BUNSEKI KAGAKU Abstracts

Vol. 53 No. 9

September, 2004

Research Papers

Measurement and behavior analysis of hydrogen peroxide and organic peroxides in the atmosphere and rainwater

Song-nan Huang¹, Yasuro Fuse² and Etsu Yamada^1,2

(Received 30 March 2004, Accepted 2 June 2004)

The measurement of hydrogen peroxide and organic peroxides in the atmosphere and rainwater was developed, and the behavior of these peroxides affecting forests was investigated. The seasonal variation of atmospheric H₂O₂ in Kyoto (0.18~6.96 ppbv) showed a summer maximum and a winter minimum. Methylhydroperoxide (MHP) was mainly detected in the atmosphere with a level of 0.07~0.29 ppbv during June and September. Organic peroxides in the atmosphere increased above ca.25°C, and correlated with the O₃ concentration and relative humidity, while atmospheric H₂O₂ was inversely correlated with the relative humidity. They were not related to solar radiation and UV radiation. The H₂O₂ concentration in rainwater was higher than 50 µM in the summer. Hydroxymethylhydroperoxide (HMHP) and MHP as organic peroxides were detected in rainwater with low concentrations of less than 2 µM during June and August.

Keywords : hydrogen peroxide; organic peroxides; atmosphere; rainwater; behavior analysis.

Heavy-metal pollution and its state in the diatom distribution along with heavy-metal speciation in rivers at the feet of old copper mines, Ishikawa prefecture

Takashi Yamada¹, Michiaki Sumita², Yoshiaki Nakanishi¹ and Takaharu Honjo¹

(Received 18 March 2004, Accepted 4 June 2004)

In this study, we tried to solve heavy-metal pollution and its state in rivers from both chemical and biological viewpoints. The sediment (sediment on the river bed and attached substances, etc.) was taken in rivers at the feet of old copper mines, Ishikawa prefecture. Its wet ashing and sequential extraction were performed. The total copper content and the copper contents of all fractions containing the types of associations between copper and the sediment were determined. The diatom taxa, growing in attached substances on psephite, were also identified. As a result, the correlation between the ratio of the exchangeable fraction (e.g. ion-exchangeable chemical species and carbonate) to the total contents of copper and the relative abundance (as the ratio of the number of each taxon to the total number of diatom) of Achnanthes minutissima, which is specified as an indicator diatom of heavy-metal pollution, was observed. The exchangeable fraction contained toxic species of copper. It seems that they have an effect on biota containg diaton in rivers.

Keywords : heavy-metal pollution; chemical species; sequential extraction; diatom.

Photochemical formation of peroxides in coastal seawater around Okinawa Island

Hitomi Nakajima^1,2, Kouichirou Okada³, Hiroyuki Fujimura¹, Takemitsu Arakaki¹ and Akira Tanahara⁴

(Received 7 April 2004, Accepted 16 June 2004)

The photochemical formation of peroxides (hydrogen peroxide and organic peroxides) was studied in seawater collected along the coast of Okinawa Island, using a solar simulator. Our study showed that hydrogen peroxide (HOOH) was photochemically formed, but organic peroxides were not. The mean value of the HOOH photo-formation rates was 1.38±0.80 nM min^-1. We observed two types of HOOH formation kinetics, i.e. one with a constant formation rate and the other with a decreasing formation rate. Strong correlations were observed between the HOOH formation rate, the dissolved iron concentrations (R=0.75) and the absorbance of seawater samples at 300 nm (R=0.83). The dissolved organic carbon (DOC) concentrations did not show a strong correlation with the HOOH formation rate (R=0.30). It is suspected that the compositions of dissolved organic compounds collected from different sites may differ, and that the photochemical formation of HOOH is affected by the compositions of dissolved organic compounds. The salinity showed a strong negative correlation with the HOOH formation rate (R=-0.76), suggesting that major HOOH-forming chromophores originate from land.

Keywords : hydrogen peroxide; flow injection analysis; seawater; photochemistry; Okinawa.

Search for new aqueous-aqueous two-phase systems for the countercurrent chromatographic separation of proteins

Naoko Takeuchi¹, Shinya Takeshige¹, Wataru Nagatsuka¹, Heisaburo Shindo¹ and Yoichi Shibusawa¹

(Received 6 May 2004, Accepted 26 June 2004)

Several aqueous-aqueous polymer two-phase systems were searched for the countercurrent chromatographic (CCC) separation of proteins. The selective separation of ovomucin from egg white was performed by CCC using a two-phase system composed of 15%polyethylene glycol (PEG) 1540-dextran T10-100 mM potassium phosphate at pH 7.0. Ovalbumin, conalbumin and lysozyme having small partition coefficients were eluted from the column with dextran-rich lower phase as a mobile phase. On the other hand, ovomucin with the large partition coefficient showed a high affinity to the upper stationary phase. After elution of the ovalbumin, conalbumin and lysozyme, the ovomucin was collected from the column by pushing out with air. After purification, PEG 1540 and dextran T10 were easily eliminated from the CCC fractions by ultrafiltration for a short time. The proteins in the CCC purified fractions were detected by SDS polyacrylamide gel electrophoresis.

Keywords : aqueous-aqueous two-phase systems; countercurrent chromatography; egg-white proteins; partition coefficient.

Determination of hypochlorite ion by anodic voltammetry

Fumihiro Kodera¹, Minoru Umeda¹ and Akifumi Yamada¹

(Received 21 April 2004, Accepted 30 June 2004)

In this paper, the development of a new electroanalytical method based on an anodic reaction for the hypochlorite ion is described. The determination was carried out by linear sweep-voltammetry at a Pt electrode. The peak current of observed oxidation wave was proportional to the amount of hypochlorite ion. The influences of various physical and chemical factors (repeatability, supporting electrolyte, pH, sweep rate, temperature, metal ion, and dissolved oxygen) were investigated. A fairly good correlation (R²=0.987) between this method and iodometric titration was achieved for standard samples (n=5). This method seemed to be very useful to analyze the hypochlorite ion.

Keywords : hypochlorite ion; anodic voltammetry; electroanalytical method; electrooxidation; Pt electrode.

Separation of inorganic ions by high-speed countercurrent chromatography with an aqueous biphasic system

Kazuyuki Ishii¹, Yuka Tanaka¹, Kyoko Hata¹, Masaharu Goto¹, Kazunori Saitoh¹, Hiroaki Minamisawa² and Masami Shibukawa¹

(Received 13 May 2004, Accepted 30 June 2004)

The optimum experimental conditions for J coil planet centrifuge high-speed countercurrent chromatography (HSCCC) with aqueous biphasic systems consisting of polyethylene glycol (PEG) and sodium sulfate were investigated using some inorganic anions as model compounds. The PEG-rich upper phase was used as the stationary phase and the salt-rich lower phase was used as the mobile phase. In order to eliminate fluctuations of the base line of chromatograms owing to emulsification caused by excessive mixing of the two phases, water was mixed with the eluate from the column prior to UV detection. The resolution of iodate ion and iodide ion increased with an increase in the revolution speed of the Teflon tube column holder although the volume of the stationary phase retained in the column decreased. This was due to an improvement of the separation efficiency, shown as an increase in theoretical number of sample compounds. The increase in the flow rate of the mobile phase caused a decrease in the stationary phase volume. However, the resolution did not depend on the flow rate in the range studied. This may be interpreted in terms of relatively high distribution ratios of the inorganic anions used in this study. Separation of some inorganic anions and that of chromium(III) ion and chromate(VI) ion were easily accomplished by HSCCC with PEG#1000-16.7%(w/w) Na₂SO₄ aqueous biphasic system.

Keywords : high-speed countercurrent chromatography; aqueous biphasic system; inorganic ions; optimization.

Determination of anionic surfactants using newly synthesized n-dialkyl-2,2'-thiacyanine dyes

Akinori Goto¹, Mitsuko Oshima¹, Toshio Takayanagi¹ and Shoji Motomizu¹

(Received 7 May 2004, Accepted 7 July 2004)

For the spectrophotometric determination of anionic surfactants in aqueous media, cationic dyes with a 2,2'-thiacyanine skeleton were newly synthesized. Carbon numbers of 4 and 6 in the n-dialkyl chain combined at the N position of 2,2'-thiacyanine are new compounds. Fundamental information, such as the pKa values, was obtained. These two compounds and purchased diethyl- and dipropyl-2,2'-thiacyanine were examined for the spectrophotometric determination of an anionic surfactant, DBS. Of these, 3,3'-dihexyl-2,2'-thiacyanine (DHT) showed the best sensitivity. The calibration graph for DBS with DHT was linear up to 1×10^-5 M, and the detection limit was 4×10^-7 M. By a hydrophobic interaction, even a cationic surfactant, Zephiramine, and a nonionic surfactant, Triton X-100, could react with DHT. The ion-association constants for these surfactants with DHT were obtained.

Keywords : n-dialkyl-2,2'-thiacyanine dyes; surfactants; ion association; spectrophotometry.

Measurement of antioxidative activity against hypochlorite ion by sequential injection analysis with luminol chemiluminescence detection

Kuniko Nakamura¹, Yoshihito Ohba¹, Naoya Kishikawa¹ and Naotaka Kuroda¹

(Received 6 May 2004, Accepted 7 July 2004)

A sequential injection analysis (SIA) with chemiluminescence detection for measuring the antioxidative activity against hypochlorite ion was developed. The antioxidative activity was expressed as the percentage inhibition of luminol chemiluminescence due to the scavenging of hypochlorite ion by an antioxidant. Using a 50 mM borate buffer (pH 9.5) as a carrier, the SIA system was optimized with respect to the reagent concentrations, volume and flow rates. The SIA system could measure 3 samples within 4 min. The relative standard deviations of the antioxidative activity for 2 nM ascorbic acid were 2.5% (within-day, n=3) and 3.7% (between-day, n=3). Several antioxidants, such as ascorbic acid, α-tocopherol and Trolox, were successfully measured by the SIA system, and the relationships between their antioxidative activity and the logarithm of concentrations of antioxidants were linear (r=0.983-0.999). The proposed SIA system was rapid, sensitive and reproducible with minimum consumption of the reagents, and was thus useful for the rapid screening of antioxidants possessing antioxidative activity against hypochlorite ion.

Keywords : sequential injection analysis; hypochlorite ion; antioxidative activity; antioxidant; luminol chemiluminescence.

Properties of p-nitrocalix[6]arene and its reactivity with uranyl ion

Makiko Kajiwara¹, Masashi Nishida¹ and Isao Yoshida¹

(Received 30 April 2004, Accepted 8 July 2004)

The complex formation reaction of p-nitrocalix[6]arene, CALX-N6, with a uranyl ion, UO₂²⁺, was studied by the pH titration method in a 20%acetone aqueous solution at 20°Cand m=0.01. From the absorption data of CALX-N6, the acid dissociation constants were determined to be as follows: pK_a1=2.72, pK_a2=5.71 and pK_a3=11.5₉. These results indicate that CALX-N6 is a relatively strong tri-protonic acid, H₃L, which releases 3 mol of protons from 1 mol of CALX-N6, having 6 mol of hydroxyl groups, in a weakly acidic to an alkaline solution. CALX-N6 formed four 1:1 complex species with UO₂²⁺. From the pH titration data for the CALX-N6 - UO₂²⁺ mixture solution, the log overall stability constants, logβ_mlh, of these 1:1 complexes were determined to be as follows: 17.3 for 111 (UO₂LH), 12.1 for 110 (UO₂L^-), 7.27 for 11-1 (UO₂LH_-1^2-) and 1.08 for 11-2 (UO₂LH_-2^3-) where β_mlh=[(UO₂)_mL_lH_h]/([UO₂]^m[L]^l[H]^h). These acid-dissociation and complex-formation behaviors of CALX-N6 to UO₂²⁺ are similar to the case of water-soluble calix[6]arene-p-sulfonate, CALX-S6, which is a super uranophile.

Keywords : p-nitrocalix[6]arene (CALX-N6); acid-dissociation constants; stability constants; uranyl ion; pH titration.

Rapid separation on monolithic silica-based capillary columns in LC

Atsushi Suzuki¹, Hideyuki Uzu¹, Shinichi Masuoka¹, Xiong Li¹, Lee Wah Lim¹ and Toyohide Takeuchi¹

(Received 4 May 2004, Accepted 8 July 2004)

Monolithic silica capillary columns have an advantage over conventional densely packed columns in terms of their higher permeability. The inlet pressure and the column length have been optimized. By applying moderate inlet pressures, benzene and five kinds of alkylbenzenes could be separated on a monolithic ODS-bonded silica capillary column within one minute.

Keywords : capillary LC; monolithic silica columns; rapid separation; alkylbenzenes.

Properties of dendritic and cyclic thiourea derivatives as neutral carriers for anion sensors

Sachie Uchida¹, Yuichiro Komatsu¹, Hitomi Satoh¹, Setsuko Yajima¹, Keiichi Kimura¹, Yoshito Tobe², Shin-ichi Sasaki², Masaaki Mizuno², Yohei Watanabe² and Keiji Hirose²

(Received 7 May 2004, Accepted 8 July 2004)

We desinged seven neutral carriers for hydrophilic anion sensors: four compounds containing one thiourea group and dendritic benzyl ether derivatives, two compounds containing three or four thiourea groups, and a cyclic compound containing three thiourea groups. The association constants with dihydrogen phosphate ion for these thiourea derivatives were determined in organic solvents. The compounds exhibited high association constants with dihydrogen phosphate ion. When these compounds were used as neutral carriers of ion-selective electrodes (ISEs) for phosphate ion, the slopes of the EMF responses were very small in all cases. The ISEs showed better EMF responses for sulfate ion than for phosphate ion. Especially in the case that dendritic and cyclic derivatives containing three thiourea groups were used as neutral carriers, the ISEs exhibited excellent EMF responses for sulfate ion and anion selectivities.

Keywords : anion-selective electrodes; dendritic and cyclic thiourea derivatives; neutral carriers; sulfate ion.

Comparison of elution behavior of catechins in high-performance liquid chromatography with that on high-speed countercurrent chromatography

Atsushi Shoji¹, Akio Yanagida¹, Heisaburo Shindo¹ and Yoichi Shibusawa¹

(Received 7 May 2004, Accepted 10 July 2004)

Reversed-phase (RP) partition chromatographic separations of eleven kinds of catechins were performed by HPLC using on ODS monolith column and by high-speed countercurrent chromatography (HSCCC) with a two-phase solvent system composed of t-butylmethylether/acetonitrile/0.1% trifluoroacetic acid (2:2:3). Procyanidin C1 (PC1; trimeric epicatechin) was strongly retained to the ODS column of RP-HPLC in spite of its smallest value of the octanol/water partition coefficient (log P) among the catechins tested. On the other hand, the retention time of each catechin upon RP-HSCCC separation was decreased with decreasing value of log P. Thus the most hydrophilic oligomer, such as PC1, was first eluted from the RP-HSCCC column.

Keywords : monolith ODS column; high-speed countercurrent chromatography (HSCCC); catechin; procyanidin; log P.

Spectrofluorometric determination of pyrophosphoric acid by utilizing condensation reaction between resorcinol and propionaldehyde

Sanae Ota¹, Takako Yamaguchi¹ and Yoshikazu Fujita¹

(Received 6 May 2004, Accepted 12 July 2004)

A simple and sensitive spectrofluorometric method for the determination of pyrophosphoric acid, whose role is presumed to be a catalyst-like action, was established by utilizing condensation reaction between resorcinol and propionaldehyde. The calibration graph has good linearity over 0.007~1.4 µg pyrophosphoric acid in 10 ml of the final solution, by measuring the fluorescence intensities of the sample and blank solutions at an emission wavelength of 457 nm with an excitation wavelength of 380 nm, respectively. The relative standard deviation for five replicate determinations of 0.14 µg of pyrophosphoric acid was 1.25%.

Keywords : spectrofluorometry; pyrophosphoric acid; condensation reaction; resorcinol; propionaldehyde.

Development of rotating liquid membrane disk electrode and rotating liquid membrane ring-liquid membrane disk electrode and evaluation of characteristics of ion transfer reactions at the rotating aqueous | organic solution interface

Kentaroh Fujii¹, Shuhei Tanibuchi¹ and Sorin Kihara¹

(Received 1 June 2004, Accepted 13 July 2004)

A liquid membrane disk electrode, LMDE, and a liquid membrane ring-liquid membrane disk electrode, LMRE-LMDE, were developed by placing a solidified polyvinyl chloride thin membrane impregnated with 2-nitrophenyl octyl ether, NPOE-LM, on the surface of a glassy carbon, GC, disk or ring electrode. A couple of redox reagents and a supporting electrolyte were added into NPOE-LM. The voltammogram for the ion transfer at the interface between an aqueous solution, W, and NPOE-LM was recorded by setting the developed electrode in W and rotating at a rate, ω, between 0 and 4000 rpm. Though there exist two interfaces (W NPOE-LM and NPOE-LM GC interfaces) in the liquid membrane electrode system, the reaction at the objective W NPOE-LM interface could be analyzed when the NPOE-LM GC interface was depolarized by redox reactions of reagents of rather high concentrations added in NPOE-LM. The sensitivity of the ion-transfer current at the W | NPOE-LM interface, I, was enhanced to be more than 100 times better when LMDE was rotated at ω higher than 200 rpm. For examples, the limiting currents, I_l, at LMDE observed for the transfer of tetraethylammonium ion, TEA+, from W to NPOE-LM and that for the transfer of K⁺ from W to NPOE-LM facilitated by dibenzo-18-crown-6 added in NPOE-LM were proportional to concentrations of TEA⁺ and K⁺, respectively, in W in the range between 10^-7 and 2×10^-6 mol dm^-3 when ω was 1000 rpm. The standard deviation determined by 5 repeated measurements of I_l for 10^-6 mol dm^-3 TEA⁺ was 3.2%. The reversibility of the ion transfer reaction could be evaluated based on the dependence of I on ω of LMDE, and the reaction product at LMDE could be identified at LMRE when rotating LMRE-LMDE system was adopted.

Keywords : liquid membrane disk electrode; liquid membrane ring-liquid membrane disk electrode; aqueous | 2-nitrophenyl octyl ether interface; ion transfer; sensitivity; reaction process.

Simultaneous separation of traces of cobalt, nickel, and copper from an aluminum matrix with an emulsion containing mixed ligands for graphite-furnace atomic absorption spectrometry

Motonori Nakao¹, Hiroaki Matsumiya¹ and Masataka Hiraide¹

(Received 28 April 2004, Accepted 20 July 2004)

Water-in-oil (w/o) type emulsions were prepared by dissolving 0.10 mmol of chelating agent and 0.03 ml of non-ionic surfactant Span-80 in 2.0 ml of toluene and vigorously mixing with 0.5 ml of 1.0 mol l^-1 hydrochloric acid by ultrasonic irradiation. The resulting emulsions were gradually injected into 25 ml of sample solution and dispersed by stirring as numerous tiny globules. Traces of heavy metals (e.g. Co, Ni, and Cu) were diffused through the toluene layer into the small droplets of hydrochloric acid encapsulated in the emulsion. When thenoyltrifluoroacetone was employed as a chelating agent, the recovery of cobalt and nickel increased synergistically with the addition of 1,10-phenanthroline into the toluene layer, allowing the quantitative collection of these metals at pH 4. At this pH, the present emulsion enabled the simultaneous separation of cobalt, nickel, and copper from an aluminum matrix, and was successfully employed as a separation medium for the determination of these metals in high-purity aluminum and alumina by graphite-furnace atomic absorption spectrometry.

Keywords : emulsion; synergistic effect; thenoyltrifluoroacetone; 1,10-phenanthroline; determination of cobalt, nickel and copper in aluminum samples.

Electrochemical characterization of Pt/C and a polyelectrolyte complex-based catalyst layer

Syunsuke Kawaguchi¹, Masaya Kamada¹, Akifumi Yamada¹ and Minoru Umeda¹

(Received 6 May 2004, Accepted 20 July 2004)

The electrocatalyst layer of polymer electrolyte fuel cells(PEFCs) formed a three-phase interface by using a mixture of Pt/C and a proton-conductive polymer. In the case where Nafion was used as a proton-conductive polymer, some extent of platinum particles of Pt/C were covered by a insulation property cluster of Nafion; therefor, an efficient formation of the three-phase interface was not achieved. In the present study, polyelectrolyte complex(PEC) was used with Pt/C instead of Nafion. PEC, which has a small cluster size, could be expected not to cover the Pt particle. An electrode catalyst layer consisting of the Pt/C and a PEC was prepared on an Au flag electrode. The platinum utilization efficiency was measured by cyclic voltammetry. As a result, it was found that the Pt surface area of the Pt/C-PEC was 1.5-times larger than that of Pt/C-Nafion.

Keywords : polyelectrolyte complex; Pt/C; electrocatalyst layer; Nafion; polymer electrolyte fuel cell.

Spectrophotometric determination of aluminum in water using polymer liquid membrane pretreated with pyrocatechol violet

Tsuneaki Maeda¹, Miki Takizawa², Tatsuro Nakagama^1,2, Katsumi Uchiyama² and Toshiyuki Hobo²

(Received 11 May 2004, Accepted 20 July 2004)

Spectrophotometric measurement is a popular and easy technique for the determination of pollutants. In most cases, cumbersome enrichment procedures, using several toxic and environmentally harmful organic solvents, are required in the pretreatment step of the measurement. Recently, solid-phase micro extraction (SPME) using a liquid phase for gas chromatography (GC) has been used for the sample preparation of environmental pollutants in GC and liquid chromatography. In this study, a solvent-less extractive enrichment technique using a GC liquid phase was developed. The membrane of the liquid phase was prepared on a quartz plate, and the prepared plate was dipped into a chromophore aqueous solution for a given time. The plate was then dipped in aluminum aqueous solution. It was expected that aluminum ion could be extracted into the polymer liquid membrane and complexed with the chromophore. When a plate with a cationic silicone liquid membrane of 30 micro meters in thickness containing Pyrocatechol Violet (PV) was dipped in ca. 25 ml of an aluminum aqueous solution, the absorbance of the spot at the wavelength of the maximum absorbance of the aluminum gradually increased, and that of the PV gradually decreased. The detection limit of aluminum was 0.23 µg (3σ). This method was applied for ppb-level alminum determination using PV as a chromophore and a polymer liquid phase.

Keywords : environmental; extraction & enrichment technique; GC liquid phase; chromophore.

Laser ablation and low-pressure helium-ICP-MS for the analysis of alumina powder dispersed in glycerol

Taketoshi Nagayasu¹, Hideo Hayashi² and Masataka Hiraide¹

(Received 11 May 2004, Accepted 23 July 2004)

A combined method of laser ablation (LA) and ICP-MS has gained much attention as a direct analytical method for solid samples. The determination of some elements, however, is seriously disturbed by isobaric interferences, mainly caused by argon and ambient air constituents. The use of low-pressure helium-ICP is a promising solution of the problem. A 1:1 mixture of alumina powder and glycerol was deaerated and irradiated with a pulsed laser beam (150 mJ) for 10 s. The sample aerosol was transported to the ICP with a stream of helium. Indium was used as an internal standard for correcting the ablated sample amount. Calibration curves were prepared from glycerol containing high-purity alumina, trace metals and indium. The detection limits for Cr, Mn, Fe, Co, Ni, and Cu approached the fractional ppm levels. The proposed method was successfully applied to the analysis of different alumina samples (99~99.995% purity).

Keywords : low-pressure helium-ICP-MS; laser ablation; alumina powder; direct analysis.

Notes

Recovery of chromium(VI) in chromium plating solution by using the cationic surfactant-gel adsorption method

Keiichiro Yamamoto¹, Takayuki Nakai¹, Yoshiko Murakami¹, Yoshiaki Sasaki¹ and Shoji Tagashira¹

(Received 30 April 2004, Accepted 14 June 2004)

The separation and recovery of chromium(VI) by using a cationic surfactant were investigated. Chromium(VI) reacted with cetylpyridinium chloride (CPC) to form a (HCr₂O₇^-)(CP⁺) ion-pair under an acidic condition. This ion-pair was sparingly soluble in water, and was separated as a precipitate with CPC from aqueous solution by centrifugation. In order to desorb the chromium(VI) from CP⁺, the reduction of chromium(VI) to chromium(III) having positive charge was performed by using sodium sulfite in the presence of sulfuric acid. Finally, chromium was then recovered as Cr(OH)₃ under a basic condition. Optimization for the quantitative recovery of chromium(VI) was carried out. This method was applied to the recovery of chromium(VI) in chrome plating including Cr(III)+(VI), Fe, Zn, Cu, Al, Mn and Sb.

Keywords : chromium(VI); ion-pair; reduction with sulfite; surfactant-gel adsorption method.

Field investigation of PAHs in soils around Nara city

Ryuji Takeda¹, Yoshimasa Ikuma¹, Sadayoshi Matsumoto^1,2, Sadao Komemushi^1,2 and Akiyoshi Sawabe^1,2

(Received 6 May 2004, Accepted 17 June 2004)

PAHs are the general term of the compounds, having two or more benzene rings. These are discharged from diesel motor gas, tanker accidents, oil emissions by cars, and so on. They float in the atmosphere, and it is considered that they are absorbed in soil as a result of rain. Generally, compounds that have two or three benzene rings show only toxicity, whereas these having four or more benzene rings show toxicity, carcinogenicity and mutagenicity. Especially, benzo(a)pyrene was shown to be an agency of an endocrine disrupter. We investigated the action of 16 PAHs specified by the U.S. EPA in soil around Nara city. Soil was collected from different locations involving traffic and vegetation. Soil from three locations around our university were collected every month for investigating seasonal movement. PAHs were extracted from soil by soxhlet extraction with dichloromethane. They were then analyzed quantitatively by HPLC/UV. We classed PAHs by the number of rings, and examined the concentration and seasonal movements. All content of 16 PAHs in soils increased in proportion to traffic volume. At the same locations of traffic volume, the gravitation at a location with a plant with all 16 PAHs in soils was, furthermore, found to have a low concentration. There were different seasonal movements of the 2,3-ring and 4, 5, 6-ring PAHs. 4, 5, 6-ring PAHs have strong correlations each others(r>0.79), but there was no correlation between 2, 3-ring and 4, 5, 6-ring PAHs. As a result, the traffic volumes are exposition sources of 4, 5, 6-ring PAHs in soils.

Keywords : PAHs; soil; HPLC; endocrine disrupter.

Age determination of submarine hydrothermal barite deposits by the ²¹⁰Pb/²²⁶Ra method

Takuroh Noguchi¹, Hiroki Arasaki², Tamotsu Oomori² and Jitsuya Takada³

(Received 7 May 2004, Accepted 30 June 2004)

An age determination and the chemical composition of hydrothermal barite, collected from an Okinawa Trough hydrothermal field, were studied. Initially contaminated ²¹⁰Pb in sulfide and other minerals were leached by a chemical treatment. After the treatment, the radioactivity and chemical composition were determined by gamma spectrometry and neutron activation analysis, respectively. The following results were obtained: 1. An accurate and reproducible age was obtained by a chemical treatment of barite samples. 2. A matrix effect of barite samples on gamma-ray measurement was significantly observed, and was calibrated with mixed NaCl-BaSO₄ references. 3. The precipitation age, calculated by the ²¹⁰Pb/²²⁶Ra method after correction was concordant with the ²²⁸Th/²²⁸Ra and ²²⁸Ra/²²⁶Ra methods. 4. The Sr/Ba weight ratios were in the range of 0.007~0.053, which seems to have positive relationship with the temperature of the hydrothermal vent fluid. 5. A chronological study of barite in sample No. 974R1 showed that Sr/Ba weight ratio seems to be high in older samples, and tends to decrease in young samples, which would suggest a possible alteration of the hydrothermal activity in this field.

Keywords : barite; ²¹⁰Pb/²²⁶Ra method; Sr/Ba ratio; hydrothermal activity; Okinawa Trough; radioactivity.

Speciation analysis of chromium in environmental water samples from Niigata Prefecture by using ion-exchange/ICP-AES

Yuki Iwasaki¹, Naoki Kano², Kazuhiro Omori², Hiroshi Imaizumi² and Toshio Ishizuka³

(Received 7 May 2004, Accepted 7 July 2004)

A simple and an efficient preconcentration method for the separate determination of each species of chromium {i.e., Cr(III) and Cr(VI)} in environmental water samples has been investigated, followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES). This method is based on the following ion-exchange method. Cr(III) was adsorbed on cation-exchange resin, and Cr(VI) on anion-exchange resin. The retained Cr(III) and Cr(VI) were quantitatively eluted with 2 mol dm^-3 hydrochloric acid (HCl) and 2 mol dm^-3 potassium chloride (KCl), respectively. The preconcentration factor was 100 for Cr(III) and 300 for Cr(VI) in this work, and the detection limits were 0.03 µg dm^-3 in Cr(III) and 0.01 µg dm^-3 in Cr(VI). The method has been applied to environmental water samples from Niigata Prefecture. The recoveries of Cr(III) and Cr(VI) in environmental water samples were all 94~98%, and the effect of interference from the coexistence ion was not detected. Therefore, the above-mentioned method is applicable to environmental water samples.

Keywords : speciation; chromium; environmental waters; Niigata Prefecture; ion-exchange/ICP-AES.

Cyclic flow-injection analysis for Fe(II)-1,10-phenanthroline using polyurethane foam

Kazuyoshi Minamisawa¹, Takashi Yokoyama¹ and Michio Zenki¹

(Received 10 May 2004, Accepted 7 July 2004)

The spectrophotometric determination of Fe(II) with 1,10-phenanthroline (phen) was carried out by a cyclic flow-injection analysis. Tandem glass columns (4 mm i.d., 8 cm long, each) packed with polyurethane foam (PUF, weight; 0.16 g×2) for the removal of Fe(II)-(phen)₃ complex were incorporated in the system, allowing a repetitive determination of Fe(II). A solution of 2.0×10^-3 M phen and 5.0×10^-4 M sodium dodecyl sulfate (SDS) in a 0.1 M acetate buffer (pH 4.7) in a single reservoir (50 ml) was continuously circulated at a constant flow rate of 1.5 ml min^-1. Into the stream, an aliquot (5 µl) of a sample containing Fe(II) was injected by means of a 6-way valve. The formed complex was monitored spectophotometrically at 510 nm. The stream was passed through glass columns, which were introduced after the flow-through cell, and then returned to the reservoir. The colored Fe(II)-(phen)₃-SDS ion associates were adsorbed onto PUF, which allowed a baseline constant, and made it possible to adopt a cyclic FIA. This method allowed as many as 100 repetitive determinations of 6 ppm Fe(II) solutions with the same 50 ml of the circulating solution.

Keywords : cyclic FIA; 1,10-phenanthroline; repetitive determination of iron; polyurethane foam.

Simple determination of lipase-catalyzed cleavage products of triacylglycerol by gas chromatography

Chidsuru Satou¹, Mariko Kobayashi¹, Ai Takeda¹, Taeko Ito², Kenji Shimada¹ and Susumu Yamato¹

(Received 10 May 2004, Accepted 13 July 2004)

A convenient analytical method using high-temperature gas chromatography for the determination of mono- and diacylglycerols, lipase-catalyzed cleavage products of triacylglycerol (TG), has been developed. In this study, analytical conditions were examined using triolein (TO), diolein (DO) and monoolein (MO) as standard materials. As a result, a trimethylsilyl(TMS) derivatization with N,O-bis(trimethylsilyl)acetamide and a well-programmed column temperature using a low polar capillary column permitted the regiospecific analysis of 1-MO, 2-MO, 1,2-DO and 1,3-DO. Solid-phase extraction using an aminopropyl silica cartridge was effective for the sequential treatment of lipase-catalyzed cleavage products of TO. A quantitative analysis became feasible by the use of tricaprin as an internal standard. It was suggested that the present method was useful for the analysis of a different manner of cleavage due to the different kinds of TGs and lipases.

Keywords : gas chromatography; mono- and diacylglycerol; triacylglycerol; lipase; triolein.

Spectrophotometric determination of nonionic surfactants with iron(III)-thiocyanate by using a PTFE membrane filter

Sosuke Matsueda¹ and Eiko Nakamura²

(Received 31 May 2004, Accepted 15 July 2004)

We reported on a spectrophotometric method for the determination of polyoxyethylene nonionic surfactants(NS) using a polytetrafluoroethylene(PTFE) membrane filter in a previous paper. The method is based on the collection of NS on the filter, and the formation of an NS- iron(III)-thiocyanate complex. Although it is a simple and rapid method, it is not good regarding the precision of repeated blank tests, because of the instability of a mixed solution of potassium thiocyanate and iron(III) chloride. In the present work, the concentration of the potassium thiocyanate and iron(III) chloride solution was studied in detail to improve the precision of repeated blank tests. The improved procedure was as follows. After a 100 ml sample solution(0~120 µg heptaoxyethylenedodecylether) was filtered through a PTFE filter (pore size: 0.1 µm, Φ: 25 mm), 2 ml of a potassium thiocyanate solution(6 M) and 2 ml of an iron(III) chloride solution(8 mM) were added on the filter, respectively. NS associated with iron(III)-thiocyanate was eluted with 5 ml of methanol, and the absorbance of the solution was measured at 510 nm. The precision of repeated tests (n=3) was ca. 2% on both the blank and the sample.

Keywords : polyoxyethylene nonionic surfactants; PTFE membrane filter; iron(III)-thiocyanate complex.

Performance of germanium(IV) complexes as anionophore

Hiroshige Uno¹, Takashi Suzuki¹, Yasumasa Goto¹, Shinsuke Itoh¹, Takashi Yasui¹ and Akio Yuchi¹

(Received 7 May 2004, Accepted 20 July 2004)

A few germanium(IV) complexes were prepared and examined for the anionophore. A nitrilotriphenolato complex ([Ge₂(ntp)₂O]) with three coordinating phenolates around Ge(IV) showed a sub-Nernstian response (40 mV/decade) to fluoride in the range of 10^-3~10^-1 mol dm^-3 as a carrier of ion-selective electrodes(ISEs). The dynamic range was extended to 10^-4~10^-1 mol dm^-3 in the presence of cationic additives. Spectroscopic studies on the reaction of this complex with anions in dimethyl sulfoxide demonstrated the reaction stoichiometry of Ge(IV):A^-=1:1 and the thermodynamic stability order of F^->CH₃COO^->H₂PO₄^-. The reaction selectivity agreed with that of potentiometry with ISEs. A bis(catecholato) complex with four phenolates showed no response to anions, and a bis(aminophenolato) complex with two phenolates was not stable enough in the reaction with anions.

Keywords : ion-selective electrode; germanium(IV) complex; ionophore; anion.

Synthesis of iminodi(methylphosphonic acid)-type chitosan resin and its adsorption behavior for trace metals

Satoko Yamakawa¹, Koji Oshita¹, Akhmad Sabarudin¹, Mitsuko Oshima¹ and Shoji Motomizu¹

(Received 7 May 2004, Accepted 20 July 2004)

A chitosan-based resin possessing the iminodi(methylphosphonic acid) moiety (IDP-type chitosan resin) was synthesized by using cross-linked chitosan as a base material. The adsorption behavior of trace metal ions on the IDP-type chitosan resin was systematically investigated using a mini-column (1 ml of the resin) packed with the resin. The concentrations of metal ions in the effluents were measured by ICP-MS and ICP-AES. The resin could adsorb four metals, such as In(III), Sn(II), Th(IV), and U(VI), by almost 100% over a wide pH range (1~7). Uranium(VI) and thorium could not be eluted with nitric acid and hydrochloric acid (1~6 M); other metal ions were easily and readily eluted with 1 M nitric acid. The IDP-type chitosan resin synthesized in this work can be applied to the separation of U(VI) and Th(IV) from other metal ions.

Keywords : chitosan resin; iminodi(methylphosphonic acid (IDP); uranium(VI); thorium(IV); heavy metals.

Analytical Reports

Interference from chlorine and its elimination on the determination of total phosphorus in sea water by the peroxodisulfate digestion/molybdenum blue method

Shingo Fujita¹ and Eiko Nakamura²

(Received 31 May 2004, Accepted 16 July 2004)

Interference with chlorine on the formation of molybdenum blue was studied to determine the total phosphorus in sea water. When a sample containing chloride ion was digested with peroxodisulfate, chlorine was produced. The molybdenum blue formed in the absence of chlorine had absorption maxima at 880 and 710 nm, and the molar absorptivity at 710 nm was less than that at 880 nm. However, one of the absorption maxima of the molybdenum blue formed in the presence of chlorine shifted from 710 nm to 730 nm, and its molar absorptivity was larger than at 880 nm. The interference could be eliminated by boiling the digested sample and increasing the concentration of ascorbic acid in a mixed-reagent solution prepared by mixing acidic molybdate with ascorbic acid, but could not be eliminated by the addition of a sodium hydrogen sulfite solution.

Keywords : phosphomolybdenum blue; interference of chlorine on molybdenum blue method; digestion with peroxodisulfate.

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