BUNSEKI KAGAKU Abstracts

Vol. 52 No. 9

September, 2003

Research Papers

Discrimination of Japanese sake using a portable near-infrared spectrometer and chemometrics

Tomoaki Sato¹, Masanori Kumagai^1,2, Toshio Amano³ and Nobuaki Ogawa¹

(Received 24 March 2003, Accepted 19 May 2003)

Using a portable near-infrared (NIR) spectrometer and a principal-component analysis, we discriminated Japanese sake and added a chemical explanation for the discrimination. From a wavelength contribution spectra, which were obtained by a principal-component analysis of the NIR spectra data, we extracted and found high contribution of alcohol-CH₃, -CH₂-, R-OH for the first principal component (PC1), protein-NH₂, -CONH₂, -CONH-, -CH₃, -CH₂- for PC2, and starch-CH₃, -CH₂-, and starch-OH for PC3. The differences between the NIR spectra discriminated “Junmaishu” and the other in PC1, “Daiginjoushu” and the other in PC2, and three groups (“Junmai-daiginjoushu” and “Honjouzoushu”, “Futuushu” and “Daiginjoushu”, “Junmaishu”) in PC3, respectively. This shows that “Futuushu” and “Honjouzoushu” have approached in spectral means to “Daiginjoushu” and “Junmai-daiginjoushu”, which are generally appreciated in the market, by adding brewing-alcohol, saccharides, and acidulant etc. We can demonstrate that a portable and in situ measurable PlaScan-SH is very useful for the discrimination of Japanese sake. Furthermore, we suggested that by using the base of those kinds of data and chemical information obtained in this study, one could brew and produce an appreciated, modern and popular Japanese sake for the market.

Keywords : near-infrared spectroscopy; principal component analysis; portable spectrometer; discrimination; Japanese sake.

Surface-enhanced infrared absorption spectrometry of L-cysteine on laser-deposited gold nanoparticles

Hideyuki Hisanabe¹, Yasuro Niidome², Hironobu Takahashi¹ and Sunao Yamada²

(Received 28 April 2003, Accepted 3 June 2003)

Gold nanoparticles were successfully deposited onto a poly(tetrafluoroethylene) (PTFE) membrane filter by pulsed 532-nm laser irradiation in a 2-propanol solution containing HAuCl₄. The resulting membrane filters were used as substrates for infrared (IR) absorption spectrometry. A substantial enhancement in the IR spectrum of L-cysteine was observed by using this substrate. The degree of enhancement was roughly twice compared with the case of PTFE membrane filters without gold nanoparticles.

Keywords : gold nanoparticles; surface enhanced infrared absorption; SEIRA; cysteine; PTFE membrane filter.

Mechanistic study of the electron transfer of L-ascorbic acid at an oil/water interface by a digital simulation of cyclic voltammograms

Takayasu Sugihara¹, Hiroki Hotta¹ and Toshiyuki Osakai¹

(Received 2 May 2003, Accepted 4 June 2003)

L-ascorbic acid (AsA), a water-soluble antioxidant, is known to exhibit a synergistic inhibition of oxidation by reacting with a lipophilic antioxidant, such as vitamin E, at biomembrane surfaces. In this study, we electrochemically investigated the oxidation of AsA by chloranil (Q) at a nitrobenzene (NB)/water (W) interface, which is considered to be the simplest model of a biomembrane, by using a four-electrode electrolytic cell. The cyclic voltammograms obtained by changing the pH of the W phase and the concentrations of AsA and Q were analyzed using a digital simulation technique. Regression analyses based on various reaction mechanisms have supported the previously proposed mechanism in which the oxidation of AsA occurs not at the NB/W interface, but homogeneously in the W phase. However, it has been clarified that the two electron oxidation of AsA occurs in two one-electron steps.

Keywords : ascorbic acid; chloranil; oil/water interface; cyclic voltammetry; digital simulation; reaction mechanism.

Construction of an enzymatic sensor for visual measurements with redox dyes immobilized on the inner surface of a glass tube

Katsuyuki Maeno¹, Mitsuru Abo¹ and Akira Okubo¹

(Received 8 May 2003, Accepted 10 June 2003)

An enzymatic glucose sensor for visual measurements was constructed using glucose oxidase (GOD), catalase (CAT) and redox dyes. Enzymes and viologen dyes were entrapped in silica gel on the inner surface of a glass tube by means of the sol-gel method. Viologen dye has blue color in its reduced form and no color in its oxidized form. First, sodium dithionite was introduced into the glass tube and viologen dye was reduced. A sample was then introduced. The color of the glass tube faded due to soluble oxygen in the sample solution, but it took more time to fade the color in the presence of glucose, because glucose oxidase and catalase, which were entrapped in the gel, consumed soluble oxygen. Based on the color fading time or the color fading length, the glucose in sample solution was quantified. The quantification range was between 0.1 and 10 µM and the RSD was within 4%. The fading color simulation of this sensor was programmed and performed. The simulation results were compared with the experimental data.

Keywords : visual measurement; glucose biosensor; sol-gel entrappment.

Effect of highly concentrated sucrose and urea in aqueous solution

Kenji Izumoto¹, Megumi Kasuno¹, Yumi Yoshida¹ and Sorin Kihara¹

(Received 23 May 2003, Accepted 13 June 2003)

Voltammograms for transfers of various ions from an aqueous solution, W, to 1,2-dichloroethane, DCE, in the presence of highly concentrated sucrose (up to 2.4 mol dm^-3) or urea (up to 9.8 mol dm^-3) in W were successfully recorded by employing a micro W|DCE interface. It was found based on the analysis of voltammograms observed that the highly concentrated sucrose or urea gave considerable influences on the diffusion of alkylsulfonate, alkali metal, alkaline earth metal or halide ions and the long-distance interaction between an ion and water. This result could be attributed to the effect of sucrose or urea on the viscosity and the relative dielectric constant of W. On the other hand, the Stokes radius of an ion in W, the formation energy of a cavity to dissolve a neutral molecule in W and the short-distance interaction between an ion and water molecules were not significantly influenced by sucrose or urea added in W, which does not support the view that sucrose or urea works as a structure-forming or -breaking agent, respectively. It was also found that the effect of urea on the denaturation of a protein in W was similar to that on the formation energy of a cavity in W.

Keywords : voltammetry for ion transfer; micro aqueous|organic interface; highly concentrated sucrose or urea; water structure; hydration of an ion.

Silver ion sensing using π-coordinate aromatic neutral carriers for soft metal ions

Norio Yoshioka¹, Setsuko Yajima¹ and Keiichi Kimura¹

(Received 8 May 2003, Accepted 18 June 2003)

We have been studying neutral carriers of ion-selective electrodes (ISEs) for soft metal ions, and have reported that π-coordinate calixarene derivatives are useful for detecting soft metal ions selectively. In this study, in order to investigate what structures are essentially needed for detecting soft metal ions, several π-coordinate aromatic compounds were chosen as neutral carriers of ISEs, and the ion sensor properties were examined. An ¹H-NMR study showed that t-butylcalix[4]arene tetra(allyl ether) and [2.2.2]-paracyclophane interact with silver ions powerfully, and that only t-butylcalix[4]arene interacts with thallium ions. Therefore, ISEs based on [2.2.2]-paracyclophane exhibited excellent silver ion sensor properties.

Keywords : ion-selective electrodes; soft metals; π-coordinate aromatic compounds.

Determination of alkylphenols and bisphenol A in sea environment by GC/MS

Rie Hando¹, Mitsuru Abo¹ and Akira Okubo¹

(Received 8 May 2003, Accepted 18 June 2003)

A sample preparation for the determination of alkylphenols and bisphenol A in surface seawater by GC/MS were studied. We improved the methods for the conditioning and elution of solid-phase extraction (SPE) in order to obtain accurate values by an easier method. We devised a method for conditioning the absorbents in order to prevent contamination from the used water. The error was less than 1 percent compared with that of the usual conditioning method. We designed an elution method in which the dispersion is small and the recovery is better than that for many other reported methods. We measured the surface water in Tokyo Bay and off the coast of Chiba. In Tokyo Bay, nonylphenol (mix) and bisphenol A were detected from tens to hundreds ng/l. The results of measurements of the surface water off the coast of Chiba showed that the concentrations of the subject compounds were no more than one tenth compared with samples from Tokyo Bay, although several subject compounds were detected.

Keywords : endocrine disruptors; bisphenol A; nonylphenol; seawater; GC/MS.

Fabrication of a centrifugal liquid membrane cell for a direct spectroscopic measurement of electrolytic reaction in two-phase liquid-membrane system

Naoko Sasaki¹, Hideaki Monjushiro¹ and Hitoshi Watarai¹

(Received 8 May 2003, Accepted 23 June 2003)

We studied the fabrication of a new centrifugal liquid membrane (CLM) cell with two electrodes, which can be used in electro-spectrochemical measurements for liquid/liquid two-phase systems. Two fabrication methods for preparing the electrodes, the chemical plating of Au and the sticking of Pt foils (width 5 mm, thickness 20 µm) on the inner surface of the CLM cell, were examined. It was elucidated that a CLM cell with Pt foils worked well as an electrochemical cell. To evaluate the CLM-electrode system, the electrolytic reduction of water-soluble porphyrin (Mn^IIITPPS) was examined. A controlled-potential electrolysis was carried out while rotating the CLM cell, and the UV-visible spectra were recorded. The electrolytic reduction of Mn^IIITPPS was successfully observed as a change in the absorption spectrum. The spectral changes with electrolysis were observed under two conditions: with a single aqueous solution and an aqueous solution/n-dodecane two phase system. It is concluded that the new CLM cell with Pt electrodes has a good ability to perform electro-spectrochemical measurements for liquid/liquid two-phase systems.

Keywords : centrifugal liquid membrane method; electrolysis; manganese-porphyrin; spectroelectrochemistry.

Phosphate-selective electrode using bis(pentafluorobenzyl)tin(IV) dibromide as carrier

Yasumasa Goto¹, Kumiko Miyazaki¹, Hiroyuki Hattori¹ and Akio Yuchi¹

(Received 6 May 2003, Accepted 24 June 2003)

Bis(pentafluorobenzyl)tin(IV) dibromide was synthesized as a novel ionophore having a relatively high Lewis acidity. The performance of this ionophore as a carrier of a phosphate ion-selective electrode was strongly dependent on the membrane solvent. Using a mixture of DOS and DMF as a membrane solvent, a larger potential slope (-70.8 mV/decade), a lower detection limit (10^-5 mol dm^-3), and a higher selectivity were obtained at a lower pH of 3, compared with the parent compound, bis(benzyl)tin dichloride. An increase in carrier concentration in the membrane phase did not change the potential response but elongated the life time of the electrode.

Keywords : ion-selective electrode; phosphate; organotin(IV) compound.

Formation reactions and photophysical parameters of highly luminescent lanthanoids(III) complexes with 4-hydroxypyridine-2,6-dicarboxylic acid

Nobuyuki Takahashi¹, Shingo Saito² and Hitoshi Hoshino¹

(Received 12 May 2003, Accepted 25 June 2003)

For the purpose of finding ligand designing strategy for lanthanoids energy-transfer luminescence, formation reactions of 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid, CDA) with terbium(III) and europium(III) ions in aqueous solution were investigated. A luminescent complex species having 1:3 stoichiometry was formed at pH 8.4~11.6. Those complexes were hydrolyzed by more alkaline solution. The relative quantum yield of Tb(III)-CDA complex at pH 11.6 was 0.636 (λ_em=544 nm) on a quinine sulfate basis. The luminescence lifetimes of Tb(III)-CDA were calculated as 1.02 ms at pH 8.4 and 1.55 ms at pH 11.6. The luminescence intensities of Tb(III) and Eu(III)-CDA complexes increased from pH 9 to 11 with the deprotonation degree of the 4-hydroxyl group on the complexes. The deprotonated Ln(III)-CDA complex species possibly has a resonance structure of the pyridone type, which would contribute to the highly enhanced luminescence intensity. Detailed photophysical data in terms of photoexcitation and the triplet energy level (low temperature phosphorescence) are given.

Keywords : energy-transfer luminescence; terbium; europium; complex; chelidamic acid.

Determination of trace amounts of aluminum in drinking water by reversed-phase ion-pair HPLC with spectrophotometric detection

Maki Iwano^1,2, Ayumi Hirano^1,3, Atsuko Nishigaki¹ and Masami Shibukawa¹

(Received 8 May 2003, Accepted 26 June 2003)

A reversed-phase ion-pair high-performance liquid chromatographic method for the determination of trace amounts of aluminum was developed using 5-sulfo-8-quinolinol as a pre-column derivatization reagent for spectrophotometric detection. All of the experiments were carried out in a class-100 clean room to avoid the contamination of aluminum from the laboratory environment. The calibration curve of aluminum standard solutions was linear over the range of 0.5~100 ppb with a correlation coefficient of 0.997 and relative standard deviations of 0.49~1.65%. The limit of detection, defined as three-times the standard deviation of the blank signal, was found to be 0.05 ppb. This method was successfully applied to the determination of trace levels of aluminum in several commercial drinking water and tap water samples.

Keywords : aluminum; HPLC; 5-sulfo-8-quinolinol; absorptiometric detection; drinking water.

Solvent extraction of platinum(II) with 1,3-dimethyl-2-thiourea and Bromocresol Green

Yoko Terada¹, Akemi Harada², Keiitsu Saito¹, Satomi Murakami¹ and Akihiko Muromatsu¹

(Received 9 May 2003, Accepted 27 June 2003)

The extraction behavior of platinum(II) with 1,3-dimethyl-2-thiourea (DMTU) from a chloride solution was studied. Bromocresol Green ion as a counter anion and 1,2-dichloroethane as an extraction solvent were used. Because the maximum absorbance was observed at a wavelength of 413 nm, the extraction efficiency was followed by a measurement of the absorbance at 413 nm of the organic phase. Because the extraction rate of platinum(II) with DMTU was fast, platinum(II) was quantitatively extracted into 1,2-dichloroethane within 15 min. The effects of the pH, the DMTU concentration and the chloride concentration on the extraction of platinum(II) were examined. The constant and maximum absorbance were obtained over the pH range from 3.3 to 4.2. A constant absorbance was obtained at more than 0.02 M DMTU, and the chloride ion concentration did not affect the extraction of platinum(II) at below 0.5 M. In order to apply to the spectrophotometric determination of platinum(II), the interferences of eight kinds of metal ions and three kinds of anions were examined. Sulfate, nitrate, perchlorate, cobalt(II) and nickel(II) did not interfere. The interferences from manganese(II), copper(II), zinc(II), palladium(II), silver(I) and cadmium(II) were found to be depressed by extraction separation with 1,5,9,13-tetrathiacyclohexadecane (TTCH) and the addition of EDTA.

Keywords : solvent extraction; 1,3-dimethyl-2-thiourea; platinum(II); Bromocresol Green.

Solvent extraction mechanism of 2-(2-pyridylazo)-1-naphthol-4-sulfonate and its divalent metal complex anions with tetrabutylammonium cation using 1-nonanol/octane mixed solvents

Takahiro Uchida¹, Takashi Yasui¹, Tetsuyoshi Naito² and Hiromichi Yamada¹

(Received 12 May 2003, Accepted 2 July 2003)

From the standpoint of the development of a less toxic solvent, the ion-pair extraction of 2-(2-pyridylazo)-1-naphthol-4-sulfonate(α-PAN-4S anion: HL^- and L^2-), its metal(II) complex anions(ML₂^2-: M = Fe(II), Ni(II), Cu(II), and Zn(II)) and 2-(2-pyridylazo)-1-naphthol-6-sulfonate(α-PAN-6S anion: HL^- and L^2-) with tetrabutylammonium cation(Q⁺) using the 1-nonanol/octane mixed solvent were carried out at 25°C . The partition and stepwise formation constants of respective ion-associates were determined according to an analysis of the respective extraction equilibria. The ion-pair formation constants on the sulfonate substituent with tetrabutylammonium cation in the aqueous phase were found to be dependent on the concentration of 1-nonanol in the mixed solvent, but those on the naphtholate to be independent of it. The partition constant(log K_D) of each ion-pair was found to increase linearly with the concentration of 1-nonanol in the mixed solvents. With respect to the ion-pair, (Q⁺)₂·ML₂^2-, the slope of the plots of log K_D against [ROH]_o increases in the order: Q₂·FeL₂ < Q₂·NiL₂ < Q₂·CuL₂ ≤ Q₂·ZnL₂. This suggests that the affinity of the ion-pair to 1-nonanol increases in this order. The difference between the respective partition constants was observed to increse with increasing the concentration of 1-nonanol for each ion pair, (Q⁺)₂·ML₂^2-. To the contrary, it was found to become smaller with decreasing the concentration of 1-nonanol, and can be expected to become vanishingly small in the pure octane solvent systems.

Keywords : stepwise formation constant of ion-pair; mechanism of ion-pair extraction; 1-nonanol/octane mixed solvent; α-PAN-4S; tetrabutylammonium cation.

Highly sensitive determination of maltooligosaccharides by HPLC with Chemiluminescence

Tomokazu Kato¹, Kimihiko Abe¹, Kazumi Nakamura¹, Masaki Tachibana¹, Hitoshi Koizumi¹, Kazue Tani¹ and Nobutoshi Kiba¹

(Received 6 May 2003, Accepted 7 July 2003)

Glucose (G1) and maltooligosaccharides (G2~G7) were separated by reversed phase liquid chromatography (RPLC) with C30 stationary phase using McIlvaine's buffer solution (pH 5.0) as mobile phase and determined with immobilized enzyme post-column reactors followed by chemiluminometric detection. The oligosaccharides were hydrolyzed to glucose by an immobilized amyloglucosidase column reactor and then the glucose produced was oxidized by an immobilized pyranose oxidase column reactor. The hdrogen peroxide formed was detected by measuring chemiluminescence emitted on admixing with luminol in an immobilized peroxidase packed flow cell. Anomers of G3~G7 were separated and α- and β-anomer peaks for each oligosaccharide were identified by using glucose oxidase reaction. The detection limits (S/N=3) for G1, G2, G3, G4,G5, G6 and G7 were 8, 8, 8, 10, 10, 300 and 500 nM (20 µl sample), respectively. The RPLC system was applied to the determination of maltooligosaccharides in a soft drink.

Keywords : C30 stationary phase; maltooligosaccharides; HPLC; immobilized enzymes; luminol chemiluminescence; anomer.

Pretreatment and preconcentration methods for hydroxylamine in environmental water samples using solid-phase extraction, followed by a spectrophotometric determination

Ryoko Fukumori¹, Yukiko Senga², Minoru Okumura¹, Kaoru Fujinaga¹ and Yasushi Seike¹

(Received 9 May 2003, Accepted 7 July 2003)

Hydroxylamine has been determined by combining oxidation to nitrite with iodine and the usual Griess-Romijin method. This iodine oxidation technique, however, has been inapplicable to the determination of hydroxylamine in environmental water due to interferences from nitrite and salinity. We developed a pretreatment method for determining hydroxylamine in environmental water based on the above-mentioned technique. Nitrite in a water sample was converted to a red azo dye with sulfanilic acid (diazo component) and N-1-naphthyletylenediamine (coupling component); the azo dye was then removed using a Sep-Pak C₁₈ cartridge. We thus prepared a nitrite-free water sample. On the other hand, the interference from the salinity was solved by adding artificial seawater to sample to enhance the salinity to greater than 5‰. The salinity in a standard solution of hydroxylamine for a calibration curve was also prepared using the standard solution with >5‰. In addition, the proposed method using a Sep-Pak C₁₈ cartridge was applicable to concentrate azo dye derived from hydroxylamine in water samples.

Keywords : spectrophotometric determination of hydroxylamine; pretreatment method; iodine oxidation; Sep-Pak C₁₈ cartridge; environmental water; brackish water.

Design of a polymer inclusion membrane having proton-ionizable polyether carriers and their separation function for lead ion

Ryotaro Hayashi¹, Takashi Hayashita¹, Takashi Yoshikawa², Kazuhisa Hiratani³, Richard A. Bartsch⁴ and Norio Teramae¹

(Received 9 May 2003, Accepted 11 July 2003)

The selective proton-driven transport of Pb²⁺ ion by novel polymer inclusion membranes (PIMs), which were composed of cellulose triacetate (CTA) as a membrane support, o-nitrophenyl octyl ether (NPOE) as a membrane plasticizer, and proton-ionizable polyethers 1~6 bearing different alkyl chain lengths from heptyl to hexadecyl as a metal ion carrier, were carried out. Due to a low solubility in NPOE, the PIMs with carriers 5 and 6 having dodecyl and hexadecyl chains exhibited no transportability for both Pb²⁺ and Cu²⁺. On the other hand, the selective transport of Pb²⁺ over Cu²⁺ was noted for PIMs with carriers 1~4. To elucidate the transport mechanism, the contribution of several factors, such as the membrane thickness, source-phase pH, carrier concentration in the membrane, and source solution concentration to the Pb²⁺ and Cu²⁺ ion flux across the PIM were examined. These factors were found to be well described by an analysis based on a carrier-mediated transport mechanism. The observed diffusion coefficient of a Pb²⁺ complex with 2 was 7×10^-12 m² s^-1, which was comparable with that of metal complexes with crown ether carriers in a NPOE-based liquid membrane. The transport selectivity of the PIM with 2 was Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺, which was consistent with the extraction selectivity of 2. The superior durability of CTA-based PIM compared with poly(vinyl chloride)-based PIM was confirmed by replicate experiments. The durability of CTA-based PIM was also supported by a scanning electron microscope analysis.

Keywords : polymer inclusion membrane; proton-ionizable polyethers; lead ion separation; carrier-mediated transport mechanism; membrane durability.

Detection of tetramethylthiuram disulfide and related compounds using the chemiluminescence of tris(2,2'-bipyridyl)ruthenium(III) cation

Nobumitsu Niina¹, Hitoshi Kodamatani², Keiitsu Saito² and Shigeo Yamazaki¹

(Received 8 May 2003, Accepted 12 July 2003)

The chemiluminescence (CL) of tris(2,2'-bipyridyl)ruthenium(III) cation was applied to the determination of tetramethylthiuram disulfide (TMTD). In this work, a sample was injected to an HPLC system with Chromolith Performance RP-18e. The elueted sample and CL reagent were mixed, and sent to a CL-detector. The detection limit of TMTD using the HPLC system was 0.15 pmol (S/N=3). The calibration curve was linear over the injection amount range from 0.6 to 20 pmol. To improve the sensitivity of the CL method, the water that generated the background was removed from the system. As a result, the sensitivity was improved.

Keywords : ruthenium; chemiluminescence; thiuram; background; nonaqueous.

Effect of metabolic inhibition against CYP3A4 by catechins in bottled green tea drinks

Takumi Nakamura¹, Emi Asada¹, Yoshiko Nagata¹ and Hideko Kanazawa¹

(Received 12 May 2003, Accepted 12 July 2003)

Catechins, major polyphenol constituents of green tea, are well known because of their antioxidant activity and chemopreventive effects against cancers. We determined catechins (catechin (C), epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG) and gallocatechin gallate (GCG)) in bottled green tea drinks. The effects of temperature on the conversion of EGCG to GCG by a heat treatment were examined. The epimerization reaction seemed to proceed slowly around 80°C, and was observed to occur rapidly at 98°C. In this study, we also investigated the effect of metabolic inhibition against CYP3A4 by individual catechins. The inhibition effects of the gallate catechins were greater than those of non-gallate catechins.

Keywords : catechins; epimerization; CYP3A4; green tea.

Liquid-liquid extraction of gallium(III) with 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol into chloroform

Hirobumi Hoshino¹, Akira Ohashi¹ and Kousaburo Ohashi¹

(Received 8 May 2003, Accepted 15 July 2003)

The extraction of gallium(III) with 8-quinolinol derivatives (HA), such as 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol (HFO₂Q) and 5-(ethoxymethyl)-8-quinolinol (HO₂Q), from a weakly acidic solution into chloroform, was investigated both in the absence and presence of 3,5-dichlorophenol (Hdcp) as a synergist. The acid-dissociation constants of HA in an aqueous solution and the distribution constants of HA between chloroform and water were determined. Although HFO₂Q has a trifluoroethoxymethyl group, which is more hydrophobic than an ethoxymethyl group, the distribution constant of HFO₂Q was found to be lower than that of HO₂Q. HFO₂Q exhibited a higher extractability toward gallium(III) than 8-quinolinol and HO₂Q. The extractability of gallium(III) with HA was enhanced upon the addition of Hdcp due to the formation of an association complex between Ga(A)₃ and Hdcp. The compositions of gallium(III)-HA complexes extracted both in the absence and presence of 3.00×10^-4~3.00×10^-2 mol dm^-3 Hdcp were assigned to be Ga(A)₃ and Ga(A)₃·nHdcp (n=1, 2), respectively. However, the formation of Ga(A)₃·2Hdcp was not observed in the HFO₂Q system, suggesting that the association of the second Hdcp with Ga(FO₂Q)₃·Hdcp was interfered by the trifluoroethoxymethyl group of HFO₂Q.

Keywords : 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol; gallium(III); liquid-liquid extraction; equilibrium constant; 3,5-dichlorophenol.

Partition coefficients of the local anesthetic dibucaine into a lipid bilayer membrane determined with a dibucaine cation sensor

Makoto Nishimoto¹, Kazuhiko Matsuoka¹, Kazuhito Nagayama¹, Takashi Hata¹, Hitoshi Matsuki³, Hiromu Satake² and Shoji Kaneshina³

(Received 8 May 2003, Accepted 17 July 2003)

Local anesthetics are known to be typical drugs which act directly on biomembranes. However, the molecular mechanism of anesthetic action is still uncertain. In order to clarity the action mechanism, the partition coefficient of anesthetics to lipid membranes is necessarily important. Most local anesthetics in clinical use are tertiary amine compounds that exist in neutral and/or positively charged species, depending on the pH of the solution. In this study, we prepared coated wire electrodes sensitive to the local anesthetic dibucaine cation, and determined the partition coefficient of anesthetics into a lipid membrane. Moreover, we focused our attention on the pH-dependence of the partition coefficient in order to elucidate the contribution of charged- and uncharged-dibucaine to the lecithin membrane/buffer partition coefficients. The lecithin membrane/buffer partition coefficient was directly determined by the dibucaine cation sensor as a function of the anesthetic concentration and the pH. The limiting partition coefficient extrapolated to infinite dilution was employed because the values of partition coefficients were dependent upon the dibucaine concentration. The limiting partition coefficient increased with an increase in the pH. This means that uncharged species increased with an increase in the pH because pK_a of dibucaine is 8.72 at 25°C. The partition coefficients of charged and uncharged dibucaine into the lecithin membranes were estimated from the pH-dependence of the limiting partition coefficients. The partition coefficients were 1.6×10⁴ and 8.6×10⁶ for charged and uncharged dibucaine, respectively. The electrodes were applied satisfactorily for determining for the partition coefficient of local anesthetic dibucaine into biomembranes.

Keywords : potentiometry; coated wire electrode; local anesthetic; lipid bilayer membrane; partition coefficient.

Changes of luminescence properties dependent on OH-impurities in natural quartz

Takahiro Yamaguchi¹, Naoki Mitamura¹, Akihiro Takeuchi² and Tetsuo Hashimoto²

(Received 16 May 2003, Accepted 18 July 2003)

The changes into TL property from quartz slice samples accompanied by a thermal treatment for 100 h at 1100°C were studied using IR absorption spectra and a measurement of the α-β transition temperature. Both BTL and weak BTL parts, having a 470 nm peak, from the original quartz slice were unexpectedly changed into an intense RTL-property, giving bands at around 380 nm and 630 nm after annealing. The distribution patterns due to OH-impurities from the IR absorption spectra showed an inverse correlation to the color center images (CCIs) and the TLCIs before the thermal treatment. The denser CC and RTL-parts appeared after annealing from the opposite BTL patterns in the original slice. A similar tendency was found concerning OSL phenomena. The α-β transition temperatures from a colorless (or weak BTL) part, corresponding to a higher impurities part, were apparently related to the prominent changes of the luminescence properties; the thermal annealing procedure brought about into 570.3°C from 571.6°C in the colorless part, while almost constant temperature of 572.5°C maintaing in color part in the original quartz slice.

Keywords : natural quartz; thermal annealing treatment; thermoluminescence; optically stimulated luminescence; Al hole center; OH-related impurity; infrared absorption spectrum; α-β transition temperature.

Molecular species analysis of phosphatidylglycerols by reversed-phase HPLC/ESI-MS

Saori Ishioka¹, Yukako Taoka¹ and Yutaka Itabashi¹

(Received 19 May 2003, Accepted 18 July 2003)

A facile method for the determination of molecular species of phosphatidylglycerols (1,2-diacyl-sn-glycero-3-phospho-1'-sn-glycerol, PG) is described. Intact PG isolated from spinach leaves and Escherichia coli IAM12119 was converted into bis(3,5-dinitrophenylurethane) derivatives, followed by reversed-phase high-performance liquid chromatography (HPLC) on an ODS column (25 cm×4.6 mm i.d., 5 µm particle size) using methanol/water/aqueous ammonium hydroxide (95:5:0.1 or 93:7:0.1, v/v/v) as the mobile phase, which gave clear resolution of individual molecular species containing saturated and unsaturated fatty acids. Peaks were detected at 254 nm UV. Reversed-phase HPLC in conjunction with negative electrospray ionization mass spectrometry (ESI-MS) gave a weak [M+2H–bis-DNPU–RCO]^- ion in addition to a prominent pseudomolecular [M–H]^- ion, by which individual molecular species could be identified.

Keywords : phosphatidylglycerol; molecular species; 3,5-dinitrophenylurethane; spinach leaves; Escherichia coli; reversed-phase HPLC; electrospray ionization mass spectrometry.

Synergistic extraction of lanthanoids(III) with 2-thenoyltrifluoroacetone and triphenylphosphine oxide and hydration of the extracted species

Shin-Ichiro Yorikuni¹, Yasunori Makita¹, Izuru Matsubayashi¹ and Yuko Hasegawa¹

(Received 14 May 2003, Accepted 19 July 2003)

Lanthanoids(III) were extracted from a 0.1 M (1 M=1 mol dm^-3) NaClO₄ aqueous solution into chloroform with 2-thenoyltrifluoroacetone (TTA, HA) and triphenylphosphine oxide (TPPO, B). By analyzing the extraction data, the formation constants, (β_n=[LnA₃·nB]_o[LnA₃]_o^-1[B]_o^-n, n=1 and 2), were determined. The hydration number of the complexes prepared by solvent extraction was also determined across the lanthanoid series. The results suggest that since more than two water molecules are released from LnA₃ on the first complexation with TPPO, the heavier lanthanoids(III) do not possess any water molecules to be released upon the second complexation. Accordingly, the second complexation should be less favorable entropically. This should contribute to the values of the formation constants of the second complex to be smaller along with increasing the lanthanoid atomic number.

Keywords : lanthanoid(III); synergistic extraction; triphenylphosphine oxide; 2-thenoyltrifluoroacetone; hydration number.

Synthesis of dithiocarbamate-chitosan resin and its adsorption behavior for trace metals

Takahiko Ninomiya¹, Koji Oshita¹, Mitsuko Oshima¹ and Shoji Motomizu¹

(Received 8 May 2003, Accepted 22 May 2003)

A chitosan-based resin possessing the dithiocarbamate moiety (DTC-chitosan resin) was synthesized using cross-linked chitosan as a base material. The adsorption behavior of trace metal ions on the DTC-chitosan resin was systematically examined by packing it in a mini-column (1 ml of the resin) and measuring the recovery by ICP-MS. The resin could adsorb almost 100% of 7 kinds of metals(Cu, Mo, Ag, Te, W, Hg and Bi) at pH ranges from acidic to neutral. However, elution of these metals from the resin was difficult. In this study, we improved the recovery efficiency by a pretreatment of the resin: the resin was added to 100 ml of a 0.1 M copper sulfate solution, stirred for 24 h and washed sufficiently with 1 M nitric acid and water. With this pretreatment, metals adsorbed on 1 ml of the resin were readily eluted with 1 M nitric acid (10 ml). This method was applied to the determination of metals in river-water samples; the RSDs (10-fold preconcentration) were within 5%.

Keywords : chitosan resin; dithiocarbamate; heavy metals; elution method; preconcentartion.

Technical Papers

Simultaneous determination of residual chlorine and other anions in water by ion chromatography

Li Hui¹, Makoto Nonomura^1,2 and Noriko Itoh¹

(Received 8 May 2003, Accepted 16 July 2003)

An ion chromatographic method (IC) has been studied to determine residual chlorine and other anions in water simultaneously using a conductivity detector. It is based on the formation of chloramine-T by the reaction of residual chlorine and a p-toluenesulfonamide aqueous solution, followed by the conversion of chloramine-T to cyanogen chloride with potassium cyanide. Cyanogen chloride is then oxidized to cyanate ion at 25°C for 10 min. Because cyanate ion (pK_a=3.66) can be measured by IC with a conductivity detector, residual chlorine can be determined indirectly from the peak area of the cyanate ion. The cyanate ion is stable for 4 hours, with no inferences from Cl^-, NO₃^- or SO₄^2-. A linear relationship between the concentration of residual chlorine and the peak area of cyanate ion was obtained in the concentration range of 0.02 to 2 mg Cl₂ l^-1. The relative standard deviation (RSD) was about 3.56% (n=5) for 0.1 mg Cl₂ l^-1. The proposed method was applied to the determination of residual chlorine in tap water and compared with diethyl-p-phenylenediamine (DPD) spectrophotometry. An exceptionally good agreement was obtained.

Keywords : ion chromatography; residual chlorine; anions; tap water; p-toluenesulfonamide; chloramine-T; potassium cyanide; cyanogen chloride; cyanate ion.

Notes

Solid-phase extraction and concentration of trace chlorophenols with extractant- impregnated membrane disks

Takayuki Wakui¹, Hisanori Imura¹ and Kousaburo Ohashi¹

(Received 4 April 2003, Accepted 6 May 2003)

The solid-phase extraction and concentration of mono-, di-, and tri-chlorophenols (CPs) were studied using trioctylphosphine oxide (TOPO)- and trioctylmethylammonium chloride (TOMAC)-impregnated membrane disks (Empore^TM). The solid-phase extraction of CPs at a pH lower than 7 was markedly enhanced with TOPO, and became almost quantitative. This extraction enhancement is ascribed to hydrogen bonding between TOPO and CPs in the solid phase. The extraction of CPs under the basic conditions was markedly enhanced with TOMAC. A quantitative recovery of CPs at pH 2.9~10.3 was achieved using both TOPO and TOMAC-impregnated membrane disks. To determine CPs by HPLC, they were eluted by acetonitrile containing NH₃, evaporated to dryness in the presence of LiOH, and dissolved in a small volume of acetic acid. Trace CPs at 0.1 µg l^-1 levels were readily concentrated by a factor of 500 and quantitatively recovered.

Keywords : solid-phase extraction; chlorophenols; membrane disk; TOPO; TOMAC.

Visual determination of sulfate ion using the heterogeneous filtration of the precipitate on a black membrane filter

Keisuke Morita¹, Junichi Isoe¹ and Emiko Kaneko¹

(Received 6 May 2003, Accepted 13 June 2003)

The measurement of sulfate ion is important in environmental and industrial fields. However, a field-analytical method which can be implemented in field testing and performed at the site is still lacking. Therefore, the development of a sensitive, yet simple technique is needed for the field determination of sulfate ion. In this study, a simple visual method has been established for the determination of sulfate ion at ppm levels using a black membrane filter. Our method consists of two steps: barium chloride is added to a water sample to form barium sulfate, and the mixture containing the white precipitate is filtrated through a black membrane filter using a 10 ml syringe. We found that the precipitate is effectively concentrated in a distinct pattern on the membrane filter, which is a tracing of the reverse side of the support screen. Sulfate ion as low as 2 ppm concentrations can be visually detected when a 10 ml sample is used. The method reported here will be useful as a simple and rapid field test, which has long been in great demand.

Keywords : sulfate ion; visual detection; membrane filter; precipitate.

Changes in the cellular components of sugar beet under salt stress

Fusa Matsuzaki¹, Jinghua Zhang¹, Yuji Takao¹, Takashi Shimomachi¹ and Sunao Yamazaki¹

(Received 30 April 2003, Accepted 15 June 2003)

The acclimation of a plant to a constantly changing environment involves the accumulation of certain organic compounds of low molecular mass, known collectively as compatible solutes, in the cytoplasm. Evidence from numerous investigations of plants strongly suggests that glycine betaine (GB), an amphoteric quaternary amine, plays an important role as a compatible solute under various types of environmental stress, such as high levels of salts and low temperature. In this work, sugar beet (Beta vulgaris) was grown at NaCl concentrations of up to 300 mmol/l soil, and the effects of salt on the growth, contents of water, chlorophyll, soluble protein, soluble saccharide and GB in leaf were measured. The addition of NaCl up to 300 mmol/l soil significantly affected the growth, and the contents of water and chlorophyll decreased, whereas the soluble protein and saccharide concentrations in the leaf changed little. On the other hand, the GB concentration increased 6-fold with increasing the salinity of the medium, suggesting that GB is a main osmoprotectant in this plant. The induction of GB was monitored by cultivating the plant seed under salt stress. It was found that the GB originally contained in the seed was lost during the early stage of cultivation, and new GB was synthesized in the stage of germination in a dose-dependent fashion with respect to the salt concentration.

Keywords : Beta vulgaris; capillary electrophoresis; glycine betaine; salt stress; sugar beet.

Effect of substituted phenolates as a counterion on the ion-pair extraction of alkali metal ions using crown ether

Haruyoshi Nakagawa¹, Naoki Hirayama² and Takaharu Honjo²

(Received 15 April 2003, Accepted 2 July 2003)

The effect of a counterion was investigated in the solvent extraction of alkali metal ions using crown ether. Nitrobenzene was used as the solvent, 18-crown-6 was used as the extracting reagent, rubidium ion, which suits the cavity size of 18-crown-6, was selected as the model of alkali metal ions. In order to vary the distribution of the electric charge and the hydrophobicity of the counterion, various substituted phenols were used as the counterion. The maximum extraction ratio of rubidium ion was increased with non-localization of the distribution of the electric charge and with its hydrophobicity higher. The maximum extraction ratio was increased by introducing chloro substituent to the counterion, but it was not more effective than introducing nitro substituent. The pH where the extraction curve rose depended upon the pK_a of the counterion. In this extraction system, the value of the pH controlled only the condition of the dissociation of the counterion.

Keywords : counterion; ion-pair extraction behavior; alkali metal ion; crown ether.

Component analysis of a halophyte, Suaeda japonica, grown on the shore of Ariake Sea

Noriko Wada¹, Jinghua Zhang², Nobutaka Jinno³, Akira Okubo¹ and Sunao Yamazaki²

(Received 7 May 2003, Accepted 3 July 2003)

The adaptation of a halophyte, Suaeda japonica, in a saline environment was surveyed by analysing the cellular components, such as the major inorganic and organic constituents, as well as glycine betaine between halophytic and non-halophytic plants grown along the seashore of Ariake Sea. In contrast to non-halophytes, a remarkable accumulation of salt in leaf cells of halophytes, Suaeda and Artemisia, was accompanied by the accumulation of a compatible solute, glycine betaine. In a culture experiment under saline conditions, glycine betaine looked to be most effectively induced in the concentration of salt of around 250 mM NaCl.

Keywords : Ariake Sea; capillary electrophoresis; glycine betaine, halophyte; Suaeda japonica.

Analysis of fatty acids by capillary electrophoresis with indirect UV detection

Satoko Tadaumi¹, Shinobu Endo¹, Hiroto Akagawa¹ and Yutaka Itabashi¹

(Received 19 May 2003, Accepted 16 July 2003)

An analysis of the long-chain fatty acids in some saponified vegetable oils (olive, rice bran and linseed oils) and salmon roe phospholipids was carried out using capillary zone electrophoresis (CE) with indirect UV detection at 254 nm. Adenosine monophosphate (AMP) was used as an indirect UV detection reagent. The electrolyte consisted of 40 mM Tris buffer and 2.5 mM AMP in N-methylformamide/dioxane/water (5:4:1, v/v/v, for vegetable oil fatty acids; 4:6:1 for fish oil fatty acids). A satisfactory separation of an approximately 20 fmol mixture of palmitic (16:0), stearic (18:0), oleic (18:1n-9), linoleic (18:2n-6) and linolenic (18:3n-3) acids from vegetable oils was achieved within 25 min. Icosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3) were also completely resolved within 50 min, although some peak overlappings were observed in the fish sample. The fatty acid compositions (mol%) obtained by CE were in good agreement with those determined by HPLC. Thus, the CE method employed in this study would be useful for determining the composition of saturated and unsaturated fatty acids from biological samples.

Keywords : capillary electrophoresis; vegetable oil; icosapentaenoic acid; docosahexaenoic acid; fatty acid composition.

Determination of boron in steel by anion-exchange separation and ICP-AES

Toshio Shinohara¹, Hirokazu Matsubara¹, Nobutaka Yoshikuni¹ and Koichi Oguma¹

(Received 23 May 2003, Accepted 22 July 2003)

The determination of boron in steel was carried out by ICP-AES combined with anion-exchange separation. About 0.2 g of a steel sample was weighed in a quartz beaker and dissolved with a mixture of 2 cm³ of nitric acid, 1.5 cm³ of phosphoric acid and 4 cm³ of water by heating on a hot plate. Most of the nitric acid was evaporated off and the sample solution was transferred into a separatory funnel with 10 cm³ of 0.1 mol dm^-3 nitric acid and water. About 3 g of iron(III) hydroxide oxide was dissolved in a mixture of 10 cm³ of hydrofluoric acid, 1 cm³ of 30% hydrogen peroxide and 50 cm³ of water by heating on a hot plate and added to the above sample solution. The sample solution was diluted to about 100 cm³ with water, allowed to stand for 1 h and then loaded onto an anion-exchange resin Bio-Rad AG1 column preconditioned by a fluoride solution. The iron in the sample solution passed through the column, while the boron was adsorbed as BF₄^- on the column and recovered with 6.5 mol dm^-3 nitric acid. The effluent, containing boron, was treated with phosphoric, perchloric and nitric acids and diluted to 25 cm³ with water to be subjected to ICP-AES at 249.77 nm. The proposed method was successfully applied to the determination of boron in a steel-certified reference material, JSS 174-5, provided by the Japan Iron and Steel Federation. The detection limit was found to be 1.3 µg g^-1 boron in steel.

Keywords : boron; steel; anion-exchange separation; hydrofluoric acid; ICP-AES.

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