BUNSEKI KAGAKU Abstracts

How do water molecules behave at the electrochemical interface (the charged electrode-electrolyte interface)? This is one of the most fundamental and important questions in electrochemistry, and has been discussed extensively since the first proposal of the electric double layer model by Helmholtz in 1853. In the 1960s, a general consensus was reached that water molecules orient along the electric field at the interface and change the orientation depending on the applied potential (i.e., surface charge). However, details had long been unclear. Recent developments of computational theoretical chemistry and in situ surface analytical techniques have enabled a further detailed study of the interface at a molecular level and renewed our understanding. Recent progresses has been reviewed in the manuscript by focusing on experimental data provided by surface-enhanced infrared absorption spectroscopy (SEIRAS).

A charge-transfer dye, anilinonaphthalene sulfonate (ANS), shows a drastic change in its fluorescent properties, depending on the change of surrounding microscopic environments. From the characteristic fluorescent features, ANS has often been applied to measurements of solvent microproperties at local environments. Since the fluorescent intensity of ANS drastically increase in hydrophobic environments compared to in water, ANS has been widely used as a hydrophobicity probe for several decades. On the other hand, ANS has also been applied to a micropolarity probe, utilizing its change in fluorescent wavelength, which depends on the solvent polarity. Here, we show a new application of the ANS. Our current study has revealed that the fluorescent lifetime of ANS sensitively reflects the microviscosity. From the results, we proposed a new application of ANS as a microviscosity probe, and applied it to measurements of the microviscosity of water in biologically important systems. The important point is that the microviscosity is probed by the fluorescent lifetime, not by the intensity. Lifetime measurements are free from the difficulty of discriminating of the origin of the intensity change, which is due to both the change in the local properties and localization of the probe molecules. This merit is important for applications of the florescent probe to inhomogeneous systems, such as water in polymer gels, material interfaces, and in living cells.

In the far ultraviolet (FUV) region (120-200 nm), absorption bands due to transitions of outer orbital electrons have been observed. These absorption coefficients are so large that the uses of FUV spectroscopy had been limited involving applications to gases and reflectance on solid surfaces. We developed FUV spectroscopy method designed for the purpose of measuring of liquid by using attenuated total reflection (ATR) with nitrogen gas purge. The ATR-FUV spectrometer reveals the features of the FUV spectra of liquid samples. The first electronic transition band of water, which shows systematic change with the state of hydrogen bonding, had become a good candidate of this system. This paper describes the ATR-FUV analysis of aqueous solutions and the related basic properties of the UV and FUV spectra of water.

The water content of rice cracker was measured by a milled and dry-weight method, and was predicted by a linear regression analysis at a peak around the 1917 nm by a near infrared (NIR) spectrum using a portable NIR spectrometer after a spectra-pre-treatment. The correlation between the value by the dry weight method and the NIR predicted value was r² = 0.946. Therefore, predicting the water content of rice cracker was possible using a portable NIR spectrometer. The water content could be measured even from the outside of a plastic bag. By an analogy of a Clausius-Clapeyron equation, ∂(lnw)/∂(1/T/K) = ΔH/R (w ; water content, ΔH ; vaporization enthalpy change) is obtained. The water content of four kinds of rice cracker at 20-135°C was measured and ΔH for the rice crackers were obtained from the slope of plots of (ln [w/mol/kg]) vs. (1/T/K). The result shows that one can discuss the hydroscopic difference between rice crackers from the ΔH.

Liquid chromatography (LC) with a pre-column derivatization method has been developed to measure the concentrations of aminopolycarboxylic acids (APCAs ; ethylenediamine tetraacetic acid, nitrilotriacetic acid, and diethylenetriaminepentaacetic acid) in water samples. This method is based on an intramolecular excimer-forming fluorescence derivatization with 4-(1-pyrene)butylamine (PBA), followed by phenyl-modified reversed-phase LC. The derivatization reaction of APCAs with PBA was significantly affected by the presence of metal ions in the samples. Therefore, nitrilotrismethyl phosphoric acid, an alternative chelating agent of APCAs, was used to stabilize the reaction in this study. The accuracy obtained for the detection of APCAs in spiked tap water and commercial mineral water samples at concentrations of 50, 500 and 2000 μg L⁻¹ was 98-108% within 3.3% as the relative standard derivation.

A huge plain, called the “Saga Plains”, exists in Saga Prefecture, Japan. This plain has been made by reclamation from the Ariake Sea. The inhabitants of the southern area of the Saga Plains depend on the ground water from deep-drilled wells for living and agricultural purposes. Several deep-drilled wells exist in this area. Recently, use of ground water has been reduced, because water conveyance from the river was carried out. For the last 23 years, the chemical components of this ground water have been measured. In 1994, a considerable amount of ground water was pumped out, and the water level reduced substantially due to drought. The water level recovered after two years (1996). “Nui-no-ike” is a pond of spring water at the foot of Mt. Kishima. The supply of spring water to this pond stopped approximately 40 years ago, and the pond dried up. In 2001, the water supply resumed. The direction of ground water was examined using measurement data of chemical components in 1994 and 1996 for the spring water group “Nui-no-ike”. It was suggested that the ground water in the south area of Saga Plains was not influenced by Ariake Sea from these data. The chemical components of the ground waters were similar to those of “Nui-no-ike”. Hence, it was suggested that the ground water was supplied from near the foot of Mt. Kishima.

A depth profiling analysis with x-ray photoelectron spectroscopy (XPS) and measurements of a surface roughness with scanning probe microscopy (SPM) were performed on the surface of polymethylmetacrylate (PMMA) etched by electrospry droplet impact (EDI). The roughness increased, whereas no substantial changes were observed in the ratio of the four functional groups as well as in the ratio of the carbon and oxygen on the surface of PMMA with increasing etching time. The proposed mechanism of a etching due to EDI is as follows : the impact of charged water droplet accelerated at 10 kV with sizes of about 107 u causes a shock wave to the target specimen ; the shock wave induces the detachment of atoms or molecules from its surface. No preferential detachment of functional groups was observed in the present specimen ; PMMA, the observation of which established that the technique of EDI could be used as an ideal method of main chain unit etching without damage. As a result, it was observed that this EDI etching was a useful method for XPS depth profiling of various polymers.

In low-pressure argon laser-induced plasma spectrometry, variations in the emission intensities of iron and chromium spectral lines in iron-chromium binary alloy were investigated to obtain a good calibration curve for the quantitative analysis when the experimental parameters for the laser irradiation were optimized. By measuring the temporal variation both in the intensity ratios between iron and chromium emission lines and in the excitation temperature for the atomic lines of iron, it was found that the excitation mechanism of the neutral atomic lines would be different from that of the singly-ionized lines. A linear calibration curve for chromium over a wide concentration range could be obtained when atomic or ionic line pairs of chromium and iron whose excitation energies were similar were employed.

The determination of total nitrogen in fish meal by the Kjeldahl method under the Official Method of Feed Analysis in Japan was studied in comparison to the Dumas method. There were significant differences in several samples between the methods. In order to obtain the optimum digestive condition, the added amounts of catalyst and the boiling period after the liquid became clear were examined using L-lysine-HCl. The optimum conditions for the digestion of 1 g of fish meal were found to be adding 30 mL of H₂SO₄ and 10 g of catalyst (9 g K₂SO₄, 1 g CuSO₄ · 5H₂O), and boiling for 120 min after a clear liquid is obtained in traditional digestion by a gas heating device. Two sets of data by the Dumas and Kjeldahl method under the optimum digestive condition were tested with a two-sided Welch test. The mean values indicate that the Dumas method tends to produce a result that is slightly higher than the Kjeldahl method, however, there were no significant differences between these methods. The Dumas method had excellent precision, and was as reliable as the Kjeldahl method under the optimum digestive condition. The differences are unlikely to be attributable to any contribution from inorganic N, such as nitrate and nitrite, but are related to incomplete digestion by the Kjeldahl method under non-optimum conditions as shown by poor recoveries of organic nitrogen compounds such as lysine in fish meal.

Microscopic studies on laser-induced fluorescence emitted from asbestos (chrysotile) and a building material (glass-wool : an alternative material for asbestos) fibrous particle excited by a ultra-violet (266 nm) laser, have been conducted in an attempt to discriminating asbestos from the other materials. Significant differences in the decay ratio and intensity of the fluorescence were observed between those fibrous particles. The result obtained in this experiment shows that microscopic analysis using the difference in the fluorescence characteristics can be useful for identifying asbestos particles from other building materials under a microscope.

For the development of a sensitive and accurate immunosensor, the production of a highly specific surface to the corresponding antibody is essential. Moreover, a specific surface having good reusability is worthwhile for constructing a prompt auto-monitoring immunosensing system. In this study, antigen analogous-modified gold substrates having a specific adsorption property to an anti-dioxin antibody, were prepared by the immobilization of 2,4,5-trichlorophenoxy (TCP) derivatives on a gold surface using various methods. An anti-dioxin antibody, which has a good correlation immunoaffinity with the total toxic equivalent quantity (TEQ) of polychlorinated dibenzo-p-dioxins, was employed as a specific antibody, and the specification of the surface was evaluated by a comparison of the surface plasmon resonance (SPR) responses to a specific anti-dioxin antibody and non-specific anti-hemoglobin antibody. In order to obtain a firm and stable immobilization of TCP, a carboxyl group was introduced on gold by a self-assemble monolayer (SAM) technique, and TCP derivatives were attached to the SAM surface with covalent bonding directly and indirectly through the presence of a hexamethylene chain, bovine serum albumin (BSA), and ethylene glycol oligomer (EGO). A TCP derivative-immobilized substrate, prepared using BSA, showed poor reusability. A TCP derivative-immobilized substrate having EGO was highly specific to an anti-dioxin antibody, while that prepared by the direct immobilization of TCP and with introduction of a hexamethylene chain presented nonspecific adsorption. In addition, a TCP derivative-immobilized substrate having EGO showed a good reproducible response from the second repetition, and was reusable more than seven times.

For the radiochemical analysis of low-level radioactive wastes, a relatively large quantity of sample solutions must be prepared. In order to dissolve incinerated ash (fly ash and bottom ash) of radioactive combustible wastes and cement-solidified products of radioactive liquid wastes, a dissolution method using microwave heating devices was developed. In the present method, most metal elements in samples were extracted with HCl and HNO₃ to the sample solution and a precipitate with silica as the main ingredient was decomposed with HF and HNO₃. As a result, the fluoride residue was sufficiently reduced and more than 99% of the radionuclides were recovered to the sample solution. The ash and cement-solidified product samples were successfully dissolved in a shorter time compared with that of a conventional method by external heating, because HClO₄ with a high boiling point and having much time for heating to dryness was not used.