Mixed-bed Ion-exchange Column Research Articles

Prompt digestion and HPIC separation of rare earth elements in surrogate post-detonation debris material with detection by ICP-MS and gamma spectroscopy

Prompt analysis of fission products and rare earth elements (REE)s in post-detonation nuclear debris is critical for nuclear forensic analysis. In this work the compatibility of ammonium biflouoride fusion and microwave digestion in combination with high pressure ion chromatography (HPIC) separation was examined for the analysis of REEs. The refractory geological materials USGS G-2, QLO-1a, AGV-2 and BHVO-2 were used as surrogate post-detonation debris. The HPIC separation used a mixed bed ion exchange column with a gradient elution consisting of oxalic acid and diglycolic acid mobile phases. Quantitative recovery for seven REEs was achieved using the in-line HPIC-ICP-MS. An off-line HPIC method was also developed to separate U, Pu, and REE fission products. Collected fractions were analyzed by ICP-MS or gamma ray spectroscopy. The offline HPIC separation with detection of short-lived fission products with gamma ray spectroscopy had detection limits 5–20,000 times lower than quadrupole ICP-MS for stable REEs.

Strategy for high-throughput identification of protein complexes by array-based multi-dimensional liquid chromatography-mass spectrometry

Comprehensive elucidation of the composition of multiprotein complexes in model organisms is essential to understand conserved biological systems, but large-scale mapping physical association networks is still challenging due to limited throughput of present methods. In this work, a strategy coupling array-based online two-dimensional liquid chromatography (array-based 2D-LC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was demonstrated for high throughput and in-depth identification of protein complexes from cultured human HeLa cell extracts. Mixed-bed ion-exchange column was employed as the first dimensional (1stD) separating mode and an array consisting of eight reversed phase columns was developed as the second dimensional (2ndD) mode. Taking advantage of array parallel strategy, this online system showed an 8-fold increase in throughput. After array-based online 2D-LC separation, altogether 256 × 2ndD fractions were collected for further LC-MS/MS analysis. Public databases of protein-protein interaction (PPI) and co-elution curves identified by LC-MS were applied to reconstruct the protein complexes. A rigorous inspection was operated by cataloging the protein complexes into chromatographic fractions to minimize the number of false positives. As result, a total number of 4,436 proteins were identified and 26,092 elution curves were graphed. A network consisting of 47,745 PPIs was established among 2,201 proteins and presented 1,530 putative protein complexes with high confidence. Most of the identified PPIs were linked to diverse biological processes and may reveal further disease mechanism and therapeutic strategy.

Determination of the lanthanides, uranium and plutonium by means of on-line high-pressure ion chromatography coupled with sector field inductively coupled plasma-mass spectrometry to characterize nuclear samples

High-pressure ion chromatography (HPIC) was coupled with sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) to separate plutonium (Pu), uranium (U), neodymium (Nd) and gadolinium (Gd) nuclides from isobaric nuclides and to quantify them with high sensitivity. In this study, mixed bed ion exchange columns CG5A and CS5A were used, from which Pu and U were eluted first using 1 M nitric acid. The lanthanides were then separated using a gradient of 0.1–0.15 M oxalic acid with the pH adjusted to 4.5. The HPIC-SF-ICP-MS method was validated using different sample matrices, i.e. spent nuclear fuel and soil. The method was found to be repeatable and gave rise to transient signals suitable for quantification of nuclide-specific concentrations using external calibration. In terms of accuracy, the HPIC-SF-ICP-MS measurement results were in good agreement with those obtained using thermal ionization mass spectrometry (TIMS). Finally, the method provides an improvement in sample throughput (≤60 minutes per sample) and reduces exposure of the operator to radiation compared to off-line gravitational chromatography followed by TIMS.

Tandem Cation/Anion Exchange SPE Cartridge Method for Sample Desalting for HPLC Analysis of Soluble Dietary Fiber: Development and Inter-laboratory Validation.

In HPLC analyses of soluble dietary fiber, desalting processes using open, mixed-bed ion-exchange columns are time-consuming and labor-intensive. We developed and validated a simple desalting method using tandem cation/anion exchange SPE cartridges. We found that combining Bond Elut Jr SCX (upstream) and Bond Elut PSA (downstream) cartridges provided adequate desalting of test solutions. The developed method was then validated in an inter-laboratory study. Five test samples were prepared by mixing food matrixes with purified soluble dietary fiber and treated to generate solutions to test the desalting process. These solutions were then analyzed by eight different laboratories. The results demonstrated that the developed method is simple and reliable for desalting samples containing 140 to 945 mg/100 mL of soluble dietary fiber in preparation for HPLC analysis of soluble dietary fiber.

Critical point analysis and biocide treatment in a microbiologically contaminated water purification system of a power plant

Many industries use ultrapure water (UPW) for their operation. In spite of purification efforts, microbial contaminations are the major cause of manufacturing problems in these systems. In our experiments, the water purification system of a power plant was investigated: the microbiologically critical points of the ultrapure water purification system were located by checking the number and diversity of bacteria to determine the optimum operational unit for chemical intervention: the most contaminated site was the mixed-bed ion-exchange resin containing unit. Biocides were tested against bacteria previously isolated from the same system; effect of biocides was checked also in laboratory model systems, and based on the results, a biocide treatment was carried out in the mixed-bed ion-exchange resin columns of the working power plant. Kathon WT was the most effective from the studied chemicals, being effective already in low concentration against most studied microorganisms. In case of the handling of the mixed-bed ion-exchange resin, 8-h treatment with 25 ppm biocide concentration was effective. Following the treatment, the quality of the produced UPW met the standards (specific electric conductivity was < 1.0 × 10−3 µS cm−1 at 25 °C) and water production capacity increased; moreover, the run-down time of the mixed-bed ion-exchange resin significantly grew.

Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography.

A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na(+)), potassium (K(+)), ammonium (NH4 (+)), chloride (Cl(-)) and nitrate (NO3 (-)) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples.

Simultaneous Analysis of Inorganic Monovalent Anions/Cations Using Mixed-Bed Single-Column Ion Chromatography

The ion-exchange properties of a new mixed-bed ion-exchange column Scherzo SSC18 (Imtakt, USA) were investigated. This mixed-mode column is packed with two types of 3 µm spherical silica particles having either octadecyl- and strong cation-exchange functional groups or octadecyl- and strong anion-exchange functional groups. The regularities of the retention of alkali metal cations and inorganic anions were studied with diluted acids (sulfuric, perchloric to phosphoric, nitric, oxalic and citric acids) as eluents and direct conductivity for the detection. Eluent concentration, column temperature and organic solvent addition effects were investigated. The separations were achieved on the basis of ion-exchange interactions introduced by the strong anion and strong cation-exchange functionalities of the stationary phase; meanwhile, contribution of hydrophobic interactions was also evident for the hydrophobic iodide and thiocyanate. The simultaneous separation of 12 inorganic anions and cations in 20 min was obtained under isocratic conditions with 1 mM oxalic acid as eluent. The applicability of developed method to the determination of chloride, sodium, potassium as well as nitrite, nitrate and ammonium in soil extracts was demonstrated with good potential for nitrogen speciation studies.

Establishment and application of integrated platform for proteome quantification

To improve the accuracy, throughput and automation of proteome quantification analysis, an integrated platform including a microflow mixed-bed ion exchange column, a hydrophilic immobilized enzymatic reactor (hIMER) and nanoRPLC-electrospray ionization (ESI)-MS/MS system was established. Online separation and digestion of dimethylated proteins, followed by peptide separation, identification and quantification can be realized automat ically by this platform. High and light dimethyl-labeled (H/L) proteins with the mass ratio of 1:1 were used to evaluate the quantification performance of the platform. The results showed that the dimethyl labeling efficiency at protein level was 90%. The incomplete digestion resulting from 10 min online digestion by the hIMER column and the non-specific adsorption of protein digests on the column had little adverse effect on the accuracy of protein quantification results. The mean value of H/L (mass ratio) of all the quantified proteins was 1.01. This platform was finally applied to analyze the different protein expression levels of two mice hepatocarcinoma ascites cell lines with high and low lymph node metastasis rates (Hca-F and Hca-P cell lines). Finally 15 up-regulated and 12 down-regulated proteins (Hca-F/Hca-P) were successfully obtained. All these results demonstrated that the integrated platform can be used for proteome quantification with the advantages of high accuracy and high throughput.

Protein pre-fractionation with a mixed-bed ion exchange column in 3D LC–MS/MS proteome analysis

The fractionation of complex samples at the protein level prior to shotgun proteomics analysis is an efficient means to more comprehensive analysis of samples. A mixed-bed ion-exchange (IEX) column, packed with both weak anion exchange (WAX) and weak cation exchange (WCX) materials, was used for the first dimensional separation of complex samples at the protein level using volatile solvents. The peptides from digestion of each fraction were then identified by 2D SCX-RP-LC–MS/MS. We applied this 3D strategy to mouse mammary tumor 4T1 cell lysate and identified a total of 3084 proteins in a typical experiment. The moderate separation performance of the mixed-bed IEX column facilitated the in-depth identification of the proteins in the complex sample. There were some acceptable inter-fraction overlaps. Nearly half (45.8%) of the proteins were only identified in single fractions, while 82.3% were identified in no more than 3 fractions. The identified proteins covered a broad range of pI, size and grand average hydrophobicity (GRAVY) values. Detailed analysis of proteins identified in each fraction elucidated the separation characteristics of mixed-bed IEX. Retention on mixed-bed IEX was associated, but not restricted to the extreme pI values (pI<5, pI>10) and to the percentage of charged residues of both signs. In conclusion, we have exploited the mixed-bed IEX column to establish an efficient and comprehensive identification method for complex samples.

Simultaneous Speciation of Iron(II) and Iron(III) by Ion Chromatography with Chemiluminescence Detection

This study reports on a method for the speciation of iron in aqueous samples by the simultaneous analysis of divalent and trivalent iron ions with ion chromatography equipped with chemiluminescence detection (IC-CLD). Ferrous and ferric ions are first chelated by pyridine-2,6-dicarboxylic acid (PDCA) to form complexed anions, and separated by a mixed-bed ion-exchange column. The separated complexed ions are then detected with a CLD system containing luminol and hydrogen peroxide in a basic solution. This luminescence system has a linear dynamic range of ca. 3 orders of magnitude, with method detection limits as low as 7 µg L(-1) for Fe(II) and 3 µg L(-1) for Fe(III), measured in the simultaneous detection mode. This system resists interferences from common cations such as Cd, Ca, Cr, Cu, Mg, Ni, Pb, and Zn. Evaluation by analyzing real samples shows that this method is rapid, accurate, sensitive, and selective.

Experience with Dilute Chemical Decontamination in Indian Pressurized Heavy Water Reactors

Abstract Dilute Chemical Decontamination (DCD) process has been used in several full system and components of nuclear coolant systems to effectively remove the radioactive contaminants that causes radiation field and consequent MANREM problem. The DCD process uses chemicals in very low concentrations (millimolar) and dissolves the oxide film along with the activity incorporated in the oxide film. In DCD process operated under the regenerative mode, the chemical formulation spent in the process of oxide dissolution is replenished by passing through cation exchange columns. Finally, after achieving sufficient decontamination of the system/component, the added decontamination chemicals along with the activities and metal ions released during the process are removed by mixed bed ion exchange columns and the system is restored to normal operating condition in a few days time. In PHWRs, the regenerative DCD process is applied for full primary coolant system decontamination. The chemicals are added directly to the heavy water coolant with the fuel in the core. In Indian PHWRs (MAPS#1&2, RAPS#1&2, NAPS#1&2 and KAPS#1), the process has been applied eleven times. A chemical formulation based on NTA, Citric acid and Ascorbic acid has been applied seven times with good results. Decontamination factors in the range 2-30 have been obtained in different components with good MANREM savings in the subsequent maintenance works. Efforts are on to modify the process to take care of the challenges posed by antimony isotopes. An inhibitor (Rodine-92B) based process was successfully tested in NAPS#2 for removing antimony isotopes (122Sb and 124Sb). Further refining of the antimony removal process is being worked out. Similarly, the process is being modified to effectively remove the hotspot causing stellite particles in the moderator system of PHWRs. A permanganate based process has been developed and tested in several adjustor rod drive mechanisms in KAPS and NAPS. The experience of applying/testing the DCD process in the Indian nuclear reactors is described in this paper.

Determination of trace transition metals in environmental matrices by chelation ion chromatography

Trace transition metals (Fe(3+), Mn, Cu, Cd, Co, Zn, Ni) in environmental samples were analyzed by chelation ion chromatography using a mixed bed ion-exchange column with pyridine-2,6-dicarboxylic acid (PDCA) and oxalic acid as eluent and large volume direct injection (1,000 μl). The two eluents, PDCA and oxalic acid, were tested, and repeatability and detection limits were compared. The total analysis time was ~15 min. The separation with PDCA was more successful than that obtained with acid oxalic. It was observed that utilizing PDCA resulted in lower detection limits, higher repeatability, and a quantitative detection of Cd and Mn, which coelute as a single peak when using the oxalic acid. At last, the PDCA calibration graphs resulted linear (r (2) > 0.999) in the range 0.4-1,000 μg/L. The procedure was applied to the analysis of metals in soils and in water samples. The results obtained from the analysis of natural waters have demonstrated that the method is simple and efficient, therefore, can be used for the determination of metals in natural waters using a continuous and automatic monitoring system.

Recovering antibody secretion using a hapten ligand as a chemical chaperone.

Engineered antibodies have come to the forefront as research reagents and clinical therapeutics. However, reduced stability or expression levels pose a major problem with many engineered antibodies. As a model for understanding functional consequences of variable region mutation, we have studied the assembly and trafficking of anti-phenylphosphocholine antibodies. Previously, we identified severe secretion defects because of mutations in the heavy chain second complementarity determining region, which is involved in antigen binding. Here we demonstrate that immunoglobulin secretion is increased up to 27-fold by incubating stably transfected PCG1-1 cells with cognate hapten p-nitrophenylphosphocholine. Secretion was unaffected by nonbinding analogs. Radiotracer and metabolic labeling experiments demonstrated specific cellular uptake of p-nitrophenylphosphocholine and increased intracellular heavy and light chain assembly. Brefeldin A inhibited hapten-mediated immunoglobulin secretion but not assembly, indicating that assembly occurs early within the biosynthetic pathway. Recovery of secretion correlated with antigen binding capacity, suggesting that the rescue mechanism involves stabilization of heavy and light chain variable domains. This model system provides the first demonstration that cognate ligands can increase intracellular assembly of functional anti-hapten antibody within mammalian cells and suggests that small molecules of appropriate specificity and affinity acting as chemical chaperones may find application for increasing or regulating immunoglobulin expression.

Optimization of the Simultaneous Determination of Cr(III) and Cr(VI) by Ion Chromatography with Chemiluminescence Detection

An optimized method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solutions using ion chromatography with chemiluminescence detection is described. Excellent resolution of the two chromium species was obtained using a single mixed-bed ion-exchange column with continuous elution. After postcolumn reduction of Cr(VI) to Cr(III), the light emitted during the Cr(III)-catalyzed oxidation of luminol with hydrogen peroxide was measured. Parameters affecting the postcolumn reactions such as reductant concentration, reductant mixing, point of luminol introduction, and luminol flow rate were optimized. The calibration curves in the range tested (0.01-50 μg L(-)(1)) were linear, and detection limits of 0.002 μg L(-)(1) for both Cr(III) and Cr(VI) were obtained. The results of the analyses of the water reference materials LGC CRM6010 and NIST SRM1643d with certified chromium values of 49 ± 4 and 18.53 ± 0.20 μg L(-)(1) and found to contain only Cr(III) were 49.2 ± 1.8 and 19.0 ± 1.5 μg L(-)(1), respectively. Values of 10.6 ± 0.5 and 10.1 ± 0.5 μg L(-)(1) were obtained when a simulated water sample containing 10 μg L(-)(1) Cr(III) and Cr(VI) was analyzed.

Simultaneous detection of monovalent anions and cations using all solid-state contact PVC membrane anion and cation-selective electrodes as detectors in single column ion chromatography

The overall efficiency of ion chromatographic procedures allows the possibility of routine separation and detection of common inorganic and organic anions and cations at low levels in a simultaneous system. A simple and rapid independent separation, and sensitive simultaneous detection of monovalent common anions and cations were achieved using 2 mM copper sulfate, (at pH: 5.40), as eluent with low cell-volume potentiometric detectors. This was established using all-solid state contact, tubular, PVC-matrix membrane anion and cation-selective electrodes in series as detectors with mixed-bed ion-exchange column in ion chromatography. The developed method is reproducible and highly selective to monovalent anions and cations, and takes less than 8 min. Under all operation conditions, the detection limits of the developed method, for potassium, rubidium, cesium, thallium(I), nitrite, nitrate, benzoate and bromide, were of the order of tens of ppb, for sodium, ammonium, chloroacetate, cyanate and chloride ions, values were of the order of hundreds of ppb for an injected volume of 20 μl. The method was flexible since most of anions do not interfere the detection of cations and most of cations do not affect the detection of anions, so that the method can be applied to many sample types e.g. environmental. The application of the method for river, sea and tap water samples were illustrated.

A general approach to desalting oligosaccharides released from glycoproteins.

Desalting of sugar samples is essential for the success of many techniques of carbohydrate analysis such as mass spectrometry, capillary electrophoresis, anion exchange chromatography, enzyme degradation and chemical derivatization. All desalting methods which are currently used have limitations: for example, mixed-bed ion-exchange columns risk the loss of charged sugars, precipitation of salt by a non-aqueous solvent can result in co-precipitation of oligosaccharides, and gel chromatography uses highly crosslinked packings in which separation of small oligosaccharides is difficult to achieve. We demonstrate that graphitized carbon as a solid phase extraction cartridge can be used for the purification of oligosaccharides (or their derivatives) from solutions containing one or more of the following contaminants: salts (including salts of hydroxide, acetate, phosphate), monosaccharides, detergents (sodium dodecyl sulfate and Triton X-100), protein (including enzymes) and reagents for the release of oligosaccharides from glycoconjugates (such as hydrazine and sodium borohydride). There is complete recovery of the oligosaccharides from the adsorbent which can also be used to fractionate acidic and neutral glycans. Specific applications such as clean-up of N-linked oligosaccharides after removal by PNGase F and hydrazine, desalting of O-linked glycans after removal by alkali, on-line desalting of HPAEC-separated oligosaccharides and beta-eliminated alditols prior to electrospray mass spectrometry, and purification of oligosaccharides from urine are described.

Application of chelation ion chromatography to the determination of lanthanides in agriculture

Lanthanides are widely present in soil and plant. In this paper, it is the first time that chelation ion chromatography is applied to analyse lanthanides in a series of samples in agriculture. This technique can eliminate bulk quantity of alkali, alkaline earth metals on chelating concentrator column (MetPac CC-1) and eliminate transition metals on cation exchange column (TMC-1) from complex matrices with ammonium acetate buffer while lanthanides are concentrated. It is shown to be capable of separating and determining all lanthanides on mixed-bed ion exchange column (CS5) in a wide variety of sample types with high accuracy. Elution is carried out with a concentration gradient of oxalic acid (Ox) and diglycolic acid (DGA), coupled with post-column spectrophotometric detection with 4-(2-pyridylazo)resorcinol (PAR) at 520 nm. It can determined ng ml −1 scales of lanthanides. The whole run time after sample injection is about 55 min.

On-Line Sample Pretreatment and Determination of Lanthanides in Complex Matrices by Chelation Ion Chromatography

The rapid determination of lanthanides in complex matrices has been developed by an on-line sample pretreatment of chelation ion chromatography. In the present system, selective chelating resin and sulfonated cation exchanger concentrated lanthanides while eliminating bulk quantities of alkali, alkaline earth and transition metals from sample matrices. The concentrated lanthanides which were separated on a mixed-bed ion exchange column were eluted by a concentration gradient of oxalic acid (Ox) and diglycolic acid (DGA), coupled with post-column spectrophotometric detection with 4-(2-pyridylazo) resorcinol (PAR) at 520 nm. The overall analysis time after sample digestion was less than 55 min. The method detection limits (signal-to-noise ratio 3:1) from heavy lanthanides to light lanthanides were in the range of 0.6–5.5 ng mL−1 and the R.S. Ds were within 1.8–5.5%. This method was applied to soil, ore, nodular cast iron, plant, grain, and rare-earth fertilizer samples. The results of those real sample analyses were satisfactory.

Behaviour of selenium and tellurium species and their determination by ion chromatography

An ion chromatographic method has been developed for the separation of Te (IV) and Se(IV) in hydrochloric acid mobile phases; the method has been used to determine tellurium in a high-purity non-stoichiometric semiconducting ZnCdTe-based material. Different cation-exchange columns (IonPac CS2, CS3, CS10), a mixed bed ion-exchange column (IonPac CS5), a multi-mode cation-exchange column (OmniPac PCX-500), anion-exchange columns (IonPac AS4, AS4A, AS5, AS5A, AS10, AS11) and a multi-mode anion-exchange column (OmniPac PAX-500) were evaluated for ion chromatographic separation of Se and Te and to study the chemical forms in which the analytes were eluted. The chromatographic data obtained enabled the calculation of both the sign and the chaarge of the eluting species.

Use of ion chromatography for the determination of transition metals in the control of sewage-treatment-plant and related waters

Transition metals [Fe(III), Fe(II), Cu, Ni, Zn, Co, Cd, Mn] were separated using a mixed-bed ion-exchange column (Dionex IonPac CS5A). A pyridine2–6-dicar☐ylic acid eluent was used and detection was accomplished using post-column reaction with 4-(2-pyridylazo)resorcinol and absorbance monitoring at 530 nm. Under the suggested chromatographic conditions both Mg 2+ and Ca 2+, up to 0.1 g/l and 0.3 g/l, respectively, do not interfere with separation quantitation. Detection limits from 0.06 μg/l for Co(II) to 0.38 μg/l for Fe(II). The calibration graphs were linear ( r 20.986) over two orders of magnitude (5–5000 μg/l). The selective separation of eight metals in 20 min was obtained and the method was applied to the analysis of natural and waste waters related to the maintenance of a sewage treatment plant.