Toshio Takayanagi

Synthesis of novel chitosan resin possessing histidine moiety and its application to the determination of trace silver by ICP-AES coupled with triplet automated-pretreatment system.

A novel chitosan resin, cross-linked chitosan functionalized with histidine moiety (histidine-type chitosan resin), was synthesized for the collection and concentration of trace silver in aquatic samples. A triplet automated-pretreatment system (Triplet Auto-Pret System) installed mini-columns packed with the synthesized histidine-type chitosan resin was coupled with an inductively coupled plasma-atomic emission spectrometry (ICP-AES) for a rapid and sensitive analysis. Adsorption behavior of 50 elements on the histidine-type chitosan resin was examined. A trace amount of Ag(I) was shown a good adsorption in wide pH regions (pH 5-9), and Ag(I) adsorbed was readily recovered with 1 M nitric acid solution. The limit of detection (3sigma) for silver was 0.03 microg L(-1). The system was successfully applied to river water and dipped water in silver coated container.

Sequential-injection on-line preconcentration using chitosan resin functionalized with 2-amino-5-hydroxy benzoic acid for the determination of trace elements in environmental water samples by inductively coupled plasma-atomic emission spectrometry

A new chelating resin using chitosan as a base material was synthesized. Functional moiety of 2-amino-5-hydroxy benzoic acid (AHBA) was chemically bonded to the amino group of cross-linked chitosan (CCTS) through the arm of chloromethyloxirane (CCTS-AHBA resin). Several elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and rare earth elements (REEs), could be adsorbed on the resin. To use the resin for on-line pretreatment, the resin was packed in a mini-column and installed into a sequential-injection/automated pretreatment system (Auto-Pret System) coupled with inductively coupled plasma-atomic emission spectrometry (ICP-AES). The sequential-injection/automated pretreatment system was a laboratory-assembled, and the program was written using Visual Basic software. This system can provide easy operation procedures, less reagent consumption, as well as less waste production. Experimental variables considered as effective factors in the improvement sensitivity, such as an eluent concentration, a sample and an eluent flow rate, pH of samples, and air-sandwiched eluent were carefully optimized. The proposed system provides excellent on-line collection efficiency, as well as high concentration factors of analytes in water samples, which results in highly sensitive detection of ultra-trace and trace analysis. Under the optimal conditions, the detection limits of 24 elements examined are in the range from ppt to sub-ppb levels. The proposed method was validated by using the standard reference material of a river water, SLRS-4, and the applicability was further demonstrated to the on-line collection/concentration of trace elements, such as Ag, Be, Cd, Co, Cu, Ni, Pb, U, V, and REEs in water samples.

Adsorption behavior of uranium(VI) and other ionic species on cross-linked chitosan resins modified with chelating moieties.

Cross-linked chitosan resins with catechol (catechol-type chitosan, type 1 and type 2), iminodiacetic acid (IDA-type chitosan), iminodimetylphosphonic acid (IDP-type chitosan), phenylarsonic acid (phenylarsonic acid-type chitosan), or serine (serine-type chitosan) were prepared for the collection and concentration of uranium(VI). The adsorption behavior of U(VI) and other ionic species, such as metal ions and oxo-acid ions, on the cross-linked chitosan (base material) and chitosan resins modified with chelating moieties was examined using a column procedure. Especially, the catechol-type chitosan (type 2) adsorbed U(VI) at pH 2-7, and selectively collected U(VI) at acidic pH regions by forming a stable chelate with hydroxyl groups of catechol moiety introduced to the chitosan. Also, the adsorption properties of cationic and anionic species present in aquatic media were elucidated. The adsorption ability for U(VI) was in the order: catechol-type chitosan (type 2)>serine-type chitosan>phenylarsonic acid-type chitosan>the others. The catechol-type chitosan (type 2) was useful for the collection and concentration of uranium(VI).

Electrophoretic Mobility Study of Ion Association Between Aromatic Anions and Quaternary Ammonium Ions in Aqueous Solution

The ion association reaction between aromatic anions and quaternary ammonium ions in aqueous solutions was investigated through mobility changes in capillary electrophoresis. The electrophoretic mobility of aromatic anions decreased with increasing amount of quaternary ammonium salt added to the migrating solutions. The change in mobility of anions due to the ion association was found and was treated with a least-squares method, giving ion association constants. The ion associability order of the isomers of aromatic anions was found to be naphthalene-2,6-dicarboxylate > naphthalene-2,3-dicarboxylate, naphthalene-2-sulfonate > naphthalene-1-sulfonate and terephthalate > isophthalate > phthalate. The order of the ion associability of naphthalene-1,5- and -2,6-disulfonate reversed depending on the alkyl chain length of the pairing cation. The order of ion associability of quaternary ammonium ions was found to be tetraamylammonium > tetrabutylammonium > tetrapropylammonium ≈ octyltrimethylammonium ≈ hexyltrimethylammonium > tetraethylammonium > tetramethylammonium, and suggested that ion association in aqueous solution was governed by the hydrophobicity of the pairing cation.

Separation and determination of haloperidol, parabens and some of their degradation products by micellar electrokinetic chromatography

A micellar solution containing phosphate buffer, anionic surfactant, and water-miscible organic solvent was employed as a migration solution for the separation and the quantification of eleven analytes by micellar electrokinetic chromatography (MEKC): the analytes examined were haloperidol, methylparaben, ethylparaben, n-propylparaben, iso-propylparaben, n-butylparaben, iso-butylparaben, sec-butylparaben, 4-(4-chlorophenyl)-4-hydroxypiperidine, 4-fluorobenzoic acid and 4-hydroxybenzoic acid. In order to provide good separation between micelle and haloperidol, which showed strongest interaction with the micelle among the analytes, surfactant concentrations and organic modifier percentages were studied with phosphate buffer at pH 7.0. All the analytes were successfully resolved when 10 mM sodium dodecylsulfate and 15% ethanol were contained in the migration solution; the time window was very wide in the range from 14.8 to 65.5 min. Optimized applied voltage at 30 kV and capillary temperature at 45 degrees C enable analyze all compounds in less than 17 min with the best resolution, the shorter migration time window, the highest precision and lowest detection limit.

Separation of Divalent Aromatic Anions by Capillary Zone Electrophoresis Using Multipoint Ion Association With Divalent Quaternary Ammonium Ions

Positional isomers of naphthalenedisulfonate (NDS), naphthalenedicarboxylate (NDC) and phthalate were separated using an ion association reaction in aqueous solution followed by capillary zone electrophoresis with a polymer coated capillary. By using divalent quaternary ammonium ions, four NDS isomers and three NDC isomers were completely resolved, although some of the isomers were not resolved with tetrabutylammonium ion. Ion association constants, Kass, between the anions and the divalent quaternary ammonium cations were also determined by analyzing the change in electrophoretic mobility using a non-linear least-squares method. The Kass values of the anions obtained with the divalent cations were larger than those with tetrabutylammonium ion because of an increased electrostatic interaction. The ion associability was also explained on the basis of a distance-fitting concept and the hydrophobicity concept of the pairing cations. Ion associability was also improved by using a better distance-fitting pairing ion. From the results obtained, it was suggested that the charge–charge distance in cationic and anionic molecules must be close, and the charge–charge distance of the divalent cations was about 0.2 nm longer than that of divalent anions for good ion associability (a distance-fitting concept).

Electrophoretic mobility study on ion-ion interactions in an aqueous solution

Ion-ion interactions between anions and their pairing ions in aqueous solutions were studied through the measurements of electrophoretic mobilities of analyte ions in capillary zone electrophoresis, where the electrophoretic method for the analysis of ion association reaction is shown to be more useful than the conductometric method widely used in the analysis of the reactions. The electrophoretic mobility of monovalent inorganic anions was almost identical even when the concentrations of alkali metal ions and quaternary ammonium ions in the migrating solution were varied up to 15 mM. On the other hand, the electrophoretic mobility of organic anions, such as monovalent and divalent anions, decreased with increasing concentrations of quaternary ammonium ions. Changes in the electrophoretic mobilities were analyzed by a non-linear least-squares method giving ion association constants. The results indicate that the proposed method is applicable to the analysis of such reactions to give the mobility change. The ion association constants obtained in an aqueous solution were related to the extraction constants of the ion associates, and the contributions of the association process and the distribution process were clarified.

Fabrication of C60 field-effect transistors with polyimide and Ba0.4Sr0.6Ti0.96O3 gate insulators

A flexible C60 field-effect transistor (FET) device has been fabricated with a polyimide gate insulator on the poly(ethylene terephthalate) substrate, and n-channel normally off FET properties are observed in this FET device. The field-effect mobility, μ, is estimated to be ∼10−2cm2V−1s−1 at 300K. Furthermore, the C60 FET has been fabricated with a high-dielectric Ba0.4Sr0.6Ti0.96O3 (BST) gate insulator, showing n-channel properties; the μ value is estimated to be ∼10−4cm2V−1s−1 at 300K. The FET device operates at very low gate voltage, VG, and low drain-source voltage, VDS. Thus these C60 FET devices possess flexibility and low-voltage operation characteristic of polyimide and BST gate insulators, respectively.

Equilibrium analysis of reactions between aromatic anions and nonionic surfactant micelles by capillary zone electrophoresis

Separability of some positional isomers of aromatic anions by capillary zone electrophoresis was improved by adding nonionic surfactants to a migrating solution. Eleven kinds of aromatic anions, including positional isomers, were used as analytes, and Brij-35, Brij-58 and Brij-78 were investigated as nonionic surfactants to form micelles, where hydrophobicities are different from each other. Increasing the concentration of the surfactants developed the separability of the anionic isomers. The interaction between the anions and the nonionic surfactant micelles is also investigated through the change in the electrophoretic mobility, and the binding constants are determined. Apparent electrophoretic mobility of the anions decreased with increasing concentrations of the nonionic surfactants. The decrease in the mobility, as well as the binding constant, was larger in the monovalent anions than in the divalent anions, which indicates that the interaction or reactivity of the monovalent analytes is higher than that of the divalent analytes. The reactivity of each anion was almost identical even when the kinds of the surfactants were changed, suggesting that the hydrophobicity of the polyoxyethylene group in the surfactant would have the main role for binding the analytes. The reactivity tendency among the positional isomers was almost similar to that in ion association-capillary zone electrophoresis using tertabutylammonium ion as a pairing ion. The results obtained in this work suggest that the anions are bound to the micelles by the hydrophobic interaction between analyte anions and the polyoxyethylene moiety of the surfactant micelles. Changes in the fluorescence intensity of the anions were also investigated; the results can explain well the mobility changes of the analytes.

Investigation of salicylaldehyde-5-sulfonate as a precolumn derivatizing agent for the determination of n-alkane diamines, lysine, diaminopimelic acid, and isoniazid by capillary zone electrophoresis

Reactions of primary amines with salicylaldehyde-5-sulfonate (SAS) lead to the formation of stable Schiff bases at weakly alkaline pH and at moderate temperature in an ethanol-rich aqueous solution. Some alkane diamines were converted to salicylaldimine with SAS, and the products were resolved and detected by capillary zone electrophoresis (CZE). The reactivity of SAS was applied also to the derivatization of amino acids. Optimal conditions for the analysis of lysine in the presence of diaminopimelic acid, the metabolite of lysine, were investigated. Addition of Na(2)SO(4) into the migrating solution enhanced the stacking effect, and led to increase in the detection limits. Another advantage of the use of SAS is its ability to form stable water-soluble metal chelate as Schiff base ligands. For practical analysis, the copper chelate of the Schiff base of isoniazid, which is known as the most active antibacterial used in the treatment of pulmonary tuberculoses, was investigated, and the detection limit of isoniazid was improved in the magnitude of 11 times compared with the one of free isoniazid.