Confocal fluorescence microspectroscopy allows us to obtain the fluorescence depth profile of a sample. In this paper, we discuss distribution behavior of fluorescence dye into single porous silica particle using confocal fluorescence spectroscopy. A single silica particle was transferred to the solution including target dye using a micromanipulation/injection system. When the time-dependence of the fluorescence intensity profile of target along the particle central axis is measured, intraparticle diffusion behavior can be evaluated. The fluorescence intensity profile can be simulated using a diffusion coefficient and spherical diffusion model. Moreover, the rate-determining process of intraparticle diffusion on the distribution and release processes can be qualitatively determined as intraparticle and external diffusions from the fluorescence depth profile. The contribution of pore and surface diffusions to the intraparticle diffusion can be estimated using the pore and surface diffusion model. In this account, we introduce the intraparticle diffusion mechanisms of fluorescence dyes, protein (myoglobin), and nucleotides (DNA), mainly focusing on the results of our work.

The Tokoro River Basin is characterized by relatively small discharge amounts that reflect contaminant infiltration to the contaminant concentration more directly than rivers with large discharge amounts. In this study, the population of fecal coliform, an indicator species of fecal contamination level, was modeled using data of water quality and geographical information analysis of the Tokoro River. The contamination load by source differed according to various factors, including the size of utilized land areas, number of rearing livestock according to each dairy farm, and population density of the relevant areas; specifically, the contamination loads were estimated as 8.1 × 10¹⁰–9.8 × 10¹¹ km⁻² year⁻¹, 2.1 × 10¹¹ km⁻² year⁻¹, 1.3 × 10¹²–4.4 × 10¹³ stable⁻¹ year⁻¹, 4.2 × 10¹⁰–1.7 × 10¹³ km⁻² year⁻¹, and 5.4 × 10¹⁰–3.3 × 10¹¹ km⁻² year⁻¹ for the forest and mountain sources, farmland (manure) source, livestock source, urban area source, and human residential areas, respectively. These values were imported to the water exposure analysis model, AIST-Standardized Hydrology-based AssessmeNt tool for chemical Exposure Load (AIST- SHANEL), and the relevant coefficients of determination of the fecal coliform contamination loads were successfully evaluated according to the contamination source.

The shortage and pollution of drinking water are becoming severe problems in many parts of the world. Sanitary water supply is a vital issue for human life. For water disinfection, it is essential to control the concentration of free and combined chlorine appropriately. The authors constructed a flow injection analysis (FIA) system to simultaneously determine free and combined chlorine based on the difference in the photolysis reaction rate. The proposed system contained a Y-branch to separate the injected sample solution into light-irradiated and non-light-irradiated channels. The signals derived from the sample solution, divided into these channels, were detected individually with a time difference, and the simultaneous determination with a single sample injection became available. This study demonstrated the simultaneous determination of hypochlorite ion and chloramine T in the mixture using a pair of simultaneous equations based on pre-prepared relationship curves. The analytical results obtained by the proposed system coincided with the added amount in the mix.

The chemical state of each element is analyzed to understand the reaction mechanism and the deterioration process while developing high-performance materials, such as a lithium-ion battery (LIB) and magnetic material. Several reports demonstrate the application of the X-ray fluorescence (XRF) technique to chemical state analysis; however, the XRF chemical analysis can still be improved further. The author has developed an XRF spectrometer for chemical state analysis in industrial applications. This paper introduces the developed XRF systems in detail, compares it with developed systems and refers to other XRF systems for chemical state analysis. It also reports on the application of the systems to evaluate standard materials and detect the chemical state changes in 3 types of LIB cathode materials. It was confirmed that the XRF spectrometer detected the changes in the oxidation state of 3d-transition metals during the charge and discharge cycles.

A simple analysis method for hypochlorous acid using a test strip and a smartphone has been developed. Hypochlorous acid is a component with a high bactericidal effect among bactericidal agents, however it is not possible to directly measure the colorimetricity of hypochlorous acid with commercially available test papers, and it is necessary to calculate the concentration from the results of colorimetric measurement of pH and total residual chlorine concentration. In this method, we have developed a simple analysis method for hypochlorous acid using a smartphone with original application software. The results show that the proposed method has sufficient sensitivity and accuracy as a simple method. Moreover, because of less susceptibility to interferences in the measurement environment, the hypochlorous acid can be simply quantified by holding the colorimetric plate and the color-plated test paper in front of the camera.

This paper describes a method for rapid water analysis using total reflection X-ray fluorescence (TXRF) analysis. In this method, the dry residues of sample solutions were produced from small volume droplets of the sample solutions in order to reduce the drying time, and TXRF measurements were performed in a short time. In this study, 1 μL droplets of the dry residues of aqueous solution samples were measured for 10 s in air using a portable TXRF spectrometer, and fluorescent X-ray peaks originating from 9 mg L⁻¹ of Cl, 10 mg L⁻¹ of K, 10 mg L⁻¹ of Ca, and 0.3 mg L⁻¹ of Fe in aqueous solution samples were observed. The dry residues of 1 μL droplets of commercially available bottled drinking water were also measured under the same experimental conditions, and the results of these measurements showed that the net intensity of the Ca Kα line linearly increased with the increase in the total water hardness.

In the field of archaeology, there have been reports of a white substance adhering to the inner surface of pottery. According to some reports, X-ray fluorescence analysis, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction performed on the white substance adhered to the inner surface of pottery identified the white substance as a type of aluminum hydroxide crystal. Its origin is not clear. Recently, white adherents were found on the inner surface of Nara-period Sue ware excavated from the Heijo-kyo capital site. We have therefore conducted X-ray fluorescence analysis, FTIR analysis and X-ray diffraction of the white substance on the inner surface of the Sue ware with the aim of elucidating its use, and identified it as bayerite, a type of aluminum hydroxide crystal. It is rare to find bayerite in the identification of the white substance adhering to potteries. The origin of bayerite is thought to be related to the use of the pottery, but there is also the possibility that the external environment was involved. We are working to elucidate the origin of the white substance in light of our previous finding.