The development of experimental techniques for analyzing unknown sample mixtures is an important goal of analytical chemistry. Chromatography has been used as a sample separation method, and spectroscopy has been used as an effective method for identification. Raman spectroscopy has the advantage of providing direct information on molecular structure, but its drawback is weak signal intensity. This type of spectroscopy has not been readily combined (or "hyphenated") with chromatography. The resonance Raman effect and the surface-enhanced Raman effect can be used to increase the signal strength; however, these effects can only be applied when the samples satisfy certain conditions. For this reason, these techniques are not necessarily suitable for the purpose of analyzing unknown samples. Non-resonant Raman spectroscopy has the advantage of being able to detect all molecules. In recent years, several experimental methods have been developed to increase the non-resonance Raman signal strength, making it possible to combine it with LC (LC-Raman measurement). In this review, we introduce methods for strengthening the non-resonance Raman signal and discuss the history of LC-Raman measurements.

This review summarizes the use of attenuated total reflection far-ultraviolet (ATR-FUV) spectroscopy combined with quantum chemical calculations, molecular dynamics simulations, and multivariate analysis to investigate solvation structures and electronic state changes in lithium-ion battery electrolytes. In organic electrolytes, ATR-FUV spectroscopy reveals spectral shifts caused by solvent coordination to lithium ions, showing concentration-dependent structural changes and the formation of contact ion pairs (CIPs) with counter anions at high concentrations. For ionic liquid electrolytes, absorptions from internal excitations of anions and cations, as well as electron transfer between them, are systematically observed and assigned using time-dependent density functional theory (TD-DFT) calculations. This provides detailed insight into electronic interactions within ionic liquids. The electronic influence beyond the first solvation shell is quantitatively evaluated, revealing solvation phenomena not accessible by conventional methods like Raman spectroscopy or NMR. Ions beyond the immediate solvation shell still affect lithium ion electronic states, offering new molecular-level understanding. ATR-FUV spectroscopy enables direct, non-destructive observation of far-ultraviolet electronic transitions in liquid electrolytes under ambient conditions. Its design uses a high-refractive-index prism and evanescent wave probing to overcome atmospheric absorption, allowing stable and reproducible measurements. By integrating ATR-FUV with theoretical and numerical analyses, this approach links molecular solvation structures to electronic properties, essential for designing better electrolytes that improve ion transport and electrode reactions. This integrated method supports the development of next-generation energy storage devices by providing fundamental insights into electrolyte electronic structures and solvation dynamics, both of which are difficult to ascertain using traditional techniques. ATR-FUV spectroscopy combined with computational tools promises to advance electrolyte research and contribute to safer, more efficient lithium-ion batteries.

Raman spectroscopy is a powerful, non-destructive analytical method that can obtain information about molecular composition and structure in situ. In this article, I introduce my recent studies exploring the potential of applying Raman spectroscopy to assisted reproductive technology (ART), focusing on assessing oocyte and embryo quality based on oocyte maturation and embryo culture medium molecular information. In studies of oocyte maturation, Raman spectroscopy successfully detected biochemical changes associated with the post-ovulatory maturation process. Using a 785 nm excitation wavelength, variations in lipid and phosphate concentrations were identified, whereas excitation at 532 nm revealed changes dependent on the redox state of cytochrome c, suggesting the possibility of assessing mitochondrial activity. These findings indicate that the choice of excitation wavelength broadens the range of detectable intracellular biomolecules. The complementary use of different wavelengths enables multifaceted evaluation of biochemical changes, thereby providing detailed molecular information for assessing the fertilization and developmental potential of oocytes and embryos. In parallel, the study investigating human embryo culture media demonstrated that Raman spectroscopy can detect changes in molecular composition and pH within micro drops in a non-contact and label-free manner. This approach represents a breakthrough for evaluating embryo viability and monitoring culture conditions in ART. Importantly, integrating Raman spectroscopy into time-lapse embryo monitoring systems would allow simultaneous molecular and environmental assessment alongside morphological observation, enabling evidence-based evaluation of developmental competence.

In recent years, it has become increasingly important in the field of chiral materials to investigate in detail the chiral optical properties in condensed phases and solids, such as supramolecular assemblies, films, gels, liquid crystals, membranes, polymers, and single crystals, which are attractive and useful reaction fields in chiral induction, chiral amplification, and chiral transfer. However, since representative chiral optical properties such as circular dichroism (CD) and circularly polarized luminescence (CPL) are measured by chiroptical spectrophotometers based on polarization-modulation spectroscopy, caution is required when interpreting the CD and CPL signals of optically anisotropic samples measured by CD and CPL spectroscopy as artifact-free chirality signals. This is because, in the case of CD and CPL measurements of optically anisotropic samples, the coupling signals between non-chiral components derived from linear polarization and polarization characteristics of optical elements are mixed in the measured CD and CPL spectra as false signals. These false signals are troublesome because they are often much larger than the chiral signal. In this paper, we revisit the principles of polarization modulation spectroscopy and provide a comprehensive overview of the methodology for obtaining the correct chiral signal of optically anisotropic samples, as well as the interpretation of the signal using the Stokes-vector-Mueller matrix polarization approach.

There is the journal entitled“Über die Autooxydation von Natriumhypohposphit”published on 1934 ¹⁾. And there is a description in a book²⁾ published on 1965: “when oxygen or ozone was bubbled through the NaPH₂O₂ solution, the products of phosphorous acid, orthophosphoric acid, peroxy acid and others were formed by being accompanied with the rapid absorptions of the gases after 2 or 4 hours of an induction period of the reaction” which seems to be translated into Japanese from the German article¹⁾. However, the reaction mechanisms had not known until when Kimura et al ^3)∼6) reported the complete mechanisms for the peroxodiphosphoric acid formation by the reaction between PH₂O₂⁻ and O₂. The present paper describes not only the meanings of such an auto-catalyzed reaction, but also the possible induced-catalyzers for such a reaction and so on.

A color former was prepared by pretreating cedar sawdust with hydrochloric acid, followed by oxidation with potassium permanganate. The color former reacted with dihydrogen phosphate ions dissociated from NaH₂PO₄ to produce a reddish-brown color (λ_max = 474 nm). In contrast, Na₂HPO₄, KH₂PO₄, and NH₄H₂PO₄ did not produce any significant absorbance in the visible region. The optimum conditions for the spectrophotometric determination of dihydrogen phosphate ions derived from NaH₂PO₄ using the color former were investigated. The optimum conditions for coloration in a reaction volume of 25 mL were the color former amount of 0.1 g, reaction time of 90 minutes, reaction temperature of 25 °C, and pH = 4-6. The color former was used to determine dihydrogen phosphate ions. The calibration curves of dihydrogen phosphate ions were found to be linear over a range of 2.5-25 mmol in the batch method (r = 0.995) and 0.5-4.0 mmol in the column method (r = 0.990). In the presence of phosphate buffer, dihydrogen phosphate ions derived from NaH₂PO₄ could be selectively determined in the range of 5-25 mmol (r = 0.991). Thus, the color former can be used for the selective determination of dihydrogen phosphate ions in phosphate solution.

The silica scale formed by thermal water containing high concentrations of silicic acid (Si(OH)₄) causes problems such as pipe blockage. Because scale formation depends on the components and temperature changes of each thermal water source, understanding the state of silicic acid at each site is important. In this study, we investigated the particle size of polysilicic acid using dynamic light scattering (DLS) and multi-angle dynamic light scattering (MADLS^®) to determine the state of silicic acid in thermal water. In the target thermal water pond, a certain amount of polysilicic acid was already present, and DLS analysis revealed a particle size distribution centered at ∼100 nm. Based on the zeta potential and component concentration, this peak was assigned to polysilicic acid. To obtain more data, the same sample was evaluated using the MADLS^® method. The polysilicic acid peak in a microscopic area was captured, and the particle growth of polysilicic acid was more visible, demonstrating the possibility of using this method to evaluate colloidal particles in hot spring water in the future. The polysilicic acid concentration and the size of the colloidal particles increase with depth in the hot spring pond, and the polysilicic acids react with each other. The formation of coarse particles of ∼500–600 nm was apparent.

In this study, we employed Instrumental Neutron Activation Analysis (INAA) to non-destructively quantify total fluorine (TF) in laboratory apparatus and consumer products. INAA quantifies fluorine by irradiating samples with thermal neutrons to produce ²⁰F, followed by measuring the γ-ray emission (1633 keV) during its decay. This technique allows comprehensive analysis without requiring chemical pretreatment, making it well-suited for complex matrices containing diverse fluorine compounds. To address the challenges posed by the short half-life of ²⁰F and variations in neutron fluence rates, we adopted a cyclic irradiation method, significantly improving the detection limit to 0.2 μg. Additionally, the use of ^46mSc as an internal standard enhanced the reliability and reproducibility of quantitative results. We analyzed 13 laboratory materials and 12 consumer products. High concentrations of fluorine were detected in water-repellent spray-treated papers, certain food packaging materials, and cosmetic products. In contrast, fluorine was not detected in fast-food packaging papers, suggesting differences in fluorine-based treatment practices. Our findings demonstrate that INAA is an effective technique for rapid and comprehensive screening of total fluorine content in diverse products. The combination of INAA-based total fluorine evaluation with LC-MS/MS targeted analysis is expected to establish a more comprehensive analytical framework for product safety assessment and environmental impact evaluation in the future.