The surface of gel-type anion exchange resin was modified by the adsorption of an anionic polyelectrorite: polycondensation product of sodium naphthalene sulfonate and formaldehyde (trade name, Demol N). After the adsorption of the polymer, ion exchange capacity decreased and the rate of ion exchange reaction became slow though ion exchange equilibrium constants between two anions did not changed. Especially, the ion exchange rate of divalent anions was slower than that of the monovalent anions. Because an anionic polyelectrorite layer was formed on the resin particle, the ion exchange of anions with anion exchange site was retarded by sieving effect with the layer and the divalent anions were difficult to ion exchange compared with the monovalent anion due to existence of the opposite charged layer to ion exchange groups. Using the modified anion exchange resin in the hydroxide ion form, separation of nitrate ion from sulfate ion was attempted. The modified resin was immersed in the mixture solution of nitrate and sulfate ions, and the solution was shaken for definite time. The nitrate ion was preferentially adsorbed on the resin. The resin was separated and introduced in the potassium perchlorate solution. After shaking for 90minutes, the nitrate ion in the solution was determined by use of ion-chromatography. The separation and enrichment of nitrate ion from 50-fold amount of sulfate ions was accomplished.

View full abstract

A native and two types of methylated β-cyclodextrin(CD)-bonded stationary phases have been prepared and their ability to separate enantiomers of eight 2, 4-dinitrophenyl amino acids was investigated by revered-phase high performance liquid chromatography. When heptakis(3-O-methyl)-β-CD bonded stationary phase was compared with the native β-CD stationary phase, increased enantioselectivity and peak resolution were observed for aromatic amino acids. Effects of organic modifier content and pH of the mobile phase on retention and enantioselectivity for the analytes were examined to optimize mobile phase conditions. The elution order of racemates of all analytes on both the native and heptakis(3-O-methyl)-β-CD bonded stationary phases was D before L enantiomer. The structural features of the analytes on retention, enantioselectivity and peak resolution were examined and discussed

View full abstract

Branched-saccharide-chitosan resins and beads selectively adsorbed germanium(IV) from aqueous solutions containing semimetals over the range of weakly acidic to basic media by a batch method. The chitosan derivatives had large adsorption capacities of up to about 2mmol g^-1. On the other hand, by a column method, the chitosan derivatives adsorbed both germanium(IV) and boron. However, when a mixture of germanium(IV) and boron was applied to the column, boron, initially adsorbed on the column, was gradually substituted by germanium(IV), and was finally eluted. The germanium(IV), adsorbed on the column, was almost quantitatively recovered by elution with hydrochloric acid.

View full abstract

Octadecyl substituted β-cyclodextrin, which was synthesized in DMSO, was dynamically coated on octadecylsilanized (ODS) silica through hydrophobic interaction. This type of immobilization is readily feasible, not being accompanied by any chemical reactions. The dynamically coated β-cyclodextrin stationary phase was used for liquid chromatographic separation of the geometrical isomers of substituted phenols. The chromatographic property of the coated β-cyclodextrin column was different from that of the ODS column. Its separation efficiency for the phenols was greater than that of the ODS column.

View full abstract

Characteristics of a column with continuously varying properties were investigated. The velocity change was induced by column′s geometry, with a continuously varying diameter inside the column. This column was compared to a standard analytical column and to a narrower classical column in view of separation of acyclovir from the human plasma samples. Typical performance of all columns operating under the same conditions was examined. The proposed column configuration reduces retention times compared to widely used analytical columns. Compared to the standard column, a higher linear velocity at the same flow-rate was achieved. Therefore, the retention times are shorter andthe consumption of the mobile phase was smaller.

View full abstract

The polynuclear aromatic hydrocarbons(PAHs) were separated by capillary electrophoresis with uncoated fused silica capillary(50μm i.d., total length 50cm, effective length 32cm). A borate buffer solution containing sodium dodecyl sulfate, β-cyclodextrin, and acetonitrile was utilized. The separation was monitored by a spectrophotometer at the wavelength of 220nm. The detection limits of some PAHs were in the range of 0.1-2μg/mL. It is satisfactory to apply this method to the analysis of some PAHs in environmental samples.

View full abstract

Ion association reactions between monovalent- and divalent- aromatic anions and their pairing ions, quaternary ammonium ions, in an aqueous solution were analyzed by using electrophoretic mobility of aromatic anions (analyte anions). The electrophoretic mobility of analyte anions decreased with increasing the concentrations of quaternary ammonium ions added in the migrating buffer solutions. The electrophoretic mobility of the analyte anions was obtained by using capillary zone electrophoresis. The change in electrophoretic mobility was analyzed to obtain ion association constants (K_ass) by a non-linear least-squares analysis method, as well as some other linear least-squares analysis methods. The larger the decreases in the mobility of the analyte anions with increasing the amounts of pairing ions, the larger the K_ass values were. Ion association constants obtained were larger in divalent anions than in monovalent anions, which suggested the contribution of electrostatic interactions to ion associability in the aqueous solution. The K_ass values became larger in the anions possessing naphthalene ring than in those possessing benzene ring, and also became larger in the bulkier pairing cations than in less bulky cations. These results indicate that the hydrophobicity of the ions will contribute to the ion associability positively. In comparison of ion associability of position isomers with each other, the ion associablity of β-substituted naphthalene isomers were larger than those of α-substituted ones, which agreed with the acid dissociation property of the anions; that is, the more basic the position isomer is, the more associable the isomer is. Differences in K_ass values among functional groups, such as -O^-, -CO₂^-, and -SO₃^-, were small, compared with the differences in liquid- liquid extraction constants (K_ex) of ion associates.

View full abstract

Determination of inorganic anions by capillary zone electrophoresis is reported in this study. An anions mixture of bromide, chloride, fluoride, nitrite, sulfite, sulfate, perchlorate, chlorate and chlorite was separated by a capillary column and detected by indirect UV method. The running buffer contained 5mM ammonium dichromate, 10mM ammonium acetate, 20mM diethylenetriamine, and in 10% methanol solution at pH 9.3. A potential of 15kV at the cathode(reversed polarity) was utilized for the separation of inorganic anions. A complete separation of anions was achieved in less than 10min and the applicabilities of the method were demonstrated for forensic evidences. We performed analysis of inorganic anions in toluene inhaled human′s urine and in postmortem bloods by capillary zone electrophoresis and ion chromatography

View full abstract

A study on the separation and detection of organic and inorganic phosphorus compounds using a capillary electrophoresis (CE) system has been performed. The separation of 18 phosphorus compounds is characterized by good resolution and analysis times less than 20min using EDTA (ethylenediaminetetraacetic acid) electrolyte. The cumulative data demonstrate that it is possible to undertake simultaneously separation of both UV-absorbing and UV-transparent components with EDTA electrolyte. UV-absorbing components were measured at 210nm and UV transparent components indirectly determined at 210nm. The influence of electrolyte (EDTA) concentration, operating buffer pH, separation voltage, temperature, and electroosmotic flow modifier (OFM anion-BT) concentration is described. The optimum CE system has operating parameters of 5mM EDTA, pH 10.3, 20kV of separation voltage, 25°C, 0.15mM OFM anion-BT, 70cm×75μm i.d. fused silica capillary, and UV photometry detection at 210nm.

View full abstract

Polyacrylamide gel electrophoresis (PAGE) is a widely used method for separating and analyzing chlorophyll/carotenoid binding-proteins. However, extraction of pigments from the proteins in the gel using organic solvents is inefficient. We modified the gel composition by adding various hydrophilic water-soluble polymers to the acrylamide before polymerization. The inclusion of 3% dextran T500 produced a gel with much more elasticity and greatly improved both the speed and efficiency of pigment extraction. In 30min, extraction of pigments was completed whether in 80% acetone or in 95% N, N-dimethylformamide. More than 90% of the chlorophyll and carotenoid applied to the ge was recovered by solvent extraction. The current method is advantageous for separation and quantitative analysis of pigments associated with proteins.

View full abstract

The pyrolysic behaviors of coumarone-indene resin and alkylphenol resorcinol-formaldehyde resin have been studied for the direct component analysis in cured rubber. The pyrolysis-pathways based upon main primary degradation products have been proposed to identify the mass spectrum of pyrolyzates. From the coumarone-indene resin, the indene, coumarone, coumarone-indene (m/z 234), and indene-indene (m/z 232) were observed as the characteristic monomeric and/or sequential pyrolyzates. Resorcinol and t-octylphenol were observed as main pyrolyzates in alkylphenol resorcinol-formaldehyde. Upon these pyrolysic behavior, it would be readily available to identify these oligomeric resins in a cured rubber.

View full abstract

Four heptakis(6-O-alkyldimethylsilyl-2, 3-di-O-ethyl)-β-cyclodextrin (CD) having 6-O-alkyl groups of different chain length, heptakis(6-O-trimethylsilyl-2, 3-di-O-ethyl)-β-CD (MTDE-β-CD), heptakis(6-O-ethyldimethylsilyl-2, 3-di-O-ethyl)-β-CD (ETDE-β-CD), heptakis(6-O-octyldimethylsilyl-2, 3-di-O-ethyl)-β-CD (OTDE-β-CD) and heptakis(6-O-octadecyldimethylsilyl-2, 3-di-O-ethyl)-β-CD (ODDE-β-CD), were prepared and effect of the chain length of the 6-O-alkyl moiety on the enantioselectivity of the CD derivatives as chiral stationary phases were compared by measuring separation factors of a range of chiral test compounds in capillary gas chromatography. Enantioselectivity of the CD derivatives was observed to be in the order, ETDE-β-CD_??_MTDE-β-CD>OTDE-β-CD>ODDE-β-CD.

View full abstract

A fast, automated, and sensitive method has been developed for the determination of ammonia gas in the atmosphere. The method involves diffusion scrubber based sampling followed by ion chromatographic analysis with conductivity detection. To ensure maximum sensitivity, specially purified eluent was used. The method has 0.02ppbv(2 sigma) LOD. Single measurement can be made in less than 5 minutes. The method has been successfully applied to Seoul air monitoring.

View full abstract

Electrochemical activity and stability of pure lead dioxide(PbO₂) and lead dioxide incorporated with metal ions (As⁵⁺, Bi³⁺, Cr³⁺, Fe³⁺ and Ni²⁺) were studied. Heterogeneous rate constants for oxidation of numerous inorganic and organic compounds at PbO₂ were compared with those at mixed lead dioxide electrodes. Among the tested metal ions, it turns out that arsenic is one of the promising elements. The electrochemical stability of the mixed oxide electrode prepared in an optimum condition, i.e., As⁵⁺/Pb²⁺ in the deposition solution, was increased compared to that of PbO₂. For the application of the electrode material to electroanalysis, detection of thiourea, for example, at PbO₂, and As incorporated lead dioxide electrodes(As/PbO₂) as working electrodes in a thin layer electrochemical cell for flow injection analysis(FIA) was investigated by a constant-potential amperometry. Sensitive detection of thiourea with a detection limit of 1.4x10^-7M was achieved with PbO₂ and As/PbO₂ electrodes.

View full abstract

In the medium of dilute sulfuric acid germanium(IV)-trihydroxybenzoic acid complex produced an adsorptive current at-0.62V(vs. SCE), which could produce a parallel catalytic current in the presence of vanadium(IV). After adding EDTA, this current could be further increased.The sensitivity was raised to about 1200-times higher than that in the absence of vanadium(IV) and EDTA in above-mentioned medium. The chemical reaction rate constant(k₁) was calculated to be 14.4×10⁶L/mol s^-1. The peak height(second derivative)(i_p") was proportional to the concentration of germanium(IV)(C_Ge(IV)) in the range of 0.04-20μg/L Ge(IV). The correlation coefficient (r) and detection limit (DL) were 0.9996 and 5×10^-11mol/L Ge(IV) respectively. The composition of complex, the apparent stability constant (k) of this complex, the current property, the mechanism of the electrode reaction and the mechanism of the electrochemical response enhanced by EDTA were investigated in detail. Possible interferences were evaluated. The proposed method was applied to determine the trace germanium in alloys with satisfactory results.

View full abstract

Theory of the voltammetric or polarographic ion transfer current of organic amines at the water/organic solvent interface is discussed. Theoretical equations of the current vs. potential curves are derived on the basis of the reaction layer theory. The theoretical predictions are in good agreement with experimental results obtained with procaine and 4-ethylaniline at nitrobenzene/water interface using a dropping electrolyte electrode. Ion-transfer voltammetry and polarography is useful for study of the partition of amines between water and an organic solvent phase in both neutral and protonated forms and of the protonation reaction in water phase as well.

View full abstract

Sodium-selective membranes based on room temperature vulcanizing-type silicone rubber (RTV-type SR) matrix and tert-butyl calix[4]arene-tetraacetic acid tetraethyl ester (1.0wt %) have been developed for all-solid-state-type electrodes. It was observed that the potentiometric response, stability and lifetime of these SR membrane-based all-solid-state electrodes critically depend on the type of lipophilic salts employed. Among the several phenyl borate derivative-based additives examined, the SR membranes prepared with 0.5wt % tetrakis[3, 5-bis(trifluoromethyl)phenyl]borate salt (TFPB) exhibited low impedance, resulting in electrochemical performance comparable to that of the PVC-based membranes mounted in conventional electrodes. The lifetime of all-solid-state electrodes with SR/TPFB/tert-butyl calix[4]arene tetraethyl ester was longer than 230 days.

View full abstract

This study is concerned with improvement of the response time of the amperometric oxygen sensors of the type, Ag_??_Ag₆I₄WO₄_??_PbSnF₄_??_sensing electrode, O₂, of which sensing electrode was a mixture of iron(II)phthalocyanine, PbSnF₄ and a whisker material (one of 9Al₂O₃•2B₂O₃ and TiO₂ whiskers different in length, aspect ratio and conductivity). A good linear relation was found between the short-circuit-current and the square root of oxygen partial pressure for all the sensing electrode mixtures. The response time was strongly influenced by the length and conductivity of the incorporated whisker materials. Incorporation of an whisker material with appropriate length (-20μm), conductivity (-10-1S cm-1) and aspect ratio (20) was found to allow fast response (20s) at room temperature. The fast response results from formation of uniform reduction sites on the conductive whisker network in the sensing electrode.

View full abstract

Ion-transfer voltammetry of the facilitated transfer of Pb²⁺ ion by 1, 4, 7, 10, 13, 16-hexathiacyclooctadecane across the polarizable nitrobenzene/water interface has been applied to the study of complexes of Pb²⁺ ion with hydrophilic ligands, acetate^-, tartarate^2-, and citrate^3- ions in aqueous media. The formal formation constants of 1:1, 1:2, and 1:3 Pb²⁺-acetate^- complexes were determined to be 10^2.3M^-1, 10^3.0M^-2, and 10^4.0M^-3. The dissociation and association rate constants were determined to be 2.1×10³s^-1and 2.2×10⁷ M^-1 s^-1 for 1:1 Pb²⁺ -tartarate^2- complex and 4.5×10⁴s^-1 and 8.O×10¹⁰M^-1 s^-1 for 1:1 Pb²⁺ -citrate^3- complex, respectively.

View full abstract

Solid-state oxygen sensors based on two superionic conductors, of the type, Ag_??_Ag₆I₄WO₄_??_PbSnF₄-Ca(OH)₂_??_ sensing electrode, O₂, sensing electrode: a mixture of a carbon material, iron(II) phthalocyanine (FePc) and PbSnF₄ were constructed The hydroxide Ca(OH)₂ was incorporated in PbSnF₄ at different compositions of 0-23 mass% to suppress humidity interference with the response of the short circuit current. Similar linear relations were found between the short circuit current and the square root of oxygen partial pressure regardless of incorporation of Ca(OH)₂. On the other hand, the incorporation suppressed an increase in short circuit current caused by humidity, without undesirable effects on response time and sensitivity. The optimized content of Ca(OH)₂ was in a range of 13-15 mass%. The mechanism of the suppression was also discussed.

View full abstract

Detection of DNA is a very important task for molecular biology and biomedical field. We have investigated electrochemical behavior of double-stranded DNA and single-stranded DNA adsorbed on conducting polymer modified electrode in presence of cobalt complex. The possibility of using such electrode as gene detector is discussed.

View full abstract

Cyclic voltammograms and electrochemical impedance spectra of zinc electrodes in deaerated dilute KOH solutions have been studied. Under cathodic polarization from the equilibrium potential, cathodic current of hydrogen evolution is larger than the anodic current of zinc oxidation. The potential starting the anodic dissolution of zinc is about the same as in concentrated solutions. The passivation films start to be formed at the anodic dissolution potentials. Under anodic polarizations, the zinc electrode surfaces are partially coverd with the precipitated Zn(OH)₂ and/or ZnO, where composition can be expressed as Zn_yO_x(OH)_2-2x with y_??_1 and 0_??_x_??_1. Thus, the passive film composition is dependant on the anodic potential applied. The resultant cathodic stripping peak potentials shift towards cathodic direction with more anodic polarization. Electrochemical impedance spectra have also been analyzed to characterize the interface.

View full abstract

This paper describes the response characteristics of membrane-covered oxygen sensors using 0.1M tetramethylammonium perchlorate-propylene carbonate (TMAP-PC) electrolyte and highly viscous TMAP-PC-SiO₂ electrolytes containing an inorganic gelling agent of ultrafine SiO₂. The polarographic sensors consisted of a poly(tetrafluoroethylene) film, a gold-plated working electrode, 4cm³ of electrolyte, a Sn counter electrode and a Ag quasi-reference electrode. With the working electrode controlled at -1.1V vs. the Ag electrode, a similar linear relation with a sensitivity of 34-42 μA was found between the diffusion-controlled limiting current and oxygen partial pressure for all the PC-based electrolytes. The gelled electrolyte have the merit that there is no fear of CO₂ interference, leakage, and deposition of the cell-reaction product on the working electrode.

View full abstract

Oxidation of epinephrine at a gold electrode was studied in acidic solutions by a near normal incidence reflectance spectroelectrochemical (NNIRS) system. Also, cyclic voltammetric(CV) data were used to interpret the oxidation pathway of epinephrine. Some spectroscopic results are in good agreement with the previous reports at a carbon paste electrode. However, assignment of each peak in the CVs is not always in good agreement with the past findings, especially the formation of dehydrated form of leucoadrenochrome is not likely to occur under acidic conditions

View full abstract

Bis(15-crown-5 ether) derivatized from a xanthene-4, 5-dicarboxylic acid skeleton was studied as an ionophore for a new K⁺-selective electrode. The polymeric liquid membrane based on this ionophore exhibits Nernstian behavior and optimization of experimental conditions for potentiometric analysis offers a wide linear dynamic range, reasonable detection limit, good durability and hysteresis within a limited error. Due to the well-preorganized structure, the selectivity over Na⁺ is comparable to those of commercialized K⁺-selective ionophores and the interferences by some cations such as Rb⁺ and Cs⁺ are reduced. Except slightly slow response, the enhanced recognition ability is reminiscent of the natural antibiotic valinomycin.

View full abstract

Multimolecular layers of 2, 2, 6, 6-tetramethyl-1-piperidinyloxy(TEMPO) was immobilized on a glassy carbon electrode coated with polyacrylic acid. The coverage of TEMPO was about 2x 10^-7mol/cm² and E^o′_surf was 0.36V vs. a Ag/Ag⁺(0.10M) reference electrode. Electrocatalytic oxidation of benzyl alcohol with a TEMPO-modified electrode was observed by cyclic and differential pulse voltammetries. Electrocatalytic current measured by amperometry at an applied potential of 0.45V was linearly increased as the concentration of benzyl alcohol was increased.

View full abstract

The substrate selectivity of the known Ru(bpy)₃²⁺ eleetrochemiluminescence (ECL) is changed by coating a Pt working electrode with a Ru(bpy)₃²⁺-modified chitosan membrane and successively with a silica gel membrane that was prepared by the sol-gel method using tetramethoxysilane as a precursor. The double coating resulted in a high selectivity toward oxalic acid at pH 6.8, lowering relative ECL responses to trimethylamine, proline and 4-hydrox.yproline about 2.8, 3.4 and 3.8 times, respectively, compared to those obtained with a Pt electrode coated singly with the modified chitosan.

View full abstract

A method for the measurement of toluene, m, p, o-xylene, styrene and iso, n-butylacetate in workplace air of surface coating industries was developed. The target compounds were adsorbed on Tenax-TA sampling tubes then thermally desorbed via a homemade split device prior to cryotrapping and analyzed by gas chromatograph with flame ionization detector. All the compounds including the m, p-xylene isomer can be separated completely by a DB-WAX capillary column. Breakthrough volumes of target compounds were measured by photoionization detector under the condition of 30±3°C and 80±5% relative humidity in a concentration level of the twice threshold limit value. Results showed the breakthrough volumes were concentration dependent and influenced by the competitive effect between different compounds. The thermal desorption recovery yield of this method was in the range of 94.8%-101.2%. All the compounds can be stored safely within 15 days both in the room and freezing temperature. The developed method was compared well with the current method (charcoal adsorption and solvent extraction) in a real air monitoring at the same sampling place and time. The analyte concentrations are well below the prescribed limits in the test surface coating industry.

View full abstract

Poly(methyl methacrylate) (PMMA) thin films incorporating amphiphilic dyes, ruthenium tris(2, 2- bipyridine)-type complexes, were prepared by water casting. Films fabricated in this manner are peculiar with their well lined-up molecular orientations at the surface and thus are highly nonlinear effective. Unfortunately, like most other nonlinear materials, the surface orders of the dye molecules tend to collapse once exposed to heat. This work presents our recent studies on heat-induced molecular reorientation by probing SHG and fluorescence spectra. It shows that, in the course of heating between 20°C and 80°C, the secondary glass transition of PMMA molecules is responsible for both the randomization of the surface alignments of the Ru complex molecules and the migration of these molecules into the body of the PMMA layer.

View full abstract

A correlative study between the physical properties and the adsorptiveldesorptive properties of four activated carbons (RGI, RB-T, ROW and CG) for solid phase extraction (SPE) of phenols was carried out. In determining the adsorptive properties, a few differences were found between the distribution coefficients (K_D) and breakthrough volumes, which were attributed to the different physico-chemical properties of activated carbons. For phenol and chlorophenols, methylene chloride was the best desorbing solvent, but for other phenols, acetonitrile was the best solvent on an average.

View full abstract

Characteristics of the enhancement of the infrared transmission spectrum with the use of a thin Pb film were investigated from a point of view of its applications to a method for microanalyses. Magnitudes of the enhancements were kept constant at about maximum in a wide region of the Pb film thickness, which suggests that reproducible data are easily obtained without a strict control of the Pb film thickness. The calibration curve was linear over the quantity region between 50 and 500ng/cm².

View full abstract

X-ray photoelectron spectroscopy (XPS) was used to characterize the copper ion of 1, 10-phenanthroline (phen) complexes in the interlayer space of natural montmorillonite and artificial saponite. [Cu(phen)₂]²⁺ and [Cu(phen)₃]²⁺ were intercalated into the minerals instead of ion-exchangeable cations occupying the original interlayer space. Loading amount of complex can be varied up to 170% of cation exchange capacity (CEC) of each clay minerals. Cu(II) 2p photopeakes of [Cu(phen)₂]²⁺ and [Cu(phen)₃]²⁺ in saponite remarkably decrease as loading amount decreases from 170 to 50%, while Cu(I) photopeaks increase by photoreduction. X-ray diffraction (XRD) indicated that there was sufficient space to exist [Cu(phen)₂]²⁺ without any distortion at 170%. In montmorillonite, there is sufficient space even at 50% of CEC for [Cu(phen)₃]²⁺ and [Cu(phen)₂]²⁺. XPS spectra suggest two or more binding state of the complexes at Interlayer space of montmorillonite.

View full abstract

Adsorption of Pb(II), Cu(II) and Zn(II) on crosslinked or amidated pectic acid and alginic acid were examined. Adsorption experiments were carried out by the conventinal batch-method at 30°C from aqueous buffer solutions consisting of 0.1moldm^-3 HNO₃ and 0.1moldm^-3 HEPES. The order of adsorption was found to be as follows for all adsorbents; Pb(II)>Cu(II)>Zn(II). It was found that separation property of alginic acid amide for Pb(II) away from Cu(II) and Zn(II) was the most excellent among 4 adsorbent tested. Nearly complete separation can be achieved for Pb(II) away from Zn(II) at pH less than 3.9 with alginic acid amide.

View full abstract

Leaching experiments on a simulated borosilicate waste glass were performed using a static method in the presence of PbO and bentonite. Ions in leachates were analyzed by ICP, while leached samples were characterized by several surface analytical methods such as XPS, SEM, EPMA, XRD and topography. As the simulated waste glass was leached in the presence of PbO and bentomte, lead hydroxide and insoluble elements (Ti, Nd, Ru and Zr ) were detected on the surface, respectively. On the other hand, a large amount of uranyl hydroxide was found on the surface of it when the borosilicate glass with 25% U₃O₈ was leached in a soxhlet apparatus.

View full abstract

A new ERDA system using time of flight (TOF) detection was set up to realize both higher mass resolution and lower detection limit in RIEKN. The TOF spectrometer using a charged-particle detector and a time detector, and the data-acquisition system comprising CAMAC modules and a personal computer were installed. The mass resolution and the depth resolution of the system for a Si wafer have been determined using ²⁰Ne, ⁴⁰Ar and ¹³⁶Xe ions as probes. The incident energies were 20.0MeV for Ne, 41.5MeV and 22.6MeV for Ar and 138.1MeV for Xe, respectively. The mass resolutions of Si were found to be from 1.90 for 41.5MeV Ar to 3.32 for 22.6MeV Ar. Also, the depth resolutions were determined from 1.67×10¹⁷ atoms/cm² for 20.0MeV Ne to 2.67×10¹⁷ atoms/cm² for 138.1MeV Xe near to the sample surface. A PIQ film and a superconductor sample, Yba₂Cu₃O_7-x, were measured using Ar accelerated to 41.5MeV. H, C, N and O in the PIQ film and Y, Ba, Cu and O in the superconductor sample could be measured simultaneously and were clearly separated.

View full abstract

A chemical imaging method has been developed and applied for analysis of polycyclic aromatic hydrocarbons (PAH) in aerosols. It is based on fast collection of aerosol particles on non-fluorescing filters, followed by microscopic imaging of the induced fluorescence due to aerosol contamination. The proposed imaging technique provides full fluorescence spectrum at each pixel of the inspected object. It is based on imaging the interferograms produced by a Sagnac interferometer onto a cooled CCD camera in such a way that Fourier transform can be performed later at each pixel of the image. Application of classification algorithms enables simultaneous analysis of several PAH contaminants on the filter. Detection limits are as low as 10 fg.

View full abstract

Practical clean analytical methods for the monitoring of Ba, Mn, Cu and Ni in estuarine waters with salinity ranging from near zero to about 32‰ are reported. Three longitudinal surveys were conducted on the levels of Ba, Mn, Cu and Ni for Selangor River and Klang River from the upper estuary freshwater points to the river mouth. In addition, monitoring of dissolved Ba were carried out at a fixed estuarine station of the Selangor River over the daily flood-ebb tidal cycles for a neap tide and two spring tide occassions. The longitudinal surveys show both input and removal of the trace metals monitored during estuarine mixing. The fixed station study shows that the concentrations of dissolved Ba vary in the range from 3.4 to 5.7μg/L for neap tide samples, whereas concentrations ranging from 6 to 120μg/L were observed for spring tide samples. Variations of the trace metal concentrations over the daily tidal cycles and sample standing were dependent on the water salinity, pH, dissolved oxygen and suspended solids levels.

View full abstract

The applicability of a newly developed method, Graphite Furnace-Capacitively Coupled Plasma-Atomic Emission Spectrometry (GF-CCP-AES) for ppb level determination of hydride-forming metallic elements and heavy metals in drinking water was investigated. The intensity of the plasma background emission was found to be dependent on the graphite furnace temperature with emission lines limiting the choice of analytical lines for given analysis. Optimized analytical conditions are given below the concentration limits levels of health significance as specified by the Guidelines for Drinking Water given by the World Health Organization (WHO). A simple multi-element detection using a 1-meter spectrometer with photographic film detection was used and shown to provide sufficient sensitivity for rapid screening of analytical parameters specified in the WHO guidelines.

View full abstract

The thermal behaviors of potassium perchlorate with graphite powder were investigated by DTA, and the kinetic parameters of the thermal decomposition of potassium perchlorate with graphite powder were studied by dynamic TG. Graphite powder plays a catalytic role in thermal decomposition of potassium perchlorate. Adding graphite powder into potassium perchlorate results in remarkable acceleration effect on the decomposition of KClO₄.

View full abstract

Protonation equilibria of monomeric acid mixtures and of polyelectrolytes such as polyacrylic acid and fulvic acid have been studied by potentiometry. The observed degree of dissociation (α) as a function of pH obeys a simple integral equation assuming an unknown distribution of various ′intrinsic′ pK sites (f) and a global electrostatic effect for polymers (ΔpK). The latter can be estimated from the cylindrical Poisson-Boltzmann theory. The equation has the familiar form of convolution of signal (f) and response (α_site) functions, and can be solved by standard techniques of spectrum analysis. The resulting pK histogram f(pK) is useful for characterization of acid mixtures and environmental polyelectrolytes. Linear-programming (simplex) algorithm is shown to give a fairly discrete, delta-function-like histogram that successfully reproduces the composition of the acid mixture. Gauss-Seidel least-squares algorithm tends to result in a continuous distribution composed of broader peaks.

View full abstract

The dissolved states of trace metal ions in natural water have been investigated by using the ultrafiltration technique and the combined system of size exclusion chromatography /ICP-MS. The Lake Biwa was chosen as the experimented field. The lake water samples were first filtered with the membrane filter (pore size 0.45μm), and then the filtrate solutions were concentrated by 500-fold with the ultrafiltration filter, which concentrated the large organic molecules with the molecular weight larger than 10, 000. The concentrated solutions thus prepared by ultrafiltration were analysed by size exclusion chromatography with the molecular weight permeation range from 10, 000 to 300, 000, where the chromatograms were detected by the UV absorption detector and ICP-MS. The analytical methods were applied to the vertical profile measurements of the SEC chromatograms in Lake Biwa. In consequence, it has been elucidated that most of metal ions in natural water are in the large organic molecule-metal complex forms.

View full abstract

Ambient air samples were collected in Southeast Asian cities (Beijing, Bangkok, Kuala Lumper and Jakarta etc.) by passive samplers. Sulfur dioxide (SO₂) was analyzed as sulfate ion in solution by FIA with a BaSO₄-immobilized on-line reaction column. The method was based on the reaction of sulfate ion with barium-dimethylsulfonazo-III complex. The results agreed with those obtained by ion chromatography. The results showed that the SO₂ concentrations in theses cities were in the range of 24-140ppb.

View full abstract

On-site analytical methods for the determination of trace amounts of phosphorus and nitrogen in environmental water samples were investigated by using flow injection (FI) technique. Detection reactions used for on-site chemical analysis for ortho-phosphate, nitrite and nitrate were examined. For economizing the reagents and cutting down waste arose along with chemical analysis to enhance zero emission, a micro-flow injection (μFI) technique, in which each flow rate was below one tenth of conventional FI systems and was 50μl min^-1, was investigated fundamentally and applied to on-site analysis, and also a micro-reactor such as a miniature column for the reduction of nitrate to nitrite was developed. To realize the on-site spectrophotometric measurement, an easy-to-move and a one-box type chemical analyzer was newly developed. The analyzer is based on aμFI technique, works with a battery (12V) and can analyze samples rapidly on site with better precision and higher sensitivity than conventional FI systems. For the sensitive determination of phosphate, an ion association reaction of molybdophosphate with Malachite Green was used. Nitrate and nitrite were determined spectrophotometrically on the basis of a diazotization-coupling reaction, where nitrate was reduced to nitrite with a Cd/Cu miniature column prior to the reactions. A newly developed portable micro-flow analyzer was found to be useful for on-site determination of phosphorus as ortho-phosphate at ppb-levels, and nitrogen as nitrite and nitrate at ppb-levels in environmental samples.

View full abstract

A two-step solvent extraction preconcentration procedure in combination with FI-HGAAS is described for the ultra-trace determination of arsenic in environmental samples. Arsenic(III) was quantitatively extracted from natural water sample at pH1.5 in the presence of 10%(m/v) thiourea (masking agent) with 10ml of 0.2%(m/v) zinc hexamethylenedithiocarbamate in 2, 6-dimethyl-4-heptanone (DIBK) and subsequently back-extracted with slight stoichiometry excess . of Cu(II) solution. Total arsenic was extracted using the same procedure after reducing the As(V) to As(III) with sodium thiosulphate. The arsenic concentration in the aqueous back-extracts were determined by FI-HGAAS. The concentration of As(V) was then determined by subtracting the concentration of As(III) from that of the total As. The recovery of As from water samples spiked with 100ng of As(III) and As(V) were 95.5-99.7%. The detection limit (3σ) was 0.008μg l^-1 and the precision (RSD) was 4.5%(n=8) at the 0.5μg l^-1 level.

View full abstract

Based on a kinetic aspect of the extraction of copper(II) with dithizone, the authors have developed a method for the simultaneous determination of the copper(II) complexing capacity of natural water and the lability of soluble copper(II) complex. This method was applied to the artificial samples as well as natural waters containing humic acids. Contribution of humic acid to the copper(II) complexing capacity of natural waters was also discussed From the comparison of labilities of copper(II) complex of both samples with each other, it was found that humic acids play an important role in the complexation of copper(II) in natural environment.

View full abstract

Dibasic calcium hydrogen phosphate (CaHPO₄•2H₂O) and monobasic calcium phosphate (Ca(H₂PO₄)₂•H₂O) are usually mixed with calcium carbonate or phosphoric acid as the raw material to prepare calcium phosphate glass by melting. In this work, the dehydration mechanisms and the activation energies of dehydration of CaHPO₄•2H₂O and Ca(H₂PO₄)₂•H₂O are investigated using nonisothermal TA technique and X-ray powder diffraction patterns.

View full abstract

Multielement profiling analysis was carried out for the 100-m sediment core samples from Lake Baikal to elucidate the paleo-environment. The samples were decomposed by a fusion method using LiBO₂, and major, minor, and trace elements were determined by ICP-AES and ICP-MS. About 50 kinds of elements were determined, and the vertical distributions of the elements obtained for the core samples showed some characteristic features.

View full abstract

To solve the problem of high humidity interfering with the monitoring of organic vapours commonly found in workplace air using the piezoelectric crystal detector, a battery operated fan dryer was incorporated with the P/Z detector to provide a light, sensitive and portable monitor for analysing organic vapours in air. The organic vapour monitor developed is sensitive to analyse organic vapours at ppm levels below the control limits of these vapours. To select a suitable coating for the P/Z crystal detector to be used for diurnal monitoring of organic compounds in indoor air and in factories, eight gas- liquid chromatography coatings was chosen for study. Based on their sensitivity, selectivity, bleeding rate and long term stability towards commonly encountered organic vapours such as 1, 1, 1- trichloroethane, chloroform, benzene and toluene, Apeizon grease L was selected as the coating of the P/Z crystal. The optimised analytical parameters are:temperature 22°C-43°C, relative humidity 40%- 100%, response time 2-30 minutes and linear working ranges 88.8ppm-1880ppm.

View full abstract

The interaction between aluminium ion and tiron (Tr), salicylic acid (Sa), and phthalic acid (Pa) as model compounds for functional groups of fulvic acid in aqueous solution of pH3 was investigated by the ¹³C and ²⁷Al NMR method. In the ²⁷Al NMR spectra peaks due to 1:1 aluminium-ligand complexes were observed at 15.7, 2.6 and -3.5ppm. No peak due to a 1:2 complex was observed. By comparing the ¹³C NMR chemical shifts between free ligands and coordinated ligands, it was evidenced that the three ligands act as bidentate ligands for aluminium ions at pH3. The binding constants of these complexes at pH3 were estimated to be 6×10² (Tr), 3×10²(Sa) and 3×10 (Pa) mol^-1•dm³. These findings show that the stability of these chelate complexes depends on the chelate effect (stability: five>six>>seven membered ring).

View full abstract

Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS) has been applied for the determination of Cd, Cu, Zn and Pb in KRISS B rice flour reference material, which was prepared using the unpolished rice collected from Nonsan, Korea. The ICP-MS instrument used for this work was a laboratory-built unit. The dissolution of rice flour sample was carried out by using a microwave digestion system. The concentrations of Pb, Cd, Cu and Zn in the KRISS B reference material were found to be 29.9ng/g, 33.9ng/g, 3.00μg/g and 22.6μg/g, respectively. In order to validate the analytical results of KRISS B sample, we also analyzed NIES 10-a and NIST 1568 reference materials by using the present method. The analysis results for Cd, Cu and Zn obtained in this work were in good agreement with their certified or recommended values within the limits of uncertainty.

View full abstract