Single-column Ion Chromatography Research Articles

Conductivity monitoring of inorganic anions with a Cu(II)-containing poly(3-methylthiophene) electrode in single-column ion chromatography

An amperometric detector unit equipped with a Cu(II)-containing poly(3-methylthiophene) working electrode is described for the single-column ion chromatographic detection of electroinactive inorganic anions, such as F −, Cl −, Br −, NO 2 − and NO 3 −. Chromatograms obtained with this unit and with a commercial conductivity detector are almost identical with regard to peak height. Thus, an amperometric unit employing this modified electrode can be used as a conductance monitor in ion chromatographic analysis. Although the responses of this electrode seem to be conductivity related, the detection principle is probably based on a dual mechanism involving equilibria between copper ions and various anions of the system in addition to simple conductivity changes associated with the passage of analyte plugs. This explains the difference in responses observed with platinum and stainless-steel electrodes used in the same cell configuration. The detector displays a linear range of at least two orders of magnitude on a logarithmic scale.

Single-column ion-chromatographic determination of chromium(VI) in aqueous soil and sludge extracts

Single-column ion-chromatography (SCIC) was investigated as a routine, rapid, precise and selective analytical method for the determination of chromium(VI) in aqueous extracts of soil and sewage sludge. Chromatographic parameters were optimized for determination of Cr(VI), NO − 3 and SO 2− 4. A low-capacity resin-based column was used for the separation and the anions were determined by conductometric detection. p-Hydroxybenzoic acid (5m M) at pH 8.5 was used as the eluent. The limit of detection, defined as S/ N = 3, was 92 μg/l. The resolution between Cr(VI) and SO 2− 4 was 2.8, the precision ranged from 0.9% for NO − 3 to 2.0% for Cr(VI) with a 500-μl injection. The SCIC results for Cr(VI) agreed closely with those obtained by inductively coupled argon-plasma emission and spectrophotometry.

Determination of borate in extracts of gypsiferous soils by single column ion chromatography

Abstract A high performance liquid chromatography apparatus with a resin based anion exchange column and a conductivity detector were used to develop a method for borate separation and quantification in extracts of gypsiferous soils. An eluant containing 5 mMNaOH and 0.5 mMNa‐benzoate was found to produce satisfactory chromato‐grams. Calibration curves were linear in the range l to 7 mg B/L. The recovery of ? in spiked samples had a mean and coefficient of variation of 99.6 and 2.2 percent, respectively. The presence of divalent cations caused baseline instability that was remedied by exchange with H+using Dowex 50–8X. The presence of sulfate extended analysis time and was removed by precipitation with BaCl2. Coloration by organic matter does not interfere with ? determination by this method, but individual simple organic acids may mask the borate peak

Single-column ion chromatography of passive monitors for atmospheric pollution

Nitrite, nitrate and sulfate anions deposited on passive monitors were determined by using single-column ion chromatography. These monitors were exposed outdoors for various periods of time in an atmosphere with a very low degree of pollution, and they were used to evaluate the rate of deposition of some corrosive species on metallic materials. Two types of passive monitors were studied, namely sulfation and nitration plates. Comparison of the results obtained by using the classical turbidimetric method and single-column ion chromatography shows that turbidimetry is inappropriate for low sulfate concentrations (<2.5 mg/plate) deposited on sulfation plates. Thus, ion chromatography should be used to obtain a representative value of sulfate deposition because it allows the determination of sulfate in amounts as low as 200 μg/plate without further preconcentration. For nitration plates, ion chromatography permits simultaneous determination of nitrite, nitrate and sulfate from the same plate, whereas only nitrite can be determined by the classical colorimetric method. Both gluconate/borate and phthalate eluents were investigated and the results show that phthalate eluent is more appropriate for these plates. It was found that the pH of the sample has an important effect on the area of the sulfate peak. For both eluents, the area increases when the sample pH is lower than 6. This demonstrates the importance of an adequate sample treatment before injection in order to obtain reproducible and accurate values.

Determination of tungstate in soils and sludges by using single-column ion chromatography

A procedure has been developed for the determination of tungstate at trace levels in aqueous extracts of soil and sludge by single-column ion chromatography (SCIC). Chromatographic parameters based on ion selectivity, time of determination and signal response were optimized for tungstate with the simultaneous detection of nitrate and sulfate. Chloride, phosphate, chromate, molybdate and vanadate were found not to interfere in the determination. A low-capacity resin-based column was used for the separation with p-hydroxybenzoic acid (5 mM) at pH 8.5 as the eluent. The limit of detection defined as three times the signal-to-noise ratio was 170 μg l −1 (2-ml sample). The resolution between tungstate and sulfate was R s=2.84. The results for aqueous extracts agree closely with those obtained by an accepted spectrophotometric method.

Performance of sulfation and nitration plates used to monitor atmospheric pollutant deposition in a real environment

Sulfation and nitration plates were exposed outdoors for various periods of time to evaluate their performance in a real environment. These passive monitors are used to estimate the deposition of pollutants on metallic surfaces, and thus to evaluate the influence of the atmosphere on the corrosion. Single-column ion chromatography was used to determine the quantity of anions absorbed on the plates. This technique is better than other analytical procedures such as turbidimetry or colorimetry because passive monitors exposed in an atmosphere with a low degree of pollution can be analyzed without preconcentration. However, the pH of the sample to be injected on the Chromatographic column must be adjusted to between 6.0 and 12.0 in order to obtain reproducible sulfate values. For sulfation plates, the additivity of the deposition process is excellent for a period of exposure up to 3 months, with a reproducibility of about 2%. For nitration plates, the deposition process is not cumulative due to a physical change of the monitor during exposure. The correlation between the amounts of sulfate found on sulfation and nitration plates was also examined.

Determination of trace amounts of molybdate in soil by ion chromatography

Trace amounts of molybdate (MoO2–4) in soil were determined by single-column ion chromatography (SCIC). The method is based on the chromatographic separation of MoO2–4 from other inherent ions (Cl–, NO–3, PO3–4 and SO2–4) and was characterised in terms of time of analysis, detection limits and column efficiency. Separation of the anions was compared with the use of resin-based and polymethacrylate (PMA) gel analytical columns with 5 mMp-hydroxybenzoic acid (pH 8.25) as the mobile phase. The analytes were quantified by conductimetry with a detection limit of 45 µg l–1 of MoO2–4(signal to noise ratio = 3). The SCIC method for the determination of MoO2–4 with the PMA column gave good separation and the results were comparable to those obtained with inductively coupled plasma optical emission spectrometry.

Preparation and use of latex-coated resins for anion chromatography

A procedure is described for the preparation of low-capacity anion-exchange resins for use in single-column ion chromatography. The resins are prepared by hydrophobically coating an anion-exchanging latex onto unfunctionalized resins made by Rohm & Haas. The resin exchange capacities are varied by changing the concentration of the sodium chloride or latex in the coating solution. Various resin matrices can be coated and capacities from 5 to over 400 μ equiv./g are obtained. The mechanism of latex adsorption is discussed and several highly efficient anion separations are presented.

Low-capacity quaternary phosphonium resins for anion chromatography

Trimethylammonium, tributylammonium and tributylphosphonium anion-exchange resins were synthesized and used for single-column ion chromatography. The three resins were prepared using a 7–12-μm polystyrene-divinylbenzene resin and are all of a similar, low capacity. The selectivity of these resins for mono- and divalent anions was evaluated and unique anion separations are presented.

Single‐Column Ion Chromatography: IV. Determination of Arsenate in Soils

AbstractA method has been developed for the determination of arsenate (AsO3−4) in aqueous soil extracts by single‐column ion chromatography (SCIC) at trace levels. The eluent stream consisted of 6 mM p‐hydroxybenzoic acid (PHBA) at pH 7.0. Separation was carried out on a low‐capacity anion‐exchange resin column with the anion species being quantified by conductometric detection. Resolution between AsO3−4 and PO3−4 was Rs = 1.93. The method allows precise (RSD, relative standard deviation = 1.12 to 7.87%) trace amount measurement of AsO3−4 (detection limit, 0.092 mg L−1) in the presence of Cl, NO−3, PO3−4 and SO2−4. The AsO3−4 signal becomes masked limiting separation and detection when PO3−4 exceeds 30 mg L−1. Under the conditions described, arsenite (AsO3−3) was not detected. Analysis of aqueous soil extracts for AsO3−4 by SCIC agrees closely with those values obtained by atomic absorption spectrometry and inductively coupled plasma emission.

Simultaneous analysis of selenate and selenite by single-column ion chromatography

A rapid, selective and sensitive method has been developed for the simultaneous determination of selenate [Se(VI)] and selenite [Se(IV)] at trace levels by single-column ion chromatography. p-Hydroxybenzoic acid (4 mM) at pH 8.0 was used as the eluent. A low capacity resin-based anion-exchange column was employed for the separation with conductometric detection for quantification. The method requires minimal sample pretreatment. Resolution (Rs) between Se(VI)/Se(IV) was 6.76. Chloride, nitrate and sulfate did not interfere with selenium separation. The detection limits for Se(VI) and Se(IV) were 0.06 μg/ml and 0.110 μg/ml, respectively. The relative standard deviation using a 500-μl loop was 0.90 to 1.86% for Se(VI) and Se(IV), respectively. The method was applied to analyze seleniferous soil samples.

Dynamic quenching of europium(III) and terbium(III) luminescence: a potential detection method in ion chromatography

Indirect detection methods based on UV absorption and fluorescence measurements are well known in single-column ion chromatography’. The detector responds to the chromophoric or fluorophoric eluent ions; a negative signal is observed, as the eluting analyte displaces an equal amount of eluent at the detector. As a consequence, low detection limits are attainable only if the analytical separation is performed at low eluent concentrations. In our laboratory, we have developed an indirect detection method based on dynamic quenching of luminescence*+. Here displacement effects and therefore eluent concentrations play no role. A decrease in signal is observed for analytes able to reduce the luminescence quantum yield of a luminescing compound present in the detector cell. Previously we made use almost exclusively of the phosphorophore biacetyl, present as a solute in the eluent, and successful experiments have been reported2+. Unfortunately, the need to remove oxygen completely from the whole high-performance liquid chromatographic (HPLC) system makes the experimental set-up more complicated than for HPLC with W absorption or fluorescence detection. To reduce or even eliminate this problem we have followed two approaches. First we developed a detection technique based on an immobilized phosphorophore, covalently bound via an alkyl spacer on glass or silica gel bead@. As a second approach, reported here, we utilized rare earth metal ions as luminescent probes. Europium (III) and terbium (III) emit long-lived luminescence in fluid aqueous solutions that is hardly or not influenced by the presence of oxygen. Europium and other lanthanide ions have been applied as luminescence probes in studies on the structures of biological macromolecules7 and polymeric material@ and as NMR shift reagent@. Several non-radioisotopic immunoassays make use of Eu3 + chelates as luminescent markers lo.1 l. Because of their long luminescence lifetimes (1O-5-1O-3 s), the combination with time-resolved luminescence detection techniques results in very sensitive methods12. The use of Eu3 + and Tb3+ as detection luminophores in LC in a sensitized luminescence mode has been described by DiBella et ~1.‘~. The organic compounds are excited by UV radiation, energy transfer from the triplet state of the organic compound to an excited state of the lanthanide ion occurs and luminescence of the lanthanide is detected. Interesting results were ob-

Separation of oxyanions of sulphur by single-column ion-chromatography

After stabilization of sulphite by addition of a five-fold excess of formaldehyde, mixtures of sulphite, sulphate and thiosulphate are readily separated by HPLC. For use with Vydac columns (302IC or 300IC) a suitable eluent is 1–3m M phthalic acid (pH 5–6), and the eluted ions may be detected by means of the change in refractive index or the absorbance at 290 nm. With a flow-rate of 2 ml/min, anion elution times are about 2.7 (0.7) min for HOCH 2SO − 3, 7.5 (2.6) min for SO 2− 4 and 8.4 (5.2) min for S 2O 2− 3, the values in parentheses being those for the shorter 300IC column. Detection limits for sulphite and sulphate were around 1 mg/l., with relative standard deviations of 2–3% at higher levels. The sensitivity for S 2O 2− 3 was an order of magnitude lower. The proposed method has advantages over earlier procedures based on alkaline eluents.

Low-cost rapid separation and determination of ionic species by single-column ion chromatography

Inorganic anions can be determined in natural waters using high-performance ion-exchange chromatography. Single-column ion chromatography has been used to minimize the instrumentation, total time and cost requirements of such analyses. The analsis speed can be enhanced through the use of shorter columns without significant losses in efficiency. Anions has been analysed using an “Ion-Guard” cartridge (30 mm × 4.6 mm) which is normally employed as a guard column of sample preconcentrator. Utilization of such cartridges is recommended for high-speed analysis of anions in relatively uncomplicated aqueous samples.

Application of a Portable Ion Chromatograph for Field Site Measurements of the Ionic Composition of Fog Water and Atmospheric Aerosolsa

Abstract For the analysis of selected organic and inorganic ions in atmospheric aerosol samples, Single Column Ion Chromatography was used. Atmospheric aerosol constituents were sampled with five-stage impactors, diffusion denuder trains and fog samplers. The concentrations of the components Cl−, NO− NO− SO− and hydroxymethylsulfonate (HMSA) were determined by anion chromatography, Fluoride, formate, acetate, glycolate/lactate, propionate and butyrate were analyzed with ion exclusion chromatography, whereas monovalent cations Na+, NH− and K+ with cation chromatography, Resolution of HMSA-formate and HMSA-chloride pairs which were the most problematic cases were studied. Cross interferences and detection limits of all the ions of interest were determined. The methods were applied in a field sampling campaign in the Po Valley.

Separation and Detection of Sulfur-Containing Anions Using Single-Column Ion Chromatography

Separation and Detection of Sulfur-Containing Anions Using Single-Column Ion Chromatography

Single Column Ion Chromatography: III. Determination of Orthophosphate in Soils

AbstractA chromatographic procedure was developed to determine orthophosphate in aqueous soil extracts by single column ion chromatography (SCIC) with conductimetric detection. The eluent stream consisted of 1.5 mM phthalic acid adjusted to pH 2.7 with formic acid. The method allows precise (RSD = 1.1‐3.3%) measurements of trace amounts of orthophosphate (detection limit = 0.3 µg L−1) in the presence of high background levels of Cl‐ and NO‐3. Analysis of orthophosphate by SCIC closely agrees to those values obtained with an AutoAnalyzer based on the Mo blue chromophore reaction. Under the chromatographic conditions described, elution of orthophosphate occurred at 6 min while Cl‐ and NO‐3 had respective retention times of 11 and 20 min. Single column ion chromatography proves to be a rapid and routine method for determination of orthophosphate with greater sensitivity than the conventional colorimetric methods.

Die Ionen-Chromatographie in der routinemäßigen Wasser- und Umweltanalytik

The Single Column Ion Chromatography (SCIC) using conductivity detection without suppressor column is introduced. Separations are described with more than 1000-fold difference in the anion concentration as well as a combination of Schoninger's hydrolizing process and SCIC, and the determination of weakly dissociated anions.

Three‐Minute Analysis of Chloride, Nitrate, and Sulfate by Single Column Anion Chromatography

AbstractAccepted techniques of single column ion chromatography of inorganic anions were extended to separation of chloride, nitrate, and sulfate using 15 mM phthalic acid as an eluent, permitting reduction of column length to 30 mm and thereby reducing analysis time to three min. Using a 50 µL sample loop, detection limits were 0.05 mmolc L−1 and coefficient of variation values ranged from 0.8 to 1.7% using peak height measurements and 0.8 to 8.1% using peak area measurements. This configuration is appropriate for routine analysis of soil water extracts and ground water.

Origin of system peaks in single-column ion chromatography of inorganic anions using high pH borate—gluconate buffers and conductivity detection

Single-column ion chromatography of inorganic anions with borate—gluconate buffers and conductivity detection produces system peaks as the result of complexation of polyvalent cations such as calcium. The complexes show retention due to ion-exchange and/or reversed-phase mechanisms. The system peaks can be avoided by treating the sample with a cation exchanger which replaces the polyvalent cations with sodium ions.