Online anion exchange column preconcentration and high performance liquid chromatographic separation with inductively coupled plasma mass spectrometry detection for mercury speciation analysis

A hyphenated method for mercury speciation analysis by the coupling of high performance liquid chromatography and inductively coupled plasma mass spectrometry with the online strong anion exchange column (SAX) preconcentration was developed. The Hg analytes (Hg⁺, MeHg, EtHg and Hg²⁺) were absorbed on the SAX column preconditioned with sodium 3-mercapto-1-propanesulfonate, and then rapidly eluted (less than 16 s) by 5 μL 3% (v/v) 2-mercaptoethanol. The enrichment factors of 1025 for Hg⁺, 1084 for MeHg, 1108 for EtHg and 1046 for Hg²⁺ were obtained using 6 mL sample in a 1.5-min enrichment procedure. Rapid separation of the four mercurial compounds was achieved within 5 min on a 50-mm C₁₈ column using 0.5% (v/v) 2-mercaptoethanol as the mobile phase. The detection limits for Hg⁺, MeHg, EtHg and Hg²⁺ were 0.015, 0.010, 0.009 and 0.016 ng L⁻¹, each, and the relative standard deviations of peak height and peak area (5 ng L⁻¹ for each Hg species) were all below 5%. Mercury speciation in three freshwater, two drinking water and two seawater samples were then analyzed by the proposed method. MeHg and Hg²⁺ concentrations down to 0.14 and 0.56 ng L⁻¹ were detected in the drinking waters.     

D301R树脂吸附-解吸钼的行为研究

对D301R型阴离子交换树脂吸附-解吸钼的条件进行了研究，采用静态法试验了pH值、钼的浓度等因素对该树脂吸附钼的影响；采用动态法讨论了该树脂对钼的饱和吸附量、解吸剂及其浓度对解吸钼的影响。结果表明在pH2．5，钼的浓度为20g/L时吸附效果最好，树脂对钼的饱和吸附量为1020mg／g，而采用150g/L NaOH溶液解吸钼效果最佳。     

Adsorption of some elements from hydrochloric acid by anion exchange

Anion exchange behavior of 20 anionic chemical species was studied focusing on hydrochloric acid solutions. Elution characteristics for some of these anions were followed by using a basic anion exchange resin. Estimates of distribution coefficients in 10⁻³-9 mol/l acid were obtained by analytical determinations of these elements in column effluent solutions. The adsorption data observed in this medium suggests many applications in analytical separations.     

330阴离子交换树脂对草甘膦的吸附性能

采用静态吸附法研究了330阴离子交换树脂对水中草甘膦的吸附性能,并研究了吸附动力学;测定了溶液的pH值、温度、NaCl含量等因素对330树脂吸附草甘膦的影响.结果表明:330树脂对水中草甘膦的吸附速率快;在pH=2.69时对草甘膦的吸附性能最好;330树脂对草甘膦的吸附是放热、自发的过程,吸附等温线符合Freundli...     

A novel primary amine-based anion exchange membrane adsorber

A novel anion exchange membrane adsorber is presented which shows excellent impurity removal under different buffer conductivities ranging from 2 to 2 7mS/cm. The membrane utilizes a primary amine ligand (polyallylamine) and was designed specifically to bind impurities at high salt concentrations. Studies with DNA, endotoxin, and virus spiked into buffer at varying salt conditions were done, resulting in clearance of >3, 4, and 4 LRV, respectively, with negligible change on increasing salt up to 27 mS/cm conductivities. Verification of virus removal in mAb feedstocks is also shown. The data are compared with other membrane adsorbers and a conventional resin which utilize traditional chemistries to demonstrate improved purification performance with the primary amine ligand. Additional data on scale-up of the membrane adsorber device is discussed. A stacked flat-sheet design was implemented to ensure linear scale-up of performance using bovine serum albumin (BSA) as a model. The linearly scalable device, coupled with the highly effective membrane for virus, DNA, and endotoxin removal, represents a step forward in polishing technology for the purification of monoclonal antibodies and recombinant proteins.     

Anion exchange membrane with viologen moiety as anion exchange groups and generation of photo-induced electrical potential from the membrane

An anion exchange membrane with a viologen moiety was prepared by the reaction of a film of chloromethylated polysulfone and 4,4′-bipyridine. The anion exchange membrane showed a high electrical resistance and a high transport number of anions due to the development of high crosslinking by the diamine. After the membrane had been swollen with ethylene glycol, photo-voltage and photo-current (82 mV, 410 nA at 200 kΩ load, 160 μm thick membrane) were generated from the membrane upon photo-irradiation.     

Selective removal of nitrate by using a novel macroporous acrylic anion exchange resin

An anion exchange resin NDP-5 has been prepared successfully and applied on the selective removal of nitrate from SO₄^2-/ NO₃^- binary co-existence system.The composition and morphology of NDP-5 were confirmed by FT-IR and SEM.The NDP-5 resin exhibits the completely different behavior on the adsorption capacity,adsorption kinetic and the effect of the completing anion in the absence or presence of sulfate,compared to D213.And,the resultants of kinetic are well fitted by the pseudo-first-order and pseudo-second-order models.These results are very important to develop novel resins with great features.     

Utilization of anion exchange resin Spectra/Gel for separation of arsenic from water

Arsenic in drinking water is one of the most challenging health hazards facing mankind today. Arsenic is a naturally occurring carcinogen and creates epidemiological problems through chronic ingestion from drinking water. Arsenic is present in water primarily as As(III) or As(V). Removal of both As(III) and As(V) from water by adsorption on strong base anion-chloride has been studied. Arsenic concentration was measured by Inductively Coupled Argon Plasma (ICP) analysis. The resin was regenerated and the adsorbed arsenic fractions were eluted by using 2 M NaCl. The effect of different parameters that influence adsorption process, such as relative arsenic and resin concentrations, retention time, and pH, were investigated. Results obtained revealed that As(III) was poorly adsorbed, whereas As(V) was successfully retained on the resin. The adsorption process was optimized by using 1 g resin for 16 ppm As(V) at pH 9 for 30 min. The removal efficiency of As(V) was 99.2%.     

Fundamental studies of a new series of anion exchange membranes: membrane preparation and characterization

Chemical cross-linking anion exchange series membranes were prepared from linear engineering plastics poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) by conducting the processes of bromination and amination at both benzyl and aryl positions. Compared with the traditional technologies, the membrane route described in this paper has cancelled the chloromethylation process and thus, given up the use of chloromethyl methyl ether, which has been considered as a potential harmful toxicity material. The ion exchange capacity, water content, membrane potential and transport number of membranes were studied. The results show that the membrane properties are significantly affected by the bromination processes: benzyl-substitution will enhance the ion exchange capacity and water content, while the aryl-substitution will decrease the water content with approximately unchanged ion exchange capacity. By properly balancing them, a series of membranes can be obtained to comply with different industrial requirements, such as diffusional dialysis, electrodialysis, and water splitting processes.     

The kinetic study of specific adsorption of phosphate species on Pt(111) in acidic solutions

The study of the adsorption/desorption mechanism of phosphate anions at Pt(111) in acidic solution of pH 4.3 and 0.8 was performed by the potential step method in order to reveal the kinetics of anion adsorption. The current-time curve due to phosphate adsorption/desorption showed various decay features, being dependent on the potential region. The rate of current decay depended on pH, being faster in a lower pH solution. Specific adsorption processes were analyzed by the Langmuir and Elovich adsorption equations and also in terms of a two-dimensional nucleation-growth mechanism in different adsorption/desorption regions. In the case of adsorption in 0.3M phosphate buffer solution of pH 4.3, random adsorption without interaction following the Langmuir adsorption, takes place at low coverage, while random adsorption with repulsive force was observed at high coverage. In the desorption process, random desorption with repulsive force takes place at high coverage, and the repulsive force disappears where random adsorption without interaction takes place at medium coverage. When the surface coverage becomes further lower, the desorption mechanism changes dramatically into a two-dimensional nucleation-growth type, suggesting that an ordered adsorbate structure is formed after a rapid discharge process of anion adsorption.     

阴离子交换树脂分离-原子荧光法测定色母粒中的镉

采用微波消解溶样,结合离子交换法对色母粒样品进行待测元素的提取及净化处理,利用原子荧光光度计进行镉含量的测定。研究了717型阴离子交换树脂对色母粒样品中镉的吸附及分离条件,解决了样品中铅、铜等元素的干扰问题。方法加标回收率在92.4%～117.4%之间,相对标准偏差小于3.0%。     

Renewable molybdate complexes encapsulated in anion exchange resin for selective and durable removal of phosphate

The existence of many anions in wastewater reduces the removal efficiency of phosphate by adsorbents under realistic conditions. Facing this challenge, the study reports on an insistent and stable composite adsorbent of molybdate complexes Fe-(MoO_x) embedded in a macroporous anion exchange resin (D-201). [Fe(MoO_x)]-D-201 shows 93.7% adsorption capacity (28.3 mg/g) for phosphate even when the molar concentration of coexisting ions is 5 times higher than phosphate. The capacity of adsorbent is maintained more than 84.2% after five regeneration cycles to remove phosphate in the wastewater containing coexisting ions. The ability of highly selective removal of phosphate is maintained during the regeneration cycles explained by the change of the binding of molybdate clusters with phosphate, which is due to the different structures of molybdate clusters depending on various pH. In general, this work puts forward a new idea for the development of phosphorus removal adsorbents for the treatment of wastewater containing coexisting ions.     

Using sequential injection analysis for fast determination of phosphate in coastal waters

A sequential injection analysis system (SIA) is described which is suited for the fast determination of filterable molybdate reactive phosphate (FRP, 0.2 μm) in coastal waters. It processes up to 270 samples per hour with a detection limit (3σ) of 0.05 μM and is used for surface mapping of phosphate in areas with steep concentration gradients like the Wadden Sea. The determination is based on the reaction of phosphate with acidic molybdate to phosphomolybdate, which builds non-fluorescent ion pairs with rhodamine 6G. The remaining rhodamine fluorescence is detected at 550 nm with an excitation at 470 nm. Syringe pump, valve and detector were controlled by a self made python programme, which was optimised for high speed SIA measurements in monitoring applications.     

Interaction between anionic polyelectrolytes and anion exchange membranes and change in membrane properties

Electrodialytic transport properties of anion exchange membranes were measured after formation of anionic polyelectrolyte layers on the membrane surfaces: relative transport number of various anions to chloride ions, current efficiency and apparent diffusion coefficients of neutral molecules. The anionic polyelectrolyte layers were formed by immersing the membrane into an aqueous solution of polycondensation product of sodium naphthalene sulfonate and formaldehyde or polystyrene sulfonic acid.

The change in the relative transport number between anions was remarkable in the anion exchange membrane with high ion exchange capacity by forming the layer. Results were: the relative transport number of sulfate ions to chloride ions decreased and those of nitrate ions to chloride ions, fluoride ions to chloride ions and bromide ions to chloride ions increased compared with the corresponding membrane. Although the apparent diffusion coefficient of neutral molecules suggested clogging of the membrane pores by the polyelectrolyte, anions with higher hydrated ionic diameter were able to permeate through the membrane easily. This means that difference of electrostatic repulsion force against two anions is effective on the change in the relative transport number of anions.     

Flow gradient liquid chromatography using a coated anion exchange microcolumn

Ion chromatography on a 4.0-mm-long (3.0 mm ID) ion exchange column is presented. Using a 10 mM phosphate buffer (pH 2.22) the separation of up to six UV-absorbing anions was obtained using the microcolumn, containing 5 microm RP support (Phenomenex Gemini) coated with the zwitterionic surfactant, (N-dodecyl-N,N-dimethylammonio) undecanoate. The short analytical column facilitated the application of a flow gradient programme over the flow range 0.3-5 mL/min resulting in optimum resolution of nitrite, nitrate, benzoate, iodide, thiocyanate and trichloroacetate in less than 10 min. The effect of both eluent concentration and pH on the retention of six selected anions was investigated, showing a strong pH capacity dependence. The microcolumn was found to exhibit no selectivity towards chloride and so was well suited to the analysis of saline samples. To illustrate this, the rapid analysis of a concentrated iodized table salt sample (20 g/L) was carried out. Following standard addition, a concentration of 3.55 +/- 0.05 microg iodide/g and 1.05 +/- 0.02 microg iodate/g in the solid salt sample was determined.     

Determination of lisinopril using anion exchange chromatography with integrated pulsed amperometric detection

A rapid and practical method for direct detection of lisinopril in anion exchange chromatography(AEC) has been developed with integrated pulsed amperometric detection(IPAD).Dionex AS 18(250 mm×2 mm) and AG 18(50 mm×2 mm) columns and 40 mmol/L NaOH solution were used for separation.Multi-step potential waveform parameters were optimized to maximize the signal-to-noise ratio(S/N).Utilizing the optimized waveform,the repeatability(intra-day) precision and intermediate(inter-day) precision were obtained with relative standard deviation(RSD) of 0.74,0.93,respectively.The limit of quantification(LOQ) and limit of detection(LOD) were found to be 0.37,0.12ng/mL,respectively,with the correlation coefficient of 0.9998 over concentration range 0.01-1μg/mL.The present method was successfully applied to the determination of lisinopril in human plasma.The recoveries of plasma sample spiked by 0.2μg/mL,0.8μg/mL lisinopril were 98.31-103.23%with RSD of 1.41%, 0.61%,respectively.     

Improving anion exchange membranes for DMAFCs by inter-crosslinking CPPO/BPPO blends

New anion exchange membranes are prepared by heat-treating the blend base membranes of chloroacetylated poly(2,6-dimethyl-1,4-phenyleneoxide)(CPPO)/bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO). A partially inter-crosslinked structure can be formed therein via a Friedel–Crafts reaction without adding any crosslinking reagent or catalyst. FT-IR and NMR analyses are used to confirm this inter-crosslinking structure and quantify the crosslinking distribution. Physical properties, such as toughness and thermal stability, are enhanced remarkably due to this heat treatment. Furthermore, the final membranes exhibit a high hydroxyl conductivity (up to 0.032 S cm⁻¹ at 25 °C) and extremely low methanol permeability (1.26–1.04 × 10⁻⁷ cm² s⁻¹), which match the requirements for application in low temperature direct methanol alkaline fuel cells (DMAFCs).     

Preparation and characterization of Type II anion exchange membranes from poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)

To separate hydrophilic anions from hydrophobic ones, Type II PPO-based anion exchange membranes were developed. Different from Type I (with both trimethylbenzylammonium and triethylbenzylammonium groups), Type II has an excellent hydrophobicity modifier as fixed groups: dimethyethanolammonium groups, which were introduced into PPO (poly(2,6-dimethyl-1,4-phenylene oxide)) by following benzyl bromination of PPO and subsequent quaternary amination with a dimethylethanolamine (DMEA) aqueous solution. The membrane's intrinsic properties are dependent on DMEA concentration and amination temperature. The optimum conditions for membrane preparation are as follows: amination temperature 70 °C, time 30–48 h, and DMEA concentration 1:3–1:5 (v/v, DMEA to water). The obtained Type II anion exchange membranes had an IEC of 1.5 mmol/g dry membrane, water content of 30%, and membrane area resistance of 30 Ω cm². The introduced dimethyethanolammonium groups can block hydrated anions from the access to membranes but let hydrophobic anions transport; hence, an effective separation between hydrophilic and hydrophobic anions can be achieved during electro-membrane operation.     

Preparation of magnetic anion exchange resin and their adsorption kinetic behavior of reactive blue

Magnetic anion exchange resin(MD-1) was prepared from quaternization of magnetic copolymeric resin(glycidyl methacrylate -eo-divinylbenzene).For comparison,magnetic resin MD-0 without quaternization and non-magnetic resin(D-1) were also synthesized for the adsorption process.It was found that the adsorption was mainly contributed to the chemical interaction between quaternary ammonium groups and reactive blue RXHC.Due to the smaller size,MD-1 had faster adsorption and desorption kinetics than D-1.Coupled with the advantage of easy separation,the magnetic anion exchange resin was considered to be superior to common anion exchange resin in removal of reactive dye.     

Preparation and application of a novel magnetic anion exchange resin for selective nitrate removal

正A novel magnetic anion exchange resin NDM-1 was prepared through suspension polymerization and then functionalized with ammonolysis and alkylating agents.Its application for selective removal of nitrate was performed in comparison with MIEX~.The results demonstrated that NDM-1 achieved higher efficiency in nitrate removal than MIEX~ did,with or without the existence of competing anion SO_4~(2-) ascribed to its longer alkyl chains on exchange sites.Combined with the advantage of easy separation due toγ-Fe_2O_3 implanted,the magnetic anion exchange resin NDM-1 was considered to be superior to MIEX~ for nitrate removal in practical application.