layer or formation of Cu-silicates.