Kazuhiko Tanaka

Simultaneous spectrophotometric determination of phosphate and silicate ions in river water by using ion-exclusion chromatographic separation and post-column derivatization

The simultaneous spectrophotometric determination of phosphate and silicate ions in river water was examined by using ion-exclusion chromatography and post-column derivatization. Phosphate and silicate ions were separated by the ion-exclusion column packed with a polymethacrylate-based weakly acidic cation-exchange resin in the H(+)-form (TSKgel Super IC-A/C) by using ultra pure water as an eluent. After the post-column derivatization with molybdate and ascorbic acid, so-called molybdenum-blue, both ions were determined simultaneously by spectrophotometry. The effects of sulfuric acid, sodium molybdate and ascorbic acid concentrations and reaction coil length, which have relation to form the reduced complexes of molybdate and ions, on the detector response for phosphate and silicate ions were investigated. Under the optimized conditions (color-forming reactant, 50 mM sulfuric acid-10 mM sodium molybdate; reducing agent, 50 mM ascorbic acid; reaction coil length, 6 m), the calibration curves of phosphate and silicate ions were linear in the range of 50-2000 microg L(-1) as P and 250-10,000 microg L(-1) as Si. This method was successfully applied to water quality monitoring of Kurose-river watershed and it suggested that the effluent from a biological sewage treatment plant was significant source of phosphate ion in Kurose-river water.

Ion-exclusion/cation-exchange chromatographic determination of common inorganic ions in human saliva by using an eluent containing zwitterionic surfactant.

Ion-exclusion/cation-exchange chromatography with an eluent containing the bile salt-type zwitterionic surfactant CHAPS was performed in order to evaluate variations in anion (SO(4)(2-), NO(3)(-), and SCN(-)) and cation (Na(+), K(+), NH(4)(+), Mg(2+), and Ca(2+)) concentrations in human saliva. CHAPS prevents the adsorption of proteins to the stationary phase, i.e., weakly acidic cation-exchange resin, since it aggregates proteins without denaturing them. Addition of 1mM CHAPS to the eluent comprising 6mM tartaric acid and 7 mM 18-crown-6 yielded reproducible separations of anions and cations in protein-containing saliva. The resolutions of anions and cations were not significantly affected by the addition of CHAPS to the eluent. The concentrations of Na(+) and K(+) varied before and after meals; or that of SCN(-), upon smoking. The relative standard deviations of peak areas ranged from 0.3 to 5.1% in 1 day (n=20) and from 1.4 to 5.8% over 6 days (n=6).

Ion-exclusion/adsorption chromatography of dimethylsulfoxide and its derivatives for the evaluation to quality-test of TiO2-photocatalyst in water

Ion-exclusion/adsorption chromatography of dimethylsulfoxide (DMSO) and its derivatives, i.e., methanesulfinic acid (MSI), methanesulfonic acid (MSA) and sulfuric acid (SA), was developed in order to clear the decomposition mechanism of DMSO on quality-test of TiO(2)-photocatalyst in water. The separation was achieved by the adsorption effect for DMSO and ion-exclusion effect for MSI, MSA and SA under optimum conditions, using a weakly acidic cation-exchange resin column with 20mM succinic acid as the eluent. In this system, DMSO and MSI with UV at 195nm and MSA and SA with conductivity detection were consecutively determined by single injection and single separation column. This method was used to monitor the artificial decomposition of DMSO induced by a photocatalyst. The concentration of DMSO by active oxygens (e.g., OH radical) generated from surface of photocatalyst was found to be decreased through the stoichiometric reaction in the order of MSI, MSA and SA.

Ion-exclusion chromatography with the direct UV detection of non-absorbing inorganic cations using an anion-exchange conversion column in the iodide-form.

An ion-exclusion chromatographic method for the direct UV detection of non-absorbing inorganic cations such as sodium (Na(+)), ammonium (NH(4)(+)) and hydrazine (N(2)H(5)(+)) ions was developed by connecting an anion-exchange column in the I(-)-form after the separation column. For example, NH(4)(+) is converted to a UV-absorbing molecule, NH(4)I, by the anion-exchange column in the I(-)-form after the ion-exclusion separation on anion-exchange column in the OH(-)-form with water eluent. As a result, the direct UV detection of Na(+), NH(4)(+) and N(2)H(5)(+) could be successfully obtained as well as the well-resolved separation. The calibration graphs of the analyte cations detected with UV at 230nm were linear in the range of 0.001-5.0mM. The detection limits at S/N=3 of the cations were below 0.1muM. This method was applied to real water analysis, the determination of NH(4)(+) in river and rain waters, or that of N(2)H(5)(+) in boiler water, with the satisfactory results. This could be applied also to low- or non-absorbing anions such as fluoride or hydrogencarbonate ions by the combination of a weakly acidic cation-exchange resin in the H(+)-form as the separation column and the anion-exchange conversion column.

Simultaneous analysis of silicon and boron dissolved in water by combination of electrodialytic salt removal and ion-exclusion chromatography with corona charged aerosol detection

Selective separation and sensitive detection of dissolved silicon and boron (DSi and DB) in aqueous solution was achieved by combining an electrodialytic ion isolation device (EID) as a salt remover, an ion-exclusion chromatography (IEC) column, and a corona charged aerosol detector (CCAD) in sequence. DSi and DB were separated by IEC on the H(+)-form of a cation exchange resin column using pure water eluent. DSi and DB were detected after IEC separation by the CCAD with much greater sensitivity than by conductimetric detection. The five-channel EID, which consisted of anion and cation acceptors, cathode and anode isolators, and a sample channel, removed salt from the sample prior to the IEC-CCAD. DSi and DB were scarcely attracted to the anion accepter in the EID and passed almost quantitatively through the sample channel. Thus, the coupled EID-IEC-CCAD device can isolate DSi and DB from artificial seawater and hot spring water by efficiently removing high concentrations of Cl(-) and SO4(2-) (e.g., 98% and 80% at 0.10molL(-1) each, respectively). The detection limits at a signal-to-noise ratio of 3 were 0.52μmolL(-1) for DSi and 7.1μmolL(-1) for DB. The relative standard deviations (RSD, n=5) of peak areas were 0.12% for DSi and 4.3% for DB.

Utilization of a diol-stationary phase column in ion chromatographic separation of inorganic anions

We describe the ion chromatographic separation of inorganic anions using a diol-stationary phase column (-CH(OH)CH(2)OH; diol-column) without charged functional groups. Anions were separated using acidic eluent as in typical anion-exchange chromatography. The retention volumes of anions on the diol-column increased with increasing H(+) concentration in the eluent. The anion-exchange capacities of diol-columns in the acidic eluent (pH 2.8) were larger than that of zwitterionic stationary phase column but smaller than that of an anion-exchange column. The separation of anions using the diol-column was strongly affected by the interaction of H(+) ions with the diol-functional groups and by the types of the eluents. In particular, the selection of the eluent was very important for controlling the retention time and resolution. Good separation was obtained using a diol-column (HILIC-10) with 5 mM phthalic acid as eluent. The limits of detection at a signal-to-noise ratio of 3 ranged from 1.2 to 2.7 μM with relative standard deviations (RSD, n=5) of 0.04-0.07% for the retention time and 0.4-2.0% for the peak areas. This method was successfully applied to the determination of H(2)PO(4)(-), Cl(-), and NO(3)(-) in a liquid fertilizer sample.

Use of potassium-form cation-exchange resin as a conductimetric enhancer in ion-exclusion chromatography of aliphatic carboxylic acids

In this study, a cation-exchange resin (CEX) of the K(+)-form, i.e., an enhancer resin, is used as a postcolumn conductimetric enhancer in the ion-exclusion chromatography of aliphatic carboxylic acids. The enhancer resin is filled in the switching valve of an ion chromatograph; this valve is usually used as a suppressor valve in ion-exchange chromatography. An aliphatic carboxylic acid (e.g., CH(3)COOH) separated by a weakly acidic CEX column of the H(+)-form converts into that of the K(+)-form (e.g., CH(3)COOK) by passing through the enhancer resin. In contrast, the background conductivity decreases because a strong acid (e.g., HNO(3)) with a higher conductimetric response in an eluent converts into a salt (e.g., KNO(3)) with a lower conductimetric response. Since the pH of the eluent containing the resin enhancer increases from 3.27 to 5.85, the enhancer accelerates the dissociations of analyte acids. Consequently, peak heights and peak areas of aliphatic carboxylic acids (e.g., acetic acid, propionic acid, butyric acid, and valeric acid) with the enhancer resin are 6.3-8.0 times higher and 7.2-9.2 times larger, respectively, than those without the enhancer resin. Calibrations of peak areas for injected analytes are linear in the concentration range of 0.01-1.0mM. The detection limits (signal-to-noise ratio=3) range from 0.10 microM to 0.39 microM in this system, as opposed to those in the range of 0.24-7.1 microM in the separation column alone. The developed system is successfully applied to the determination of aliphatic carboxylic acids in a chicken droppings sample.

Single injection ion-exclusion/cation-exchange chromatography for simultaneous determination of organic/inorganic anions, inorganic cations, and ethanol in beer samples

Multicomponent simultaneous analysis is important for management programs, which are required in beer industries because the beer constituents measure by combining several methods in the present. In response to a requirement, our research group developed single sample injection ion chromatography systems, which comprise ion-exclusion/cation-exchange chromatography (IEC/CEC) and post-column derivatization and show promise for simultaneously determining concentrations of organic and inorganic species and alcohol commonly found in beer. Optimal chromatographic resolutions for determining 17 different species in beer samples by IEC/CEC were obtained on a H+-formed weakly acidic cation-exchange resin column with an eluent comprising 2 mM phthalic acid and 1 mM 18-crown-6. Consequently, the usefulness of developed method for monitoring beer samples was demonstrated in terms of beneficial information such as dependency of K+ concentration on the malt amount, influences of organic anion concentrations on different types of bottling methods, and validation of ethanol concentrations displayed in the ingredient table.

Application of ion chromatography for the assessment of cadmium adsorption in simulated wastewater by activated carbon

A separation for Cd2+ and its interferences of common cations (Na+, NH+, K+, Mg2+, and Ca2+) was performed. Cation-exchange ion chromatography for Cd2+ and common cations separation on a weakly acidic H+ forming cation-exchange resin was investigated and applied to test the efficacy of activated carbon in the removal of Cd2+ from simulated wastewater. The difference of retention volumes between Ca2+ and Cd2+ was 0.45 mL for oxalic acid with a concentration of 1.75 mM, and the retention volume drastically decreased when the oxalic acid concentration increased in the eluent. Considering the prevailing conditions for TOSOH TSK gel Super IC A/C at 40°C with a least pH limit of 2.0, 1.75 mM of oxalic acid was selected for rapid analysis with pH of 2.3. Applying 50 μL sample injection, the calibration curve was linear for tested standard samples ranging from 0.05 to 2.0 mg/L, the detection limit (S/N = 3) was 0.066 mg/L (0.583 μM), and the analysis was applicable with coexisting Ca2+ up to 10.0 mg/L (250 μM) while other cations did not interfere. It was possible to analyze three samples within an hour. The application of this method on Cd2+ adsorption indicated the effectiveness of the method for heavy metals’ analysis.