BUNSEKI KAGAKU Abstracts

Recently, there has been keen interest in using metal nanoparticles in analytical chemistry. This review article discusses their sensor applications by focusing on several unique physicochemical properties of metal nanoparticles, especially of gold nanoparticles. Gold nanoparticles have been used in many areas of bioanalytical chemistry through there unique properties, such as extremely high extinction coefficients and straightforwardness in introducing surface functionality. This review article discusses aggregation-based analysis for DNA and other molecules. Also discussed are highly sensitive and selective analytical features of metal nanoparticle assemblies and superstructures with emphasis on electronic sensor applications, which do not require any sophisticated instrumentation or chemical systems, such as optical devices and fluorescent tag molecules. Spectroscopic applications of nanoparticles and their assemblies in the single molecular-level format are also reviewed.

A simple decomposition procedure by a high pressure oxygen combustion method was employed for the determination of six elements (V, As, Se, Cd, Ba and Pb) in coal by inductively coupled plasma mass spectrometry (ICP-MS). Combustion under 3 MPa pressure of oxygen in a sealed bomb is a simple and effective method for the decomposition of carbonaceous materials. Organic components are burnt to form CO₂ and H₂O. Other components also form oxides, which are absorbed in the absorbing solution of a 5 mL of 5％ HNO₃−1％ H₂O₂ mixed solution put in a bomb. To completely decompose the sample, 600 mg of starch is added to 300 mg of a ground coal sample. Though ignition normally takes about 1/2 s, 30 min is required before opening the bomb to keep to the oxides absorbed into the absorbing solution. The accuracy of the procedure was evaluated by comparing the determination value of each element with a certified value of a standard reference material. In this study, NIST SRM 1632c and 1632b, given by the National Institute for Standards and Technology in Washington DC, USA were used as standard reference materials. The results obtained by ICP-MS after high pressure oxygen combustion showed good agreements with the certified values of NIST 1632c for 6 elements (V, As, Se, Cd, Ba, Pb). This method was applied to the determination of 6 elements in coal real samples supplied by CCUJ (Center of Coal Utilization Japan).

The potential-step voltammetric behavior of the reduction and oxidation limiting current of hexacyanoferate ions at a parallel array of microband electrodes or, in short, a stripe electrode, has been studied experimentally with reference to their signal-to-noise advantage. Gold-stripe electrodes of different band widths, that is, electrode B (2a₀＝30 μm, 2b₀＝60 μm) and electrode C (2a₀＝10 μm, 2b₀＝60 μm), 2a₀ and 2b₀ being the width of microband and the distance between the centers of microbands (see Fig. 1), as well as a gold planar electrode of conventional size, electrode A, were examined. The voltammetric behavior was well explained by proposed theoretical equations {M. Senda, Rev. Polarogr., 51, 245 (2005)}: the voltammetric current at the stripe electrode approaches the Cottrellian current with increasing sampling time. Calibration plots were constructed for the concentration range of 2.5〜15 μM of hexacyanoferate. The slopes and intercepts of the regression line of the plots are discussed in terms of the a₀- and b₀-values of the stripe electrode. The signal-to-noise advantage of the stripe electrodes has been shown. The effects of the swelling and smoothness of microband electrodes are discussed.

Simple liquid chromatography by capillary action using a monolithic silica rod and a capillary as the separation media instead of a thin-layer plate in conventional thin-layer chromatography (TLC) was examined. Possibilities of this chromatography were demonstrated by the separation of some organic compounds. Monolithic silica rod and capillary are very handy and useful as separation media for simple open liquid chromatography.

A simple and fast field method was developed for the determination of leachable Cr(VI) in soil by ultrasonic extraction and colorimetry with 1,5-diphenylcarbonohydrazide. Extraction from 2.0 g of a sample with 20 mL of water was accomplished with 30 min under ultrasonication (46 kHz, 15 W). The extraction was repeatable with a relative standard deviation of 10％. The extraction characteristics were discussed based on elution kinetics. The water-leachable concentrations of Cr(VI) or the total Cr were comparable to those obtained by the shaking extraction (6 h) used in Notification 46 of Environmental Agency of Japan. A detection limit of 0.003 mg/L was obtained by a laboratory-made colorimeter with a RGB light-emitting diode. The proposed method is applicable for soil samples containing no Cr(VI)-reducing matters, e.g., humic substances.

The chemical degradation method of polyester-polyurethanes using a high-frequency heating technique was investigated. Model polyester-polyurethanes were prepared from 4,4'-dicyclohexylmethane diisocyanate (H12MDI), poly(butylene adipate) or poly(ethylene adipate)-polyols and isophoronediamine as a chain extender. The number-average molecular weights of their polyesterpolyols were 3500 Da. Phenylisocyanate was an effective reagent to decompose the urethane bond selectively without cleaving the ester bond. After 30 mg of a polyurethane sample was heated at 255°C in a mixture of phenylisocyanate in a sealed glass tube, the urethane bond was decomposed after 30 minutes under this condition. After the reaction, the molecular weight and the composition of the polyesterpolyols were determined by MALDI TOF-MS and SEC. The separation between the peaks of the main series consisted with repeated polyesterpolyols units. The ions consisted of a polyester chain with N-phenylurethane terminal groups from MALDI spectra. SEC chromatograms of degraded samples were consistent with the model N-phenylurethane-terminated polyester. The combination of selective degradation with SEC, MALDI and a high-frequency heating technique, using phenylisocyanate, is a viable method for easy and quick polyurethane polyol characterization.

In this study, we carried out measurements of genotoxic organics, i.e. 11 kinds of polycyclic aromatic hydrocarbons (PAHs), 8 kinds of nitrated polycyclic aromatic hydrocarbons (NPAHs), and 3-nitrobenzanthrone (3-NBA), in diesel-engine exhaust particles (DEP) from combustion processes of biodiesel fuel (BDF) synthesized from vegetable oils, petroleum diesel fuel, and their mixtures. All PAHs and NPAHs in the DEP collected decreased with increasing the content of BDF in the fuel. The reduction rates of PAHs and NPAHs emitted from the diesel-engine by replacing the PDF to BDF were in the range from 44 to 89％. While the reduction rate of 3-NBA, which is one of the oxy-aromatic compounds, was lower than those of PAHs and NPAHs, it was only 20％. PAHs can be generated by the cyclization and/or polymerization of hydrocarbons, especially of aromatic hydrocarbons, when fuels incompletely burn. However, BDF containing 20 vol.％ of benzene showed no increase of PAHs and NPAHs emission compared to the BDF without benzene through the fuel-combustion process. This fact indicates that the drastic reduction of PAHs and NPAHs by using BDF is not due to the content of aromatics in the fuel, but the high oxygen content in its molecular structures. The mutagenic activity of the soluble organic fraction of the DEP also remarkably decreased with increasing of the BDF contents in the fuel. It is apparent from the results that BDF is a quite effective alternative fuel to reduce the genotoxic potentials of DEP.

An evaluation system for the water environment of a river basin (Web-EGIS) has been developed based on a geographic information system. The environmental data were constructed on the Web-EGIS server, enabling us to show the spatial and seasonal variations of the data from client computers via the internet web system. The system also can simultaneously indicate land-utilization information map around the river basin together with the environmental data. This Web-EGIS was applied to the Ongagawa River basin located on the northern part of Kyushu Island, Japan. Spatial and seasonal variations of the environmental data originated from nature and from human activities could be clearly distinguished. The exact pollution point into river water could be specified by using the Web-EGIS system.

The Japan Society for Analytical Chemistry carried out proficiency testing for a fourth-round determination of dioxins (polychlorodibenzo-p-dioxins, polychloro-dibenzofurans and dioxin-like polychlorobiphenyls) in the combustion dust of a waste incinerator. This proficiency testing of analytical laboratories is based on ISO/IEC Guide 43-1, “Proficiency testing by interlaboratory comparisons”. The testing was carried out from June ’03 to August ’03, with the participation of 117 laboratories. As a result, 107 laboratories (91.5％) were estimated as being “satisfactory”, 6 laboratories (5.1％) as “questionable” and 4 laboratories (3.4％) as “unsatisfactory”. A tendency was found that the determined values of the toxicity equivalent quantity became large when an SP 2331 liquid phase or the like was applied to the capillary column of the gas chromatograph. This may have come from insufficient separation of some components.

The Japan Society for Analytical Chemistry carried out a fifth proficiency testing for the determination of dioxins (polychlorodibenzo-p-dioxins, polychlorodibenzofurans and dioxin-like polychlorobiphenyls) in the combustion dust of a waste incinerator. This proficiency testing of analytical laboratories is based on ISO/IEC Guide 43-1, “Proficiency testing by interlaboratory comparisons”. This testing was carried out from June ’04 to August ’04, with the participation of 118 laboratories. As a result, 107 laboratories (91％) were estimated to be “satisfactory”, 6 laboratories (5％) as “questionable” and 5 laboratories (4％) as “unsatisfactory”. The results indicated a tendency that the determined values of the toxicity equivalent quantity became large in the case of applying SP 2331 or CP Sil-88 liquid phases to the capillary column of a gas chromatograph. This may have come from insufficient separation of 1,2,3,7,8-PeCDF, and of 1,2,3,4,7,8-HxCDF from other components.

A novel strategy to integrate various elements necessary for bioanalysis into a microchip was presented for developing a real micro total bioanalysis system. This dissertation focused on the integration of reaction fields into a microchip, the integration of chemical functions into a microchannel, and the integration of a detection system into a microchip. The integration of immunoassay into a multi-channel microchip dramatically shortened the analysis time while reducing the amounts of the reagent and sample. Photochemical patterning of protein inside a microchannel allowed an expression of different chemical functions in a microchannel. The fabrication of an integrated microchip incorporating an LED and an optical fiber led to miniaturization of the entire analytical system, which enabled an on-site analysis. The techniques developed in this study would be useful for developing a real micro total bioanalysis system.