Kin-ichi Tsunoda

The Possibility of Signal Enhancement in Liquid Absorption Spectrometry with a Long Capillary Cell Utilizing Successive Total Reflection at the Outer Cell Surface

A new type of long capillary cell (LCC) for liquid absorption spectrometry, in which incident light is transmitted with successive total reflection at the outer cell surface, has been proposed. An uncoated and uncovered capillary tubing of borosilicate glass showed much better light trans-missivity in aqueous solution as a LCC than did one with mirrored walls, and it could be used in coiled form without attenuation of light. An effective pathlength of 85 cm (at A1 cm = 9 × 10−5) and a baseline stability of 3 × 10−6 AU were obtained with a 90-cm LCC (i.d. 260 μm, o.d. 400 μm, coiled into 14-cm-diameter coil). The calibration curve was nonlinear because of its nature as a multipath cell. The distribution of light energy inside the LCC was estimated by using a simple statistical model based on the Markov chain.

Seasonal change in the level and the chemical forms of aluminum in soil solution under a Japanese cedar forest

The level of dissolved aluminum and its chemical forms in soil solutions consecutively collected by a porous cup vacuum sampler were monitored over a period from January 2001 to December 2001 at a Japanese cedar (Cryptomeria japonica) forestry area susceptible to acid deposition to characterize current soil dynamics and to evaluate potential tree damages. Distinction and characterization of Al species with differential toxicities were performed by two complementary speciation techniques; cation-exchange HPLC with fluorometric detection using 8-hydroxyquinoline-5-sulfonic acid (HQS) and size-fractionation/inductively coupled plasma atomic emission spectrometry (ICP-AES). The concentrations of free Al (mainly Al3+ and Al(OH)2+) and inert Al (existing as the complexed and/or colloidal forms) ranged between 0-150 microM and 10-50 microM, respectively. The concentrations of inert Al were mostly below 40 microM during an annual cycle and showed no marked seasonal variation, while free Al concentrations showed a clear tendency to increase in the spring and summer seasons (in the period from April to August) probably due to the enhanced activity of microbial nitrification and the resultant soil acidification. Major cations and anions were also regularly determined and their seasonal changes were correlated with that of the dissolved Al concentration. Correlations between total Al (mainly existing as free Al) and the related species (and environmental conditions) were as follows: Al and Mg (R=0.96, P<0.01), Al and Ca (R=0.97, P<0.01), Al and NO3- (R=0.68, P<0.01), Al and temperature (R=0.68, P<0.01), Al and solution pH (R=-0.61, P<0.01), solution pH and NO3- (R=-0.65, P<0.01).

Adsorption of Methylene Blue onto Silylated Silica Surfaces, Studied Using Visible Attenuated Total Reflection Spectroscopy with a Slab Optical Waveguide

The behavior of methylene blue (MB) molecules at silica/water and silylated silica/water interfaces was examined using visible attenuated total reflection spectroscopy with a slab optical waveguide (SOWG). An alkyl silane coating changed the adsorbed form of MB on the surface from a dimer (λmax = 600 nm, bare silica surface) to a monomer (λmax = 670 nm), and the carbon number of the silylation reagent influenced the amount of adsorption and the orientation of the molecule. Moreover, the addition of an anionic surfactant, dodecylbenzenesulfonate (DBS), caused the deposition of MB/DBS ion pairs, which gave an identical attenuated total reflection (ATR) spectrum to that of the dimer. Linear dichroism measurements revealed that the ion pairs were adsorbed onto the silylated silica surface randomly in terms of the orientation angle of MB, while the MB monomer was strongly oriented, i.e., the direction of the transition moment of MB roughly parallels the surface plane. This difference in the orientation angles of the adsorbed species can be utilized for their selective detection using polarization SOWG measurements.

Application of the glass slab optical waveguide to the spectrophotometric determination of the iron(II) : 1,10-phenanthroline complex by flow analysis

Abstract A slab optical waveguide (SOWG) absorption detector was applied to the determination of the orange-red Fe(II)—1,10-pheranthroline complex [Fe(phen) 3 ] 2+ by flow analysis. When a sample solution containing [Fe(phen) 3 ] 2+ was introduced into a flow of sodium dodecylbenzene sulphate (DBS − ) solution, an ion pair of [Fe(phen) 3 ] 2+ and DBS − was formed in a mixing coil, and was then adsorbed on the glass SOWG. The adsorbed ion pair caused the attenuation of light of a green He-Ne laser(543.5 nm) or of an Ar ion laser (multi-line, mainly 488 nm and 515 nm). The best sensitivity was obtained with a glass SOWG fabricated by a radio frequency sputtering method, which was 9.5 times higher than that with a conventional spectrophotometer (1-cm cell) for a 0.5-ml sample solution.

The Use of Poly(tetrafluoroethylene-co-hexafluoropropylene) Tubing as a Waveguide Capillary Cell for Liquid Absorption Spectrometry

An optical waveguide capillary cell (OWCC) has been used for signal enhancement in Raman scattering spectroscopy, colorimetry, and fluorometry. When the cell, hollow capillary tubing, is filled with a solvent that has a refractive index higher than that of the cell material, it forms a liquid-core optical fiber and it can be elongated to extreme length. Table I summarizes the refractive indices of various organic solvents and cell materials. As shown in the table, when capillary tubing made of borosilicate glass or quartz glass is used, only a few organic solvents such as carbon disulfide and toluene can be used—which greatly limits the applicability of this method.

The host-binding domain of the P2 phage tail spike reveals a trimeric iron-binding structure

The adsorption and infection of bacteriophage P2 is mediated by tail fibres and tail spikes. The tail spikes on the tail baseplate are used to irreversibly adsorb to the host cells. Recently, a P2 phage tail-spike protein, gpV, was purified and it was shown that a C-terminal domain, Ser87-Leu211, is sufficient for the binding of gpV to host Escherichia coli membranes [Kageyama et al. (2009), Biochemistry, 48, 10129-10135]. In this paper, the crystal structure of the C-terminal domain of P2 gpV is reported. The structure is a triangular pyramid and looks like a spearhead composed of an intertwined β-sheet, a triple β-helix and a metal-binding region containing iron, calcium and chloride ions.

Liquid/Liquid Optical Waveguides Using Sheath Flow as a New Tool for Liquid/Liquid Interfacial Measurements

A liquid/liquid optical waveguide was constructed using a sheath flow. Since the refractive index of an organic solvent is generally higher than that of water (nD = 1.33), light introduced into the inner organic flow should proceed with total multi-reflection within the inner flow, so that the inner part of the sheath flow acts as the core of an optical waveguide. This sheath flow liquid/liquid optical waveguide was stable and showed no substantial background scattering. Moreover, it is applicable to both miscible and immiscible liquid/liquid interfaces. Thus, it may become a new tool for studying liquid/liquid interfaces as well as for sensitive optical measurements.

Sensitive measurement of methylene blue active substances by attenuated total reflection spectrometry with a trimethylsilane-modified glass slab optical waveguide

Attenuated total reflection spectrometry with a slab optical waveguide (SOWG) was explored for the simple, rapid and sensitive measurement of total anionic surfactants by the methylene blue active substance (MBAS) method. A fused-silica sheet used as a guiding layer was modified with trimethylsilane (TMS) to extract and concentrate the MBASs on the SOWG surface. Based on preliminary studies of the adsorption behavior and visible ATR spectrum of MB on the modified silica surface, a detection wavelength of 600 nm was chosen for the sensitive measurement of anionic surfactants. When the concentration of MB was set at 10 microM in the final measurement solution, the calibration curve for a typical anionic surfactant (sodium dodecylbenzenesulfonate) was linear up to 0.6 microM and the detection limit was 0.07 microM. The proposed method was applied to the determination of total anionic surfactants in river water.

Environmental monitoring of historical change in arsenic deposition with tree bark pockets

ICP-MS analysis recorded historical change (c. 1846 to 2002) in the arsenic concentration of bark included within the trunks (tree bark pockets) of two Japanese oak trees (Quercus crispula), collected at an elevated location approximately 10 km from the Ashio copper mine and smelter, Japan. The arsenic concentration of the bark pockets was 0.016 +/- 0.003 microg cm(-2) c. 1846 (n = 5) and rose 50-fold from c. 1875 to c. 1925, from approximately 0.01 to 0.5 microg cm(-2). The rise coincided with increased copper production in Ashio from local sulfide ores, from 46 tons per year in 1877 to 16,500 tons per year in 1929. Following a decline in arsenic concentration and copper production, in particular during the Second World War, a second peak was observed c. 1970, corresponding to high levels of production from both local (6,000 tons per year) and imported (30,000 tons per year) ores, smelted from 1954. Compared to the local ores, the contribution of arsenic from imported ores appeared relatively low. Arsenic concentrations declined from c. 1970 to the present following the closure of the mine in 1974 and smelter in 1989, recording 0.058 +/- 0.040 microg cm(-2) arsenic (n = 5) in surface bark collected in 2002. The coincident trends in arsenic concentration and copper production indicated that the bark pockets provided an effective record of historical change in atmospheric arsenic deposition.

Characteristics of potassium ion-doped glass slab optical waveguide as an absorption cell and its application to the spectrophotometric detection of Methylene Blue

The characteristics of a K+-doped glass slab optical waveguide (SOWG) as an absorption cell are discussed in terms of effective path length (Leff) and relative sensitivity (S/cm). The longest Leff value of 11 μm was observed with TM0 mode of the SOWG with a 30-min ion-exchange process in molten KNO3, which was in good agreement with the calculated value of 9.7 μm. The K+-doped SOWG provides higher sensitivity by one to two orders of magnitude than conventional absorption measurements of an analyte on a glass surface to which perpendicular irradiation of source light on the surface is applied. Octadecylsilane modification of the SOWG surface was effective for the sensitive detection of Methylene Blue by flow analysis where an ion pair of Methylene Blue and lauryl sulphate was formed.