Single-column Ion Chromatography Research Articles

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.

Chromatographic behavior of anions on polyelectrolyte sorbents based on silicagel

Polyelectrolyte anion exchangers based on commercially available nonsulfonated silicagels Silasorb 600 and Kromasil with modification of the latter by quaternized poly(4-vinylpyridine) have been proposed. Sorbents based on Kromasil allow simultaneous determination of 10 anions (CH3COO−, HCOO−, BrO3−, Cl−, NO2−, NO3−, I−, SCN−, ClO4−, SO42−) for 20 min and show high efficiency (up to 30000 tp/m) for NO3− in a variant of single-column ion chromatography with indirect spectrophotometric detection upon elution by the solutions of potassium hydrogen phthalate.

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.

A novel covalently modified aminated silica-based anion exchanger for ion chromatography

A novel method for the synthesis of anion exchangers for ion chromatography that provides the covalent attachment and spatial movement of the ion-exchange layer away from the silica surface is proposed. The new approach includes the following steps: alkylation of aminated silica with 1,4-butanediol diglycidyl ether and then amination using polyethyleneimine. The obtained anion exchanger allows the simultaneous separation of 11 anions (C2H5COO−, CH3COO−, HCOO−, BrO3−, Cl−,NO2− Br−, NO3− I−, SCN−, ClO4−) in 18 minutes and demonstrates good efficiency (up to 62,000 TP/m for I-) in the single column ion chromatography mode with indirect UV-detection using potassium hydrogen phthalate as an eluent.

Simultaneous determination of alkali, alkaline earth and transition metal elements in uranium and thorium based nuclear fuel materials by single column ion chromatography

A single-column ion chromatography (SCIC) for the simultaneous determination of alkali, alkaline earth and transition metal elements in UO2, ThO2 powders and sintered (Th, U) O2 pellet is described in this paper. Metrosep cation 1-2 analytical column containing poly butadiene-maleic acid (PBDMA) coated silica has been applied to the ion chromatographic separation of 12 cations (copper, lithium, sodium, ammonium, nickel, potassium, zinc, cobalt, manganese, magnesium, calcium and strontium) using an isocratic elution with tartaric acid and oxalic acid as mobile phase with non-suppressed conductivity detection. Mobile phase composition was optimized to 1 mM tartaric acid and 0.75 mM oxalic acid for the baseline separation of 12 cations. The calibration plots were linear in the range of 0.05–40 mg L−1 with regression coefficients better than 0.998. The relative standard deviations (RSDs) of the retention time, peak area and peak height were less than 1, 2.8 and 3.0%, respectively. The recoveries of the spiked samples for the cations were 94–110%. The method developed was validated by comparison with certified standards of UO2 and ThO2 powders.

Chelating resin immobilized sawdust packed chromatographic column: Application to separation and preconcentration of lead ion

Naturally abundant rubber sawdust has been utilized as a stationary support, which after immobilization with a chelating polyelectrolyte (xylenol orange as counterion) gets converted into a suitable column packing material for isolation and enrichment of trace level target analyte, accurately detectable by the technique of differential pulse anodic stripping voltammetry. The sorbent is robust and re-usable in column-chromatography without showing any leaching and interference complications. Its unique lead ion selectivity from multielemental complex matrices (synthetic water sample, blood serum) at optimized column conditions (pH 2.5 and flow rate 0.5 mL min−1) mitigates the usual problems of intermetallic and readsorption effects. Effects of flow rate, pH, equilibration time, and other variables are reported. The system has advantageous feature to be used in a single-column ion chromatography with satisfactory performance. A modest attempt has been made to determine lead fractions in human blood serum samples on the bases of selective retention of ionic and labile fractions on complexing resin.

Ammonium content and buoyancy in midwater cephalopods

The majority of squid families (Teuthoidea: Cephalopoda) exchange sodium for ammonium, creating a low-density fluid that imparts lift for neutral buoyancy. However, previous methods for measuring ammonium did not distinguish between NH 4 + and various other amine compounds. The present study, using single column ion chromatography, reassessed the cation concentrations in several midwater cephalopod species. High NH 4 + levels were confirmed for histioteuthid, cranchiid, and chiroteuthid and related squids. A strong relationship is reported between ammonium content and body mass in Histioteuthis heteropsis, suggesting a gradual accumulation of ammonium coincident with an ontogenetic migration to greater depths. The bathypelagic squids Bathyteuthis abyssicola and Bathyteuthis berryi, on the other hand, contained very little ammonium but rather contained large quantities of an as yet unidentified cation. The ecological significance of this compound is not yet known. Morphology in Bathyteuthid squids suggests that the unknown cation is contained intracellularly and so, unlike sequestered ammonia, does not diminish the space available for muscle tissue. Accordingly, protein measurements in B. berryi mantle muscle are on par with shallower-living muscular squids, and in situ submersible observations reveal strong locomotory abilities relative to other deep-water squids.

Silica gel-immobilized di[N-chloranil piperazinium-bis-sulfosalicylate]: Preparation, characterization and performance for chromatographic separation of metals

A chelating resin loaded with 5-sulfosalicylic acid, was prepared by ion-exchange. The resin, di-[N-chloranil piperazinium-bis-sulfosalicylatel was obtained by ion-exchange with piperazine-chloranil copolymer as matrix. A useful chromatographic packing is prepared by immobilizing the resin on silica gel. Detailed characterisation of this adsorbent has been carried out and selective adsorption conditions optimised for some heavy metals under static and dynamic conditions. The relatively fast kinetics of the adsorbent with time to reach half maximum adsorption (t1/2=2 min) and the level of attainment of equilibrium in 2 min (>50%) reveal the suitability of the resin in colum operation, especially in single column ion-chromatography. The metal ion content of the eluent was determined spectrophotometrically.

Application of Nafion/ Cobalt Hexacyanoferrate Chemically Modified Electrodes for the Determination of Electroinactive Cations by Ion Chromatography

AbstractAn amperometric detector based on the chemical modification of Nafion and cobalt (II) hexacyanoferrate (II, III) thin film (Nafion/Co‐CN‐Fe) onto a glassy carbon (GC) electrode was firstly developed for the determination of electroinactive cations (Li+, Na+, K+, Rb+, Cs+ and NH4+) in single column ion chromatography. A set of well‐defined peaks of electroinactive cation was obtained. The relative standard deviations (RSDs) of chromatographic peak height (nA) for these cations were all below 3.8%. The cations were detected conveniently in the linear concentration range of 6.0 × 10−6‐5.0 × 10−3 mol/L and their correlation coefficients were all above 0.99. The detection limits of the cations were 9.2 × 10−6 mol/L for Li+, 3.4 × 10−6 mol/L for Na+, 6.3 × 10−7 mol/L for K+, 7.8 × 10−7 mol/L for Rb+, 6.2 × 10−7 mol/L for Cs+ and 6.2 × 10−6 mol/L for NH4+, at a signal‐noise ratio of 3. The method was quick, sensitive, simple and was successfully applied to the analysis of rainwater samples. The electrode was stable for a 2 week period of operation with no evidence of chemical or mechanical deterioration.

Ion exchange chromatographic determination of olpadronate, phosphate, phosphite, chloride and methanesulfonic acid.

A method based on single column ion chromatography with UV detection was developed for purity testing and assay of monosodium olpadronate. The analyte aqueous solution is precipitated with methanol to enhance the impurities/olpadronate molar ratio, thus improving purity determination at trace levels. The resulting solution is injected into a standard chromatographic system with UV detector in indirect mode with a Waters IC Pak HR column using diluted nitric acid as the mobile phase. The method was fully validated according to ICH guidelines for the determination of phosphite, phosphate, chloride and methanesulfonic acid in olpadronate being suitable for purity testing and assay.

Determination of free and total sulfate and phosphate in glycosaminoglycans by column-switching high-performance size-exclusion and ion chromatography and single-column ion chromatography.

Analytical procedures for the determination of free and total sulfate and phosphate in glycosaminoglycans by high-performance liquid chromatography were studied. A column-switching method coupling high-performance size-exclusion chromatography (HPSEC) and ion chromatography (IC) is proposed for the determination of free anions. Good run-to-run and day-to-day precision values (RSD) of < 4.7% were obtained for both anions. Total anion contents were determined after wet acid hydrolysis with nitric acid-hydrogen peroxide (5 + 1) by single-column IC and ICP-AES elemental analysis in order to validate the results. Recoveries ranging from 94.6 to 99.0% for sulfate and from 80.8 to 94.0% for phosphate were obtained. Both HPSEC-IC and single-column IC methods were applied to the analysis of a low molecular mass heparin, a non-fractionated heparin and a chondroitin 4-sulfate. From the free and total sulfate determinations, the content of linked sulfur was calculated and ranged from 5.1 to 12.2% m/m.

Ion chromatography detector based on solid-state ion-selective electrode array

A variety of neutral carrier type ionophores for monovalent cations were employed to prepare solid-state cation-selective electrodes (SSEs) for use as a detector in single-column ion chromatography (IC). The polyurethane-based pseudoreference electrode made it possible to assemble an array type SSE detector for IC. An SSE-based detector provides not only the overall chromatogram for the separated ion species (monensin methyl ester–nonactin-based membrane), but also the enhanced chromatogram for specified ions of interest (valinomycin as K + and nonactin for NH 4 +). This feature makes it possible to perform highly quantitative analysis with low detection limits even if the separation efficiency of the ion-exchange is not sufficient. Since SSE-based IC detectors are easily miniaturized and replaceable at low cost, they are an ideal component of a portable IC system.

Simultaneous determination of chloride, nitrate and sulphate in vegetable samples by single-column ion chromatography

A new ion chromatography method is described for the simultaneous determination of Cl −, NO 3 − and SO 4 2−, using a selected eluent 1.3-mM sodium gluconate/1.3-mM borax (pH 8.5). The extraction methods of Cl −, NO 3 −, SO 4 2− in vegetables are studied. The determination limits of Cl −, NO 3 −, SO 4 2− are 0.17 μg/ml, 0.63 μg/ml and 0.81 μg/ml. The linear ranges are 0∼60 μg/ml, 0∼90 μg/ml and 0∼90 μg/ml. The relative S.D. are <2.5%. The mean recoveries of Cl −, NO 3 −, SO 4 2− in vegetables range from 97.0 to 104%.

Amperometric detection studies of Nafion/indium hexacyanoferrate film for the determination of electroinactive cations in ion chromatography.

An amperometric detector based on the chemical modification of Nafion and indium (III) hexacyanoferrate (II, III) thin film (Nafion/In-CN-Fe) onto a glassy carbon (GC) electrode, was first successfully used for the determination of electroinactive cations (Li+, Na+, K+, Rb+, Cs+, NH4+) in single column ion chromatography (IC). A set of well-defined peaks of electroinactive cations was obtained. The detection limits of the cations are 8.9 x 10(-6) mol/L for Li+, 2.3 x 10(-6) mol/L for Na+, 5.2 x 10(-6) mol/L for K+, 4.8 x 10(-6) mol/L for Rb+, 4.0 x 10(-6) mol/L for Cs+ and 5.3 x 10(-6) mol/L for NH4+ at a single-to-noise ratio of 3. The proposed method was quick, sensitive and simple. The cations in rainwater and mineral water were successfully analyzed by this method.

Trace metal analysis: selective sample (copper II) enrichment on an AlgaSORB column

A new approach to sample enrichment for copper(II) determination at trace level is reported. The silica-immobilised cationic polyelectrolyte, [poly ( N-xylene- N, N′ dicyclohexyl ethylenediamine dibromide)], capable of electrostatic binding with the biofilm of a natural alga Spirogyras sp is used in column separation for enrichment of trace analyte for accurate detection by differential pulse anodic stripping voltammetry. Algae–silica preparation termed as AlgaSORB-sp involves the molecular-level polymer coating as ‘spacer’ between algae and silica gel. This enables the entire algal film to be accessible for metal uptake and prevents the trace analytes becoming entrapped into the inner-core of the macroporous silica gel. The unique Cu 2+ ion-selectivity from multi-elemental complex matrices circumvents the usual problems of overlapping peaks and intermetallic effects. Effects of flow rate, pH, equilibration time and other variables are reported. The system has attractive features for application in single-column ion-chromatography with high durability, simplicity and economy.

Degradation of short-chain alkyl- and alkanolamines by TiO 2- and Pt/TiO 2-assisted photocatalysis

The photooxidation of C 2H 5NH 2, (C 2H 5) 2NH, HOC 2H 4NH 2, (HOC 2H 4) 2NH and (HOC 2H 4) 3N using TiO 2 and Pt/TiO 2 as photocatalysts has been investigated. A laboratory set up was designed and a study on the influence of the concentration of the photocatalyst, the pH-value and the structure of the amine performed. The photocatalytic process was optimized with respect to the concentrations of the model substances during degradation. The decrease of the amine concentrations was found to be maximum at a pH of 10. The time-dependence of the formation of cationic breakdown products, such as NH 3/NH + 4 and short-chain alkyl- and alkanolamines was studied by analyses with single column ion chromatography. The experimental data show that the photodegradation follows a Langmuir–Hinshelwood kinetic. The mineralization of the model substances also was monitored by measurements of the decrease of the TOC and of the formation of NO − 2 and NO − 3. The different mineralization efficiencies for the model substances studied are discussed with regard to their structure and adsorption behaviour on the photocatalyst. A possible breakdown mechanism involving the electrophilic attack of the hydroxyl radical is given. The applicability of the TiO 2-assisted photocatalytic degradation of C 2H 5NH 2 and (C 2H 5) 2NH was tested at the pilot plant-scale with real solar radiation. The degradation rates and products obtained were similar to those found in the laboratory experiments.

Separation and preconcentration of copper and cadmium ions from multielemental solutions using Nostoc muscorum-based biosorbents

Nostoc-based biosorbents (AlgaSORBs) useful as chromatographic column-packing materials were prepared by immobilizing cyanobacteria onto solid support in three different fashions: (i) cyanobacterial biofilm (Nostoc-dimethylformamide slurry) over polymer-modified silica gel, (ii) cyanobacterial biofilm over bare silica gel, and (iii) cyanobacteria as such onto polymer-modified silica gel. The materials were characterized for their stabilities and metal sorption/elution conditions under static and dynamic equilibrations. Preconcentrated metals from a test sample were detected following `standard addition' method using a differential pulse anodic stripping voltammetric technique. All sorbents showed 100% affinity for Cd2+ ion in a multielemental sample at pH 6.9 and a flow rate of 0.5 ml/min with a preconcentration factor varying between 28- and 75-fold. The first type of AlgaSORB was also found to be selective for Cu2+ ion in multielemental analysis at pH 5.2 and a flow rate of 1.0 ml/min with a preconcentration factor of 75. The low capacity and favourable kinetics of these sorbents for Cu2+, Cd2+, Zn2+ and Pb2+ ions reflect the suitability of AlgaSORB columns for satisfactory performance in single column ion-chromatography. The polymer spacer between cyanobacterial biofilm and silica gel plays a vital role in holding the immobilized biofilm resulting in better endurance and recyclability for the first type of biosorbent.

Degradation of nitrogen containing organic compounds by combined photocatalysis and ozonation

The combination of TiO 2-assisted photocatalysis and ozonation in the degradation of nitrogen-containing substrates such as alkylamines, alkanolamines, heterocyclic and aromatic N-compounds has been investigated. A laboratory set-up was designed and the influence of the structure of the N-compound, the TiO 2 and ozone concentration on the formation of breakdown products were examined. The experimental results showed that a considerable increase in the degradation efficiency of the N-compounds is obtained by a combination of photocatalysis and ozonation as compared to either ozonation or photocatalysis only. The mineralization of the model substances was monitored by measurements of the TOC and ion-chromatographic determinations of the formed NO 2 − and NO 3 − The temporal changes of concentrations of breakdown products, such as NH 4 +, short chain alkyl- and alkanolamines were determined by single column ion chromatography (SCIC) and as well as by electrospray mass spectrometry (EI-MS).

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.

Analysis of cations in drainage water and soil solution by single-column ion chromatography

Single-column ion chromatography (SCIC) for cation determination in drainage water and soil solution was tested. Using a 100-μl sample loop, the SCIC detection limits were 0.04 mg l −1 for Na +, 0.02 mg l −1 for NH 4-N, 0.06 mg l −1 for K +, 0.05 mg l −1 for Mg 2+, and 0.085 mg l −1 for Ca 2+. Results were highly reproducible in wide ranges of concentrations. Results obtained by the SCIC method were compared with those by atomic emission spectrometry (Na + and K +) and atomic absorption spectrometry (Mg 2+ and Ca 2+). Student's t-test and regression analysis showed that corresponding methods agree closely.