The autocatalytic reaction shows a dynamic color change after a certain induction period. In addition, the induction period of the reaction changes depending on the concentration of substances. Therefore, by using an autocatalytic reaction, it is possible to quantify by measuring the time with the human eye and a stopwatch. This method enables visual measurement with higher sensitivity and accuracy than the visual measurement method based on the conventional colorimetric method. However, it is necessary to keep observing the solution at all times during the measurement. In this study, we attempted to automate an analysis with a autocatalytic reaction using a smart device by developing an application software that automatically measures the induction period of the autocatalytic reaction. In this paper, the analytical performance was evaluated using a method for measuring the concentration of iron(II) ions by an autocatalytic reaction with sulfite and hydrogen peroxide. As a result, iron ion could be automatically determined with the proposed method. Moreover, this proposed method could be utilized under several kind of conditions, such as various distance, irradiation levels, and temperature.

Raman spectroscopy can obtain spectral information strongly reflecting the molecular structure in a non-destructive manner, and near-infrared (NIR) spectroscopy can simultaneously analyze molecular composition, molecular concentration, and the interaction between the biomolecules such as proteins and water. By using both spectroscopies in a complementary manner, interdisciplinary research of analytical chemistry, physical chemistry, and biophysical chemistry have been achieved. In this review, three topics of my recent research are introduced. The first one is about non-staining in situ imaging of medaka fish eggs using NIR spectroscopy. The activation of egg development was captured by detecting the changes of the hydrogen bond network of water molecules, and optical interferences caused by Doppler effect made it possible to get blood flow images of fish embryos. With respect to the second topic, it was revealed that the mouse oocyte maturation and the embryonic quality were able to be assessed in situ by Raman spectroscopy. The concentration of lipids and phosphoric acids could be biomarkers for discriminating fertilization and viability competences of embryos, and the results presented a new possible evaluation method of embryonic quality to assisted reproductive technologies. As for the third topic, the distributions of lycopene aggregations within tomato fruits were visualized using resonance Raman imaging. J- and H-aggregates were distributed in layers under an exocarp, and the linear relationship between the frequencies of Raman band (ν₁) and the electronic transition energy (S₀→S₂) shifted by forming aggregations was interpreted in terms of differences of effective C=C chain length. Since these spectroscopic imaging methods can obtain biomolecular information as they are, the methods are expected to be further applied to various fields such as medical treatment, pharmaceuticals, bioscience, and food engineering.

Mid-infrared spectroscopy has an extremely high sensitivity to water, making it a powerful tool for the examination of trace amounts of water in solid polymers. This method does not provide thermodynamic parameters directly unlike calorimetry, which is the most widely used method to examine the state of water in water-polymer systems, but it has the advantage of in-situ measurement and provides information reflecting molecular orientation and hydrogen bonds between water molecules and between water molecules and polymer. This paper outlines various methods for measuring and interpreting the vibrational spectra of water in solid polymers by mid-infrared spectroscopy. In the first part of the paper, the water structure in solid polymers by transmission and attenuated total reflection methods at room temperature will be discussed and we will describe the spectral form reflecting the hydrogen bonding sites in the polymer chain and irremovable water in the polymer matrices. In the second half of the paper, condensation, solidification, deposition, sublimation, melting, and evaporation of water in solid polymers as revealed by variable-temperature mid-infrared spectroscopy will be discussed, as well as deposition during the rewarming process (re-deposition), which was confirmed for the first time by this method.

Kuantan is the state capital of Pahang and the 17th largest city in Malaysia. The Kuantan District Locality Plan 2004–2015 identified Kuantan as one of the country’s future growth centers and a hub for trade, commerce, transportation, and tourism, owing to its strategic location on the east coast. Following the implementation of the locality plan over the past decade, the area has developed rapidly, resulting in environmental degradation. To assess water quality and identify polluted areas in the region, we measured the water chemistry and microbial activity in response to land-use changes for four major rivers, namely, Pahang, Kuantan, Belat, and Galing, using data from ion chromatography for inorganic ionic species and portable water quality monitoring devices to measure several water parameters. From the obtained results, the following were concluded: (1) due to the low anthropogenic wastewater pollution, the dominant microbial reactions in the Pahang, Kuantan, and Belat rivers were aerobic microbial oxidation of organic compounds and nitrification by nitrifying bacteria, allowing the rivers to self-purify; (2) the Galing River predominantly experiences anaerobic decomposition of organic compounds through microbial denitrification and sulfate reduction due to the heavy anthropogenic land use in the river; and (3) the western side of the Galing River and upstream sites located within the industrial and business/servicing areas in the Kuantan city center experience the heaviest pollution.

A gold-deposited square glass rod sensor system capable of performing measurements on two adjacent faces independently based on surface plasmon resonance (SPR) was developed. The sensors have gold layers with different film thicknesses of 0 and 45 nm, or 30 and 70 nm on two surfaces. The responding surface can be selected by the use of the polarized light, which has an electric field perpendicular to each surface. When the cross-sectional size of the glass rods was the same, the SPR peak shifted to a higher refractive index as the gold film thickness increased. This finding agreed well with the previously reported response properties of the round glass rod sensor. On the other hand, as the cross-sectional size of the glass rod became larger, the SPR peak tended to shift to a lower refractive index. It is thought that the thicker the glass rod, the wider the angle range of light in the sensor. The response curves of the sensors were compared with the theoretical curves calculated using multi-layer Fresnel equations. The experimental response curves were broad and downward-sloping compared with the theoretical ones. It is suggested that the experimental system may have a more complicated light path than that of the theoretical. However, the dips of the response curve due to the SPR absorption agreed well with the theoretical calculations. Simultaneous and independent measurements of two adjacent faces of the square glass rod were achieved by using a polarizing beam splitter instead of the polarizing plate. It was found that the response of the one face slightly affected the other face depending on the optical arrangement.

Radioactive cesium (¹³⁴Cs and ¹³⁷Cs) originating from the Fukushima Daiichi Nuclear Power Plant accident was detected in the Tama River watershed. Previous investigations have shown that the concentration of ¹³⁷Cs in sediments sampled at the Nogawa River was higher than that of the main stream. In addition, a good correlationship was obtained between the concentration of ¹³⁷Cs in sediments sampled at the Nogawa River and the ignition loss of the sediment. These results suggested that the organic matter is an important factor in the discussion of the environmental dynamics of the radioactive cesium in the Nogawa River. Results of TG/DTA and Py-GC/MS have suggested that the existece of lignin and organic compounds were detected only in the upper reaches. In this investigation it is suggested that radioactive cesium attached to lignin in the upper reaches decomposed and released into the river as it migrated downstream.

Chemical analysis of individual fine particles was conducted using an ICP-MS technique utilizing a time-of-flight type mass spectrometer (ICP-TOF-MS). The elemental composition and size of individual particles were derived from the signal events emanating from the single particle, and the ion signals covering a wide mass range (e.g., ²³Na to ²³⁸U) were acquired. To evaluate the reliability of the resulting elemental data obtained, elemental analysis was conducted on the nanoparticles (NPs) obtained from standard material (standard rock JG-1) produced through the laser ablation in liquid technique. For data processing, an in-house software “NP Shooter” was developed. The individual elemental compositions of the fine particles produced from the rock samples were plotted on ternary graph plotted by Si-Al-(Fe+Mg), and thus the chemical composition of individual particles can be visually identified. The data points plotted on the ternary graph reflects the chemical composition of the original materials subsidized in this study. Another important feature of the present analytical protocol is that the size of individual particles was also shown on the vertical axis of the ternary graph (triangular prism graph), and thus, the correlation with the chemical composition and size of the particles can also be decoded. The combination of the ICP-TOF-MS technique and in-house software can be used as a major analytical tool for the provincial study for various fine particles such as environmental aeolian dusts, small solid phase contaminants, or cosmic nanoparticles.

In flow injection analysis (FIA), the baseline noise of the detection signal is an important parameter that determines the detection sensitivity. In this study, we applied the Fourier analysis/inverse Fourier analysis of Microsoft Excel to the detection signal of FIA to decrease the noise signal. The Fourier analysis of the detection signal for a sample of 0.06 mg L⁻¹ NO₂⁻ showed many frequency components with amplitudes less than 0.04 mV. After removing these frequency components, inverse Fourier analysis was applied, and a smooth detection signal was obtained. Even with a sample of 2.50 mg L⁻¹ NO₂⁻, the noise signals were successfully removed using the Fourier/inverse Fourier analysis. The signal-to-noise ratio (S/N) of NO₂⁻ was improved by ca. 15 times. We concluded that removing noise signals by Fourier analysis effectively improves the S/N of FIA.

In this study, we developed a cell culture device using gelatin. An appropriate material was sought to be used as a mold for the gelatin gel, and the bonding method between the gelatin gel and the coverslip, which was the cell culture surface, was investigated. The developed device can be used with a high-magnification objective lens. Furthermore, we report that human vascular endothelial cells and fibroblasts were co-cultured in the gelatin device, and a capillary network was successfully constructed.