Simultaneous ion chromatographic separation of anions and cations on poly(aspartic acid) functionalized silica

Poly(aspartic acid)-silica (PolyCAT A), originally designed for the cation-exchange chromatography of proteins, is proposed for the simultaneous ion chromatographic separation of inorganic anions and cations. This is possible owing to the zwitterion-exchange properties of this stationary phase, which are attributed to the presence of both protonated aminopropyl and dissociated carboxylic groups in poly(aspartic acid) attached to the silica. The retention of alkali metal (Li+, Na+, K+), alkaline earth metal (Mg2+, Ca2+), ammonium and inorganic anions (Cl-, H2PO4-, Br-, NO2-, I-, IO3-, NO3-, ClO4-, SCN-) was tested in aqueous solutions of sulfuric, perchloric, sulfosalicylic, citric, oxalic, maleic and aspartic acids with conductimetric detection. The effect of eluent pH, together with the concentration and characteristics of the eluting ions, were studied. Under optimum conditions (0.3 mmol dm(-3) H2SO4-0.2 mmol dm(-3) Li2SO4 eluent), the simultaneous separation of three anions (Cl-, H2PO4-, NO3-) and four cations (Na+, K+, Mg2+, Ca2+), on a PolyCAT A column (200 x 4.6 mm id, 5 microm film thickness) was achieved in 9 min.     

Determination of inorganic anions in biological fluids with direct sample injection by electrostatic ion chromatography using zwitterionic micelles in both stationary and mobile phases

A new ion chromatographic (IC) system, which uses zwitterionic (e.g., Zwittergent 3-14) micelles as both stationary and mobile phases, highly useful for the analysis of inorganic anions in biological samples, was developed. The zwitterionic micellar stationary phase (which is obtained by immobilizing the zwitterionic surfactant on surfaces of the reversed-phase ODS) showed high ability to confine the elution bands of the large amount of SO4(2-) and Cl- to narrow zones. As a result, a base-line separation of NO2-, Br- and NO3- from SO4(2-) and Cl- is always achieved. The zwitterionic micellar mobile phase, (which is obtained by dissolving the zwitterionic surfactant with a suppressive electrolytic solution, e.g., aqueous NaHCO3 solution), on the other hand, showed high ability for rapid elution of proteins. The separation column is therefore always being cleaned up even after the protein-containing sample is directly injected. The zwitterionic micelles are also insensitive to conductivity detection, therefore either the suppressed or the non-suppressed conductivity detection method is applicable for detection of the analyte ions. Urine and serum were chosen as the model real samples and were analysed with direct sample injection; the results of successful determination of a number of inorganic anions (SO4(2-), Cl-, NO2-, Br- and NO3-) in both samples have demonstrated the usefulness of this new IC system.     

Novel imidazolium stationary phase for high-performance liquid chromatography

A new imidazolium anion-exchange phase immobilized on silica is synthesized. HPLC separations of common inorganic anions (IO3-, Cl-, NO2-, Br-, NO3-, I-, SCN-) have been performed using a HPLC column (200 mm x 4.6 mm I.D.) packed with this stationary phase, with a phosphate buffer solution as the mobile phase and UV detection at 200 nm. The effects of pH and concentration of eluent on the separation of anions have been studied. Chromatographic parameters are calculated and the results show that the new stationary phase is of significant potential for the analysis of these anions. Successful separations of some ordinary organic anions have also been achieved with the said stationary phase. Meaningfully, organic and inorganic anions can be determined simultaneously and satisfactorily with several neutral compounds using the column. The separation of some organic compounds including hydroxybenzenes, bases and amines by this stationary phase with only water as the eluent has been investigated.     

Determination of inorganic anions by ion chromatography using a graphitized carbon column dynamically coated with cetyltrimethylammonium ions.

The simultaneous determination of inorganic anions by ion chromatography using a dynamically coated graphitized carbon column with cetyltrimethylammonium (CTA) ions was investigated with suppressed conductivity detection. Column preparations with CTA and sodium carbonate-sodium hydrogencarbonate concentration in the eluent were examined to optimize the separation of seven common anions (F-, Cl-, NO2-, Br-, NO3-, HPO(4)2- and SO(4)2-). Calibration curves were linear from 0.5 to 5 micrograms/ml for F-, from 1.0 to 10 micrograms/ml for Cl-, from 1.5 to 15 micrograms/ml for NO2-, from 2.0 to 20 micrograms/ml for Br- and NO3-, from 5.0 to 50 micrograms/ml for HPO(4)2- and from 3.0 to 30 micrograms/ml for SO(4)2- with correlation coefficients (r) of 0.999 or better. The relative standard deviations of peak areas were between 0.3 and 0.9% for 10 repeated measurements. The application of this newly developed method was demonstrated by the determination of inorganic anions in the water for pharmaceutical purposes. Using CTA-Br as the coating agent, a permanently coated ion-exchange column was obtained, which allowed efficient separations of seven anions without adding any coating agent to the eluent.     

Use of zwitterionic micelles in the eluent: a new approach for ion chromatographic (IC) analysis of ions in biological fluids with direct sample injection

The problem of column performance degradation due to irreversible binding of proteins encountered in ion chromatographic (IC) analysis of ions in protein-containing samples was overcome by using zwitterionic micelles (e.g., Zwittergent-3-14) as a portion of the eluent. A zwitterionic micellar eluent showed high ability for solubilization of proteins, and, hence, the protein-containing samples could be analyzed without need for deproteinization. On the other hand, the zwitterionic micelle was insensitive to conductivity but interacted with the analyte ions, due mainly to its unique configuration of charges (namely, the zwitterionic micelle containing both positively and negatively charged groups but carrying no net charge). Using a zwitterionic micellar eluent, the analyte ions could be detected selectively and sensitively, and moreover, the selectivity for the analyte ions was unique. A conventional anion-exchange column conditioned with a Zwittergent-3-14 micellar eluent was applied for the analysis of real biological samples (serum and urine) with direct sample injection. The results of the successful detection of inorganic anions (Cl-, SO4(2-), NO2-, Br-, and NO3-) have demonstrated the usefulness of this new IC approach for the analysis of biological samples.     

Analysis of inorganic anions by electrostatic ion chromatography using zwitterionic/cationic mixed micelles as the stationary phase

The inability to separate fluoride, phosphate and sulfate by electrostatic ion chromatography (EIC) was overcome by using an ODS silica column coated with mixed zwitterionic-cationic surfactants as the stationary phase. The best results were obtained using the zwitterionic surfactant, 3-(N,N-dimethylmyristylammonium)-propanesulfonate (C19H41NO3S), and the cationic surfactant, myristyltrimethylammonium, CH3(CH2)13N+(CH3)3, in a 10:1 molar ratio in the column coating solution. With a dilute solution of sodium tetraborate as the eluent the model analyte anions were completely separated in the following elution order: F, HPO42-, SO42-, Cl-, NO2-, Br-, NO3-. The very early elution of phosphate and sulfate is most unusual and is unique to this system. Detection limits better than 1.1 x 10(-4) mM and linear calibration plots up to 7.0 mM were obtained with a suppressed conductivity system.     

Application of dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium in wall modification for capillary electrophoresis separation of proteins

A zwitterionic surfactant, dodecyldimethyl (2-hydroxy-3-sulfopropyl) ammonium (C12H25N+(CH3)2CH2CHOHCH2SO3-), named dodecyl sulfobetaine (DSB), was used as a novel modifier to coat dynamically capillary walls for capillary electrophoresis separation of basic proteins. The DSB coating suppressed the electroosmotic flow (EOF) in the pH range of 3-12. At high DSB concentration, the EOF was suppressed by more than 8.8 times. The DSB coating also prevented successfully the adsorption of cationic proteins on the capillary wall. Anions, such as Cl-, Br-, I-, SO4(2-), CO3(2-), and ClO4-, could be used as running buffer modifiers to adjust the EOF for better separation of analytes. Using this dynamically coated capillary, a mixture of eight inorganic anions achieved complete separation within 4.2 min with the efficiencies from 24,000 to 1,310,000 plates/m. In the presence of ClO4- as EOF adjustor, the separation of a mixture containing four basic proteins (lysozyme, cytochrome c, alpha-chymotrypsinogen A, and myoglobin) yielded efficiencies of 204,000-896,000 plates/m and recoveries of 88%-98%. Migration time reproducibility of these proteins was less than 0.5% relative standard deviation (RSD) from run to run and less than 3.1% RSD from day to day, showing promising application of this novel modifier in protein separation.     

整体柱离子相互作用色谱快速分析无机阴离子

研究了用硅胶整体柱和直接电导检测的离子相互作用色谱快速分析常见无机阴离子的方法。实验采用氢氧化四丁铵和邻苯二甲酸为淋洗液,讨论了包括淋洗液浓度、流速和pH对分离的影响。当以1.5 mmol/L氢氧化四丁铵和1.1 mmol/L邻苯二甲酸为淋洗液(pH 5.5),流速6 mL/min时,可以在1 min内分离Cl-、NO2-、Br-、NO3-、ClO3-、SO42-和I-7种阴离子。方法的检出限为0.3~1.9 mg/L,峰面积、峰高的相对标准偏差(RSD,n=5)分别为0.4%~2.2%和0.1%~1.5%。将该法用于测定矿泉水和地下水中的阴离子,加标回收率在97.9%~100.3%之间。     

Silver nanoplates: a highly sensitive material toward inorganic anions

This paper demonstrates a simple sensing method to detect inorganic anions by silver nanoplates (edge length of approximately 70 nm and thickness of approximately 2 nm) in aqueous solution. By this method, the solution system containing silver nanoplates shows a high sensitivity on the order of 1 x 10(-6) M in detecting halides, phosphate, and thiocyanate ions in water at room temperature. The sensitivity could be identified by the shift in the surface plasmon resonance (SPR) band in UV-vis spectrum. The selectivity of such a sensing system toward various anions was also studied, and it was found that this sensing system could distinguish individual anions (e.g., Cl-, Br-, I-, H2PO4-, and SCN-) from other anions (e.g., F-, SO42-, CH3COO-, NO3-, and ClO4-) and inorganic cations (e.g., Zn2+, Cd2+, and Cu2+) under the given conditions. The sensing mechanism was also analyzed. It was proposed that the particle surface electron charging, which is mainly determined by the interaction tendency between silver atoms and various inorganic anions in water, is responsible for the shift in the SPR observed. The need for further studies was finally discussed, particularly for systems composed of mixed anions.     

Application of ion chromatography to the determination of inorganic anions in foodstuffs.

A review on the applications of ion chromatography (IC) to the determination of inorganic anions in foodstuffs is presented. The anions were commonly determined in food, i.e., SO3(2-), NO3- and NO2-, and to a lesser extent Cl-, Br-, I-, SO4(2-), IO3-, BrO3- and phosphate, are considered. In comparison with standard methods for the determination of anions in food products, chromatographic methods are rapid, sensitive and precise. They also have the advantage of determining several ions simultaneously. The separation may be achieved by conventional IC, by ion interaction chromatography or by ion exclusion chromatography. IC has also been applied to the determination of Br, I, N and S in foods after oxidation or combustion of samples and conversion into anionic forms.     

Retention of anions on silica-based metalloporphyrin stationary phases.

The silica-based Fe(III)-protoporphyrin and Zn-tetraphenylporphyrin stationary phases were examined for the HPLC separation of anions. The retention of nine common inorganic anions as well as benzoate anion (BA) and its hydroxy analogues (HBA) was examined using tartrate, acetate, and succinate eluents. The retention factors of inorganic anions on the FeProP stationary phase were in the order Cl- < NO3- < ClO4- < I- < SCN- and for organic anions benzoate < p-hydroxybenzoate < m-hydoxybenzoate < o-hydroxybenzoate. The retention factors of organic anions examined for a ZnTPP column were in the order p-HBA < m-HBA < BA < o-HBA.     

离子色谱法测定茶叶中无机阴离子及其用于茶叶的分类

提出了离子色谱法测定茶叶中F-、Cl-、NO2-、Br-、NO3-、H2PO4-、SO42-等无机阴离子的方法。采用Shodex IC SI-52 4E阴离子分离柱进行分离,以3.6mmol.L-1碳酸钠溶液和甲醇以体积比98比2混合所得溶液为淋洗液进行洗脱,从而实现7种阴离子的分离。根据茶叶中分离出的7种阴离子含量的不同,利用聚类分析将16个茶叶样品进行分类。     

Bis-dimethylaminobenzaldehyde Schiff-base cobalt(II) complex as a neutral carrier for a highly selective iodide electrode.

A new solvent polymeric membrane electrode based on N,N'-bis-(dimethylaminobenzaldehyde)-glycine cobalt(II) [Co(II)-BDMABG] as a neutral carrier is described, which displays a preferential potentiometric response to iodide ion and an anti-Hofmeister selectivity sequence in the following order: I- > ClO4- > Sal- > SCN- > NO2- > Br- > NO3- > Cl- > SO3(2-) > SO4(2-). The electrode exhibits a near-Nernstian potential linear range of 9.0 x 10(-7)-1.0 x 10(-1) M with a detection limit of 6.8 x 10(-7) M and a slope of -53.0 mV/decade in pH 2.0 of a phosphate buffer solution at 20 degrees C. The response mechanism is discussed in view of the A.C. impedance technique and the UV spectroscopy technique. The electrode was successfully applied to the determination of iodide in Jialing River and Spring in Jinyun Mountains with satisfactory results.     

Electrostatic ion chromatography using a carboxybetaine-type zwitterionic surfactant as the stationary phase

A carboxybetaine-type zwitterionic stationary phase obtained by immobilizing Mitsubishi Reagent EF-700 (C(8)F(17)SO(2)NHC(3)H(6)N(+) (CH(3))(2)-C(2)H(4)-COO(-)) onto a reversed-phase column was used for chromatographic separation of ions. When aqueous electrolyte solutions having higher pH values (>8) were used as eluents, the model analyte ions (NO(2)(-), H(2)PO(4)(-), Cl(-), Br(-), NO(3)(-), ClO(3)(-), I(-) and SCN(-)) were co-eluted and appeared at the void volume of this HPLC system. However, when aqueous electrolyte solutions having lower pH values (<5.5) were used as eluents, these anions were well retained and separated. Furthermore, when acetate buffers (NaAc/HAc) were used as eluents, plots of log k' (k', retention factor) versus pH of eluents (at constant [NaAc+HAc]), and log k' versus log [NaAc+HAc] (at constant pH), were linear with negative slopes. Breakthrough curves for acid solutions obtained using conductivity detection showed that H(+) ions and their conjugate anions were both retained on the stationary phase and the degree of binding was found to be independent of the acid species used. The degree to which the eluent cation was bound onto the carboxylate functionality of the zwitterion was found to exert a major effect on the retention of analyte anions. A strongly bound cation, such as H(+), reduced electrostatic repulsion effects exerted by the carboxylate functionality on analyte anions, so that they could freely access the quaternary ammonium sites on the zwitterion. It is concluded based on these experimental results that both the charges on the zwitterionic stationary phase make meaningful contributions to the separation of the analyte ions.     

离子色谱法测定火场爆炸残留物中7种阴离子

建立了离子色谱法测定爆炸残留物中F,Cl,NO_2,SO_4,Br,NO_3,PO_47种阴离子的方法。采用抑制电导检测器,以DIONEX Ion Pac~?AS11–HC型阴离子交换柱为分离柱,柱箱温度为40℃,以22 mmol/L KOH溶液为淋洗液,流量为1.20 m L/min。F~–,Cl~–,NO_2~–,SO_4~(2–),Br~–,NO_3~–,PO_4~(3–)在各自范围内均呈良好的线性关系,相关系数均大于0.999,检出限在0.06~0.15 mg/L之间,加标回收率为92.5%~101.3%,测定结果的相对标准偏差为1.86%~2.79%(n=7)。该方法简便、快捷,选择性好,灵敏度高,可满足分析要求。     

不纯流动相对离子法分析无机阴离子的影响(英文)

 采用离子模拟研究了流动相不纯对样品中无机阴离子测定造成的干扰。结果表明 ,在流动相中加入Cl-,使得其他 6种阴离子响应值增加。这主要是由于Cl-加入的同时也带来了相应的阳离子 ,在通过抑制器时可带来等量的H+ ,H+ 伴随着各个阴离子样品一起通过检测器 ,使总的样品离子响应值增加。在 6种阴离子中 ,F-和NO-2 对AS14柱的亲和力和Cl-相近 ,其响应值随Cl-加入量的变化趋势相似 ;Br-,NO-3 ,PO3 -4及SO2 -4因其对柱的亲和力大于Cl-,它们的响应值随Cl-加入量的变化趋势也相同。     

New chromogenic and fluorescent probes for anion detection: formation of a [2 + 2] supramolecular complex on addition of fluoride with positive homotropic cooperativity

Two new chromogenic and fluorescent probes for anions have been designed, synthesized, and characterized. These probes contain multiple hydrogen bonding donors including hydrazine, hydrazone, and hydroxyl functional groups for potential anion interacting sites. Despite the possible flexible structural framework due to the presence of sp3 carbon linkage, X-ray structure analysis of probe 2 displayed an essentially planar conformation in the solid state owing to strong crystal packing interactions comprising a combination of favorable pi-pi stacking effect and hydrogen bonding to cocrystallized CH3OH molecules. Both probes 1 and 2 display orange color in DMSO solution and show fairly weak fluorescence at room temperature. Binding studies revealed that both probes 1 and 2 show noticeable colorimetric and fluorescent responses only to F-, OAc-, and H2PO4- among the nine anions tested (F-, Cl-, Br-, I-, OAc-, H2PO4-, HSO4-, ClO4-, and NO3-). The general trend of the sensitivity to anions follows the order of F- > OAc- > H2PO4- > Cl- > Br- approximately I- approximately HSO4- approximately ClO4- approximately NO3-. A 1:2 (probe to anion) binding stoichiometry was found for probe 1 with OAc- and H2PO4- and probe 2 with F-, OAc-, and H2PO4-. The binding isotherm of probe 1 to F- was found to be complicated with apparent multiple equilibria occurring in solution. The formation of an aggregated supramolecular complex upon addition of fluoride is proposed to rationalize the observed optical responses and is supported by ESI mass spectrometry and pulsed-field gradient NMR spectroscopy. Data analysis suggests that the binding of probe 1 to F- shows positive homotropic cooperativity.     

Anion separation by selective crystallization of metal-organic frameworks

A novel approach for the separation of anions from aqueous mixtures was demonstrated, which involves their selective crystallization with metal-organic frameworks (MOFs) containing urea functional groups. Self-assembly of Zn2+ with the N,N'-bis(m-pyridyl)urea (BPU) linker results in the formation of one-dimensional MOFs including various anions for charge balance, which interact to different extents with the zinc nodes and the urea hydrogen-bonding groups, depending on their coordinating abilities. Thus, Cl-, Br-, I-, and SO4(2-), in the presence of BPU and Zn2+, form MOFs from water, in which the anions coordinate the zinc and are hydrogen-bonded to the urea groups, whereas NO3- and ClO4- anions either do not form MOFs or form water-soluble discrete coordination complexes under the same conditions. X-ray diffraction, FTIR, and elemental analysis of the coordination polymers precipitated from aqueous mixtures containing equivalent amounts of these anions indicated total exclusion of the oxoanions and selective crystallization of the halides in the form of solid solutions with the general composition ZnCl(x)Br(y)I(z).BPU (x + y + z = 2), with an anti-Hofmeister selectivity. The concomitant inclusion of the halides in the same structural frameworks facilitates the rationalization of the observed selectivity on the basis of the diminishing interactions with the zinc and urea acidic centers in the MOFs when going from Cl- to I-, which correlates with decreasing anionic charge density in the same order. The overall crystal packing efficiency of the coordination frameworks, which ultimately determines their solubility, also plays an important role in the anion crystallization selectivity under thermodynamic equilibration.     

Successive non-suppressed ion chromatography of common cations and anions using dual columns with single eluent

A successive non-suppressed ion chromatography (IC) system for the determination of common cations (Na+, K+, Mg2+, Ca2+) and anions (Cl-, Br-, NO3-, SO4(2-)) was developed, using two separation columns and a single eluent. 5-Sulfoisophthalic acid eluent was very suitable for such separations with a commercially available cation-exchange column for the mono- and di-valent cations and with an ODS column coated with cetyltrimethylammonium for the anions. Both cations and anions were detected with conductimetrically high sensitivity without any suppressor. After injecting an aliquot of sample solution, the solvent front from the cation-exchange column, including most of the anionic species, was firstly accumulated into the additional 2 ml accumulation loop for 60 s, while the cation IC was performed. Subsequently, the accumulated fraction was introduced into the anion-exchange column and chromatographed. Relative standard deviations (RSDs) of retention times and conductimetric area responses for common cations were within 6% and within 4%, respectively. The linear relationships between molar concentration and detector response ranged from 0.01 to 1.00 mM with r2 of 0.9994 for Na+, 0.9992 for K+, 0.9993 for Mg2+, and 0.9988 for Ca2+. The successive anion IC through the accumulating process was also quantitative, with 95% recovery or over for each analyte. The linear ranges were between 0.01 and 1.00 mM with r2 of 0.9996 for Cl-, 0.9997 for Br-, 0.9993 for NO3-, and 0.9984 for SO4(2-). The method was applied to the determination of common cations and anions in several mineral waters and a hot spring water.     

基于偶氮水杨醛酰腙的氰根比色检测探针的合成及性能

设计合成了一种基于酚羟基和氨基的酰腙类探针分子, 利用紫外-可见吸收光谱和核磁滴定考察了其对F^-, Cl^-, Br^-, I^-, CH₃COO^-, H₂PO₄^-, HSO₄^-, ClO₄^-, CN^-, SCN^-, SO^2-₄和NO^-₃等阴离子的识别作用. 结果表明, 当加入CN^-离子时主体溶液颜色由无色变为黄色, 而加入其它离子时主体溶液颜色不变, 说明该探针在DMSO/H₂O(体积比5: 5)体系中能选择性裸眼比色检测CN^-. 核磁滴定及质谱数据表明, 该探针与CN^-以1:1化学计量比结合, 该过程通过亲核加成方式完成.