Suppressed Ion Chromatography Research Articles

Urinary thiosulfate determined by suppressed ion chromatography with conductimetric detection

Thiosulfate is a naturally occurring product of sulfur metabolism. Assays of urinary thiosulfate have been based on the reaction with cyanide to form thiocyanate. However, matrix interferences and background variation in endogenous thiocyanate excretion place constraints on this method for determination of physiological amounts of thiosulfate in urine. We describe a column-switching ion chromatographic separation for urinary thiosulfate that allows for sensitive and accurate detection by ion conductimetry. In 20 adult volunteers, we found a lower urinary thiosulfate (8.50±7.39 μmol/24 h, mean±S.D.) than others have described, although the upward skew of the results (median, 6.90; range, 0.84-32 μmol/ 24 h) was similar. However, we have not observed any of the interfaces and the sensitivityof our technique (<0.2 μmol/24 h) allows for detection of thiosulfate in all control samples. This sort of methodological improvement will be essential for any study of physiological thiosulfate metabolism.

Control of errors in anion chromatography applied to environmental research

Chemically suppressed ion chromatography has developed into a precise and reliable method for quantifying common anionic species. Equipment has improved, columns have been developed to offer faster analysis and three generations of chemical suppressors have evolved to provide easier care and improved performance. A range of sample types which include rainwater, soil solutions and canopy leachates have been analysed. A build-up of sample impurities gradually affects the performance of the column resulting in loss of separation and increase in mobile phase back-pressure over time. Approximately 8000 samples per annum have been analysed for chloride, nitrate and sulphate over a period of 11 years. A quality system describing calibration characteristics, measures of accuracy, precision and a model for quality control are presented.

Anions in mineral waters—Facilitated transition to ion chromatographic monitoring

The usability of suppressed ion chromatography for the determination of anions in various mineral waters was shown. Because of the great variety in the composition of these samples, individualized method development is necessary. A generalized approach to method development that enables the rapid optimization of the experimental conditions with the smallest number of necessary experimental steps was examined.

Prediction of Retention for Halide Anions and Oxoanions in Suppressed Ion Chromatography Using Multiple Species Eluent

The retention behavior of inorganic halide and oxoanions is studied as a function of changing eluent composition. The model developed for separation of Cl - , Br - , ClO 3 - , BrO 3 - , SeO 3 2- , SeO 4 2- , and PO 4 3- ions with eluent containing HCO 3 - , CO 3 2- , and OH - anions is utilized for determination of selectivity coefficients for sample and eluent species. It can also take into account the protonation of the sample ions. The model effectively characterizes the behavior of the analytes under elution conditions of practical importance. The predicted and measured retentions are in rather good agreement. The capacity factors determined for these anions make possible a reliable planning for IC separation of them with carbonate eluent in relatively wide ranges of concentration and pH. The different retention behaviors of mono-, di-, and trivalent anions as a function of pH are also interpreted in this eluent system

Chromatographic Simulation of the Effect of a Polyvalent Counter Ion on Retention Behavior and Peak Intensity of Sulfate.

The effect of a mobile phase polyvalent counter ion on the retention behavior and peak intensity of sulfate in non- suppressed ion chromatography was quantitatively studied using a chromatogram simulation method. In this study, both indirect photometric detection (IPD) method and conductometric detection (CD) method were evaluated. With the IPD method, the retention of sulfate was observed to decrease in the presence of the polyvalent counter ion (Trien) without any change in peak intensity. With the CD method, however, peak intensity of sulfate decreased and, under some conditions, gave a negative peak in simulation as was also observed in actual experiments. The present work demonstrates the possibility of predicting the effect of a polyvalent counter ion on sulfate retention without resorting to physical experiments.

Analysis of fluoride, acetate and formate in Bayer liquors by ion chromatography

Fluoride, acetate and formate in Bayer liquors have been separated on an AS5A column by suppressed ion chromatography using a very weak sodium hydroxide eluent before a rapid change in the eluent composition was required to elute the remaining liquor components. Fluoride data for four liquor samples analysed by ion chromatography with conductivity detection correlated well with potentiometric data obtained by a fluoride ion-selective electrode. Acetate and formate were analysed by conductivity and spectrophotometric detection and reasonable agreement was achieved.

Gradient ion chromatography of environmentally relevant anions in scrubbers of waste incinerators

Improved separations of a wide range of anions of environmental importance in scrubbers of waste incinerators were achieved by applying a Na2B4O7/NaOH composition gradient of low electrical conductivity in combination with suppressed ion chromatography. Fluoride, Acetate, Formiate and 16 other ions including Iodide could be separated within the same run in less than 20 minutes. The selective detection of small amounts of several anions in presence of excessive amounts of Chloride and Sulfate is discussed. Furtheron various adsorbents were tested for the removal of Phenol as a potential trouble shooting source in 5 ion chromatography. Depending on the analytical task and circumstances several adsorbents reveiled promising properties.

Nutrient adsorption kinetics of ion exchange resin capsules: A study with soils of international origin

Abstract A method based on use of ion exchange resin capsules was evaluated for simultaneous extraction of plant available nutrients (N, P, K, Ca, Mg, and Na) to determine its utility as a general soil testing procedure for soils of world‐wide origin. Nutrient release kinetics of soils representing many soil orders were measured in saturated soil paste during 14 d incubation periods. Suppressed ion chromatography was suitable for simultaneous determination of five cations in extracts from the resin capsules. The fractional power equation described well the cumulative nutrient adsorption by the resin as a function of time for all nutrients. The constants a and b in this equation combine quantitative levels of nutrient availability as well as transport and release mechanisms in the soil. Ranges of a and b in soil are presented and their relationships to other soil properties are discussed. A simple method for calculating kinetic constants in the power function based on only two incubation times is proposed....

Analyte identification in ion chromatography Electromigration governed chronoamperometric profiles

If a DC voltage is applied between two electrodes defining the boundaries of a small volume containing a stationary acid electrolyte, the resulting chronoamperogram is characteristic of the anion of the acid and can be used for identification purposes. Factors that effect the results obtained and their reproducibilities have been identified and studied using two 2-electrode cell designs. One parameter that affects the day-to-day reproducibility of the results and is relevant to the use of the technique as an adjunct to suppressed ion chromatography is the impurity level of the eluent. High purity electrodialytically generated eluents constitute one solution. To see if impurity problems could also be circumvented by an alternate experimental arrangement, a cell was devised in which the trapped eluite was subjected to electromigration using a third electrode and a high electric field. While the influence of the impurities on the chronoamperometric profile generated by the analyte ion of interest could be eliminated under the conditions of the present experiments, it is suggested that this design may be significant utility for future experiments, including tandem ion chromatography-capillary electrophoresis.

Analysis of sodium isethionate in soap and lye process streams by suppressed ion chromatography

Suppressed ion chromatography has been used to determine sodium isethionate in various soap production process streams at concentrations of 0.1–1.0%. The method was validated by spiking placebo soap and lye process stream samples. Overall recoveries in soap were 98.5 ± 2.3% (n=24). Recoveries in lye were 98.4 ± 2.8% (n=24).

Preparation of Sample Solution for Determination of Nitrate and Nitrite in Various Foods by Colorimetry and Ion Chromatography

A method for preparation of sample solution for determination of nitrate and nitrite in vegetables, beef and their processed foods by colorimetry and suppressed ion chromatography (IC) with UV detection has been developed.Nitrate and nitrite were simultaneously extracted from foods with sodium borate solution at 80°, then the extracts were cooled and filtered through an ultrafilter (Molcut II). Nitrite was determined in the filtrate by colorimetry, and nitrate by IC. In the case of determination of nitrate in foods containing more than 3% sodium chloride, the salt was eliminated from the extracts by using an On Guard-Ag cartridge. The recoveries of nitrate were 90.0-102.0% from foods fortified at 5-1, 000μg/g, and those of nitrite were 84.2-101.0% from foods fortified at 5-50μg/g.

Applications of an alternative stationary phase for the separation of anions by chemically suppressed ion chromatography

A hydroxymethyl methacrylate-based anion exchanger with quaternary amine functional groups is shown to have a proper selectivity for the separation of common inorganic anions on chemically suppressed ion chromatography systems. Its performance is comparable to the agglomerated pellicular-based anion exchangers commonly used for this purpose. The applications of this new anion exchanger as an alternative stationary phase for chemically suppressed ion chromatography are featured with separations of some simple inorganic and organic anions using both isocratic and gradient elution techniques.

Quantitation and measurement of equivalent conductance of unidentified analytes by suppressed ion chromatography using conductivity detection

Suppressed ion chromatography with conductivity detection was used to quantify organic anions in solution. A procedure is described whereby the normality and the equivalent conductance of unidentified analyte ions can be determined with an accuracy of greater than 90% using two different regenerants but only a single eluent. The proposed method is based on the fact that the conductivity detector's response is directly proportional to the concentrations of both the analyte and its counterions, which in suppressed IC are supplied by the regenerant. While results for monoprotic acids were excellent, results for polyprotic acids were less satisfactory, perhaps due to incomplete dissociation of the analyte.

Simultaneous Determination of Arsenite, Arsenate, Selenite, and Selenate by Suppressed Ion Chromatography

AbstractStudies of chemical processes involving As and Se in soil solution require accurate determination of arsenite, arsenate, selenite, and selenate. Many of the currently used speciation techniques rely on indirect measurement of one or more species. Direct, simultaneous measurement of these As and Se ionic species was achieved using a commercially available suppressed ion chromatography system and a Na2CO3‐NaHCO3 eluant. Electrochemical and conductivity detectors were used in series with a dual‐channel integrator to quantify arsenite, arsenate, selenite, and selenate. Resolution of the As and Se ionic species from the other ions depended on the nature of the eluant. An eluant containing 2 mM Na2CO3 and 1.7 mM NaHCO3 provided a good compromise between analyte resolution and time of analysis. Concentrations of 1 mg L−1 each of arsenite, arsenate, selenite, and selenate were measured in the presence of 50 mg L−1 each of F, Cl, NO3‐N, SO4‐S, and PO4‐P. Detection limits ranged from 0.016 mg L−1 for selenite to 0.120 mg L−1 for arsenate. The detection limits for arsenate and selenite obtained using this suppressed ion chromatographic technique were lower than values reported in the literature using nonsuppressed ion chromatography. Precision of analysis decreased with decreasing analyte concentration. The ion chromatographic method was compared to spectroscopic methods using analyses of soil solution, receiving As and Se spikes, and analyses of adsorption equilibrium solutions. The results of this study show that suppressed ion chromatography is a reliable method for determination of the As and Se oxyanions in soil solution.

Determination of sulfate in deep subsurface waters by suppressed ion chromatography

Determination of sulfate in deep subsurface waters by suppressed ion chromatography

Peak-shape analysis and noise evaluation in suppressed ion chromatography for ultra-trace ion analysis

Numerical analysis was used to study the performance of a suppressed ion chromatographic system with on-line preconcentration for ultra-trace ion determination in ultra-pure power plant waters. Peakshape analysis by the Edgeworth—Cramér series fitting method was applied in order to cheek non-linear concentration-dependent effects, so as to evaluate the best experimental practice with regard to the linear calibration range. Noise evaluation by Edgeworth-cramér fitting residuals and Fourier analysis is discussed in order to establish the detection limits. Results of the checks made for strictly linear conditions and determination of the quantification limits for sodium, chloride and sulphate ions are reported.

Determination of Thiocyanate in Human Urine Samples by Suppressed Ion Chromatography

A sensitive and simple method has been developed for the determination of thiocyanate in human urine samples by suppressed ion chromatography with conductivity detector in which a carbonate solution mixed with trace amount of 1, 3, 5-benzenetricarboxylate (BTC) was used as an eluent. This eluent made thiocyanate elution earlier than a single eluent of carbonate, and also caused the peak of chromatogram for thiocyanate to be sharper When a 3mM carbonate -2μM BTC solution was used for a 50-μl aliquot of sample solution, the calibration graph obtained for thiocyanate plotted as peak height vs. concentration was linear up to 0.05mM, and the detection limit as S/N 3 was 0.2μM of thiocyanate. The proposed method was successfully applied to the determination of thiocyanate in various human urine samples.

A rapid and sensitive ion chromatographic technique for the determination of sulfate and sulfate reduction rates in freshwater lake sediments

Newly developed low capacity columns were used in suppressed ion chromatography for rapid and highly reproducible determination of SO42− in porewater samples from freshwater sediments without preconcentration of samples. With a 50 μl injection the detection limit for SO42− was ca. 50 pmol (= 1 μM) with a precision of 1–3% at the 10–200 μM level and <1% at concentrations above 200 μM. SO42− could be measured in 4–5 min with the routinely used eluent (3.0 mM NaHCO3/0.8 mM Na2CO3). When the strength of the eluent was increased to 3.0 mM NaHCO3/2.0 mM Na2CO3, sulfate analysis was possible in less than 3 min, provided that samples were nitrate-free. Under these conditions S2O32− could also be sensitively determined in about 6 min. Examples of application of the method are given for measurements of sulfate reduction rates in freshwater sediment samples from Lake Constance.

Optimization of the procedure for the determination of alkali and alkaline-earth elements in sea water by suppressed ion chromatography

An ion chromatographic procedure is described for the determination of alkali and alkaline-earth metal ions in sea water the molar ratios of which, referred to lithium, are: 2.5 · 10 4 for sodium, 5 · 10 2 for potassium and calcium, and 3.5 · 10 3 for magnesium. Lithium, potassium, magesium and calcium are simultaneously analyzed after a 50-fold dilution, sodium is determined separately after a 2000-fold dilution. For all these elements, a dynamic range of several orders of magnitude and a R.S.D. varying from 0.2–2.2%, though typically lower than 1%, were found.

Simultaneous determination of arsenite, arsenate, selenite and selenate in waters using suppressed ion chromatography with ultraviolet absorbance detection

Using Dionex AS4A anion-exchange column, with micromembrane supressor and UV detector at 195 nm, arsenite, arsenate, selenite and selenate can be determined simultaneously in water samples. The mole fraction of sodium carbonate in the eluent as well as eluent concentration affected the retention times especially for the divalent anions. An eluent of 2.5 m M Na 2CO 3 and 0.75 m M NaHCO 3 was found to be the most suitable for sample analysis. The responses for all ions tested was linear in 0–5 mg 1 −1 range. The system can tolerate up to 1600 mg 1 −1 of SO 2− 4, before affecting arsenate peaks. Selenate peak area was not affected due to SO 2− 4 concentration up to 2000 mg 1 −1. The detection limits using 100-μl loop were 0.1 mg 1 −1 for AsO − 2 and SeO 2− 3 and 0.25 mg 1 t-1 AsO 3− 4 and SeO 2− 4.