Concerning the development of sensing functions of gold nanoparticles were discussed based on conjugation with thermoresponsive polymers. The combination of thermoresponsive polymers and gold nanoparticles enabled us to develop not only their inherent functions, but also new functions that would produce novel analytical systems. Aggregated ca. 13 nm gold nanoparticles conjugated with thermoresponsive polymers were disassembled by thermal stimuli, heating followed by cooling, resulting in a change in the solution color from blue-purple to red. Based on the unique phenomenon, novel analytical methods were developed. On the other hand, gold nanoparticles smaller than ca. 2 nm, referred to gold nanoclusters, exhibited other fascinating behavior. When conjugated with thermoresponsive polymers and heated, the gold nanoclusters grew spontaneously, revealing a reddish color. In addition, when conjugated with sulfhydryl peptides, the gold nanoclusters became fluorescent showing a fluorescence band in the near infra-red region.

The present paper describes a purification method utilizing a combination of conventional Silica gel solid-phase extraction (Si-SPE) and a semi-preparative normal-phase high-performance liquid chromatography (NP-HPLC) for non-esterified long-chain n-fatty acids and sterols extracted from plant tissue. The purpose involves compound-specific isotopic analyses (CSIA) by gas chromatography–isotope ratio mass spectrometry (GC-C-IRMS). The method first separates non-esterified target compounds from esterified ones by using Si-SPE. Then, the obtained polar compounds were further purified by semi-preparative NP-HPLC. An alkaline saponification or interesterification step, which is commonly used for a lipid biomarker preparation method for CSIA, was not employed in the method so as not to “mix” fatty acids, alcohols and sterols of esterified form with their non-esterified counterparts. Applying the method to the extract from raw leaves of Konara oak (Quercus serrate), long-chain n-fatty acids (≥ C₂₆) and phytosterols, including terrestrial higher plant specific biomarker stigmast-5-en-3-β-ol (β-sitosterol) were successfully separated; they achieved “Base-to-Base” separation without any coeluting peaks on both GC-MS (Scan) and GC-C-IRMS chromatograms. The recovery and δ¹³C shift of the target component during the whole pretreatment procedure were 110-125 % and < 1‰, respectively. CSIA of β-sitosterol and long-chain n-fatty acids (C₂₆, ₂₈) extracted and purified from the Konara leaves, sampled in April and October 2018, revealed a slight spring-to-fall ¹³C-depletion of 1.4‰ for both compound classes. This trend resembles the previously reported results for other plant species, and could be ascribed to a seasonal variation of carbon isotopic discrimination in plants photosynthesis.

A method for quantitatively evaluating the factors comcerning the etching process of acrylonitrile-butadiene-styrene copolymer (ABS) resin affecting the adhesion strength of electroless Ni plating on the resin was investigated. The surface of ABS resin dipped in an etching solution (CrO₃/H₂SO₄) for various time periods was analyzed by scanning electron microscopy, scanning probe microscopy (SPM), infrared spectroscopy (IR), and direct analysis in real time-mass spectrometry. The results were analyzed with respect to the adhesion strength. The results suggested that the factors influencing the adhesion strength included the physical factor of adhesion enhancement related to surface roughness, which was found to be correlated to the amount of surface area, as evaluated by SPM. The chemical factor of base material degradation, was found to be correlated to the ratio of the oxide group to styrene (C = O/Ph (Ge)), as evaluated by IR using a Ge prism. In multiple regression analysis, the combined contribution of the two factors was found to be y = −0.022x₁ + 48.99x₂, (correlation R² = 0.67), with y being the predicted adhesion strength, x₁ the surface area, and x₂ the ratio C = O/Ph (Ge). This method can be employed as a simple quantification method for predicting the adhesion strength of between ABS resin and electroless Ni plating.

Optical tweezers can manipulate microparticles, such as bacteria and viruses in solution based on the optical force. Novel optical tweezers for nanoparticles will open a new channel for analytical chemistry. We have developed novel optical nanomanipulation for soft nanomatters with metallic and semiconductor nanostructures. This paper describes such optical manipulation and analytical applications with our technique. First, optical manipulation of thermo-responsive polymer chains in water provides a quantitative analysis to determine the polymer concentration of the phase-separated polymer microdroplet. Second, a localized surface plasmon enables us to enhance the optical force, leading to the formation of micro-assmebly of soft nanomaterials, such as polymer chains and DNA. The polymer micro-assembly can extract organic molecules dossolved in solution for detecting them by means of fluorescence/Raman microspectroscopies. Finally, non-plasmonic nanostructured-semiconductor assisted (NASSCA) optical tweezers will be a powerful tool to trap nanoparticles without any photothermal effect.

This paper introduces our recent research about improving a method for trace element analysis using a portable total-reflection X-ray fluorescence (TXRF) spectrometer. We review our research finding that the TXRF measurement under a low-vacuum condition for reducing the spectral background leads to an improvement in the detection limit of the portable spectrometer. In this paper, a comparison of the TXRF spectra measured in air and under a low-vacuum condition and an example of a spectrum of an analyte containing 2 ng of selenium measured under a low-vacuum condition are shown. A method for the analysis of cyanocobalamin (vitamin B₁₂) at the ng mL⁻¹ (μg L⁻¹) level, which employs a combination of solid-phase extraction for the separation and enrichment of vitamin B₁₂ having a cobalt ion and a measurement of the Co Kα line from the enriched vitamin B₁₂ using this spectrometer, is reviewed. An example of a spectrum of the eluate obtained from a solid-phase extraction column after the solid-phase extraction of a solution of a commercially available tablet containing vitamin B₁₂ is presented. We also show that solid-phase extraction for the separation and enrichment of the analyte element leads to improve the sensitivity for aluminum; we also present an example of a spectrum of the eluate obtained after solid-phase extraction of an infusion of tea containing aluminum. Furthermore, we review our research finding that solid-phase extraction makes it possible to perform trace-element analysis of high-salinity solutions using the portable spectrometer. We also show an example of a spectrum of the eluate obtained after the solid-phase extraction of a high-salinity sample solution containing μg L⁻¹ concentrations of Mn, Fe, Cu, and Zn.

²²²Rn is a radioactive noble gas that occurs naturally in Earth’s crust as an intermediate step in the normal radioactive decay chain of uranium series. A high concentration of radon exposure in air and water causes damage to human cells, therefore the radon concentration in buildings and the diffusive coefficient of shield films have been studied. On the other hand, Radon shows a high solubility for water, and thus a high mobility through groundwater in Earth’s crust. The concentration of radon in crustal fluid and groundwater can provide a clue to understand the state of crustal deformation as crack formation and change in the strain state, because its release rate depends mainly on the rock surface area. The radon concentration in groundwater is usually measured on the sampling site, due to a decrease after sampling by its continuous decay and diffusion to air. To measure the radon concentration at a laboratory, we tried to estimate a diffusion coefficient of the radon for a polyethylene bottle used for keeping water samples in this study. We collected water samples from three hot springs at Sakurajima district in Kagoshima, Japan. We estimated the diffusion coefficient by measuring the radon concentration in the water at different times after several hours of keeping. The estimated diffusion coefficients are 1.6 - 2.4 × 10⁻¹¹ m²s⁻¹ (averaged: 1.9 × 10⁻¹¹ m²s⁻¹). The values are similar to those from an experiment using polyethylene films, suggesting that the diffusion coefficient obtained in this study is reasonable. Concerning the error on the estimated diffusion coefficient obtained here, we used maximum residual value range of the estimated value, 20 %, because the residual error on the estimated values was larger than that on the measurement.

It has become clear that 1,4-dioxane exists not only as a contaminant in aquariums, but also in the atmosphere at a constant concentration. It has been reported that 1,4-dioxane is produced from the highly reactive lime in bag filters from industrial waste incineration treatment facilities; however, the source of the 1,4-dioxane that is released to the atmosphere is primarily surfactant manufacturing plants. In this study, in order to clarify the mechanism of 1,4-dioxane formation in a bag filter coated with highly reactive lime, and to accurately evaluate the amount of 1,4-dioxane produced from a certain amount of this highly reactive lime, headspace-GC/MS was explored as an analytical method. The formation of 1,4-dioxane in the bag filter was successfully reproduced. In addition, the amount of 1,4-dioxane produced for 2.0–40 μg g⁻¹ of lime was found. Also, Headspace-GC/MS was found to be the only evaluation method that could be used to study highly reactive lime without generating 1,4-dioxane. Further, it is an excellent method for confirmation when selecting highly reactive lime for use in industrial-waste incineration treatment facilities.