BUNSEKI KAGAKU Abstracts

Volatile organic compounds (VOCs) contribute substantially to the formation of ozone and other photochemical oxidants. Some VOCs have been identified as toxic or mutagenic pollutants. Then, a simple analysis of VOCs at low levels in the atmosphere was conducted using passive samplers, and the annual changes and origins of VOCs in Kyoto were analyzed. Furthermore, a portable, time efficient and sensitive instrument for the continuous analysis of VOCs was developed in order to elucidate the human health risk and environmental load, and was applied to indoors and environmental monitoring.

The production technique of gold ground of a pair of folding screens by Ogata Korin, "Red and White Plum Blossoms," was investigated by using combined on-site analytical methods. In a previous study of this screen, it was pointed out that the gold ground of the screen was produced by the coating of gold paint, not an overlay of gold leaf, based on X-ray fluorescence analysis. However, there was no certain evidence of the presence of gold paint on the screen. The purpose of this study was to reveal the production technique of the gold ground of this screen by introducing new analyzing methods. We especially focused on a preferred orientation of Au crystals in the gold leaf. Since Au crystals are oriented along (100) plane in the gold leaf, X-ray powder diffractometry could be useful to distinguish between gold leaf and gold paint. We brought following three instruments : a digital microscope, a portable X-ray fluorescence spectrometer and a portable X-ray powder diffractometer to the MOA Museum of Art. They were used for nondestructive on-site analysis of the screen. Characteristic membrane-like shape was microscopically observed on the gold ground of the screen. X-ray powder diffraction patterns of the gold ground of the screen showed a strong preferred orientation parallel to the (100) plane. We also analyzed a reference picture painted with gold paint and found a striking difference between the gold paint and the gold ground of the screen. We carried out line analysis by using an X-ray fluorescence spectrometer, while focusing on a checkered pattern on the gold ground of the screen. The intensity of Au-L lines of the checkered area was a few times stronger than that of the ground part. Therefore, it was indicated that the checkered area was produced by overlapping of two gold leaves on the screen. From these observations, we have concluded that the gold ground of the screen could be produced by the gold leaf.

A novel analytical instrument has been developed for simple near-real time measurements of isoprene, and was applied to on-site analysis of forest air. Isoprene contained in sample air was trapped for 4 min and thermally desorbed to introduce it into a chemiluminescence cell. In this single column trapping/separation chemiluminescence (SCTS–CL) method, isoprene in ppbv level could be measured every 10 min with a limit of detection of 0.15 ppbv. In a plant chamber experiment, the isoprene concentration increased with light irradiation and decreased in the dark. The chamber experiment results by SCTS–CL agreed well with those obtained by thermal desorption-gas chromatography-mass spectrometry. In field analysis conducted in forest, isoprene concentration increased in the daytime and not found in the nighttime. On the other hand, α-pinene concentration was higher during the night compared to that in the day ; probably because α-pinene emitted whole day and its decomposition was higher during the day. Other than isoprene, formaldehyde, ozone, nitrogen oxides, organic and inorganic acids were monitored simultaneously in the forest campaign, and daily variations and seasonal variations are discussed. Model of emission and decomposition was considered and daily variation of emission rates were simulated from changes in the concentrations of isoprene and α-pinene. The amplification of oxidants by BVOCs is discussed based on the field experimental results.

We developed a redox potential array sensor that can measure rhizosphere and the soil redox potential with microscale (μm level) two-dimensionality in paddy soil. The redox potential array sensor comprises a reference electrode available on the market, a voltmeter, and a working electrode. The working electrode flatly arranged the Pt electrode in the 5×5 Si substrate. First, to confirm the accuracy of the sensor output, a redox potential standard solution (Compound of quinhydrone and potassium hydrogen phthalate) was measured with the developed sensor. Next, we were able to measure the reduction process of the paddy soil around rice grain by monitoring the two-dimentional redox potential of the soil by the redox potential array sensor and to obtain a lower redox potential around a rice grain. We examined the oxidation process around the rice root (rhizosphere) in paddy soil by using redox potential array sensors. The redox potential of the soil around the rice root was much higher than that of the soil separately-placed from the rice root during a measurement. These results indicate that we can measure two-dimensional oxidation-reduction changes of soil or rhizosphere using the redox potential array sensor.

An on-site visual colorimetry for dissolved manganese at several tens of ppb levels in water was proposed. Purple-colored MnO₄⁻ oxidized from dissolved manganese by IO₄⁻ was concentrated on surface of a nylon membrane filter with benzethonium ion (Ben⁺) during filtration. IO₄⁻ added as an excessive oxidizing agent forming an emulsion particulate ion-associate phase (IAP) with Ben⁺, and MnO₄⁻ · Ben⁺ was extracted into the IAP. Their behavior suggests that MnO₄⁻ is retained on the filter as a form of the IAP. The filter after the retention turned purple colors depending on the amount of MnO₄⁻ ; hence, a visual colorimetric determination of manganese by comparing with standard color charts was readily conducted. The proposed devices, a sealed polyethylene tube packed with reagents and filtration apparatus with membrane filter in 4.0 mm diameter of filtration area, were brought together as a kit for on-site analysis. Manganese at 0.02 - 1 mg L⁻¹ in 1.5 mL of sample was able to be determined within about 3 minutes of the entire procedure. Results from river and well-water samples were successfully obtained in good agreement with those by ICP-MS. The proposed colorimetry is useful screening tool for Drinking Water Quality Standard in Japan, 0.05 mg L⁻¹.

Liquid electrode plasma atomic emission spectrometry (LEP-AES) is a compact elemental-analysis method, which requires no plasma gas and no high-power source, and is suitable for on-site portable analysis. In this paper, the LEP-AES is combined with the concentration method using liquid organic ion associate extraction, and a concentration/simultaneous determination method for trace metals (Cu, Mn, Pd, Zn, Cd and Pb) in water is developed. Metals were converted into a complex with a chelating reagent in a 40 mL sample solution, and were extracted into a liquid ion associate during phase formation. The volume of the ion associate was μL-scale. The ion associate was dissolved with 400 μL of a 50 vol% methanol+0.1 M HNO₃ solution, followed by detection by LEP-AES using 40 μL of the sample. As a results, a liquid organic ion associate extraction enabled a 100-fold enrichment of trace metals, and improved the detection limits (3 σ) by a few μL L⁻¹ – sub mg L⁻¹. Interestingly, for some metal elements, the magnification of the total sensitivity combined with LEP-AES resulted in more than 1000, which is more than the value of 100-fold for the enrichment. This method was applied to the determinations of Cu, Mn, Zn, Cd and Pb in certified reference materials (EnviroMAT EU-H-1 waste water). The values obtained in this method were nearly equal to the certified values.

A method for simply measuring water mixed into oil is restricted. In the present study, we synthesized a solvatochromic organic fluorescence dye. Changes in the fluorescence spectra and the luminescent color to change of the amount of water in the oil of this fluorescence dye were investigated. In dioxane, which is a low dielectric constant solvent, the color changed from green to yellow and a bathochromic shift of the fluorescence spectra was observed by the increase in moisture. These results suggested that the water selectively solvated to the fluorescence dye. On the other hand, in acetonitrile, which is a high dielectric constant solvent, the bathochromic shift observed by the increase in water showed almost the same tendency as the bathochromic shift accompanying the increase in the dielectric constant. However, the color showed only yellow in a visible observation. The visual detection of water will be applied to some low-dielectric organic solvents and lubricating oils.