BUNSEKI KAGAKU Abstracts

A method of combined microwave-assisted extraction (MAE) and purification using a vacuum manifold was studied on a rapid analysis of persistent organic pollutants (POPs) in soil. Three grams of sample was extracted with mixed solvents composed of 6 mL hexane, 2 mL ethanol, and 2 mL water at 120°C for 30 min. After extraction, the sample was directly applied to the purification process without the performance of concentration and solvent substitution procedures. As a result of a spiked test for POPs, the recoveries of all compounds were over 80%, and the reproducibility of the replicate analysis was within 8.4% of the relative standard deviations. We compared the quantitative determination of POPs in soil by our MAE method and by the conventional Soxhlet extraction method. The concentrations and reproducibility obtained by our MAE method corresponded to those obtained by the conventional method. The total time required for the pretreatment process from extraction to purification procedures was only 2 h.

Self-organization of rationally designed amphiphiles in water based on bottom-up technology selectively gave nanotubes with a well-defined size dimension and functional surfaces. The nanotube channels with 10–100 nm inner diameters formed by monolayer lipid membranes of the amphiphiles were able to act as meso-scale hosts to encapsulate biomacromolecules and nanoparticles. Switching from storage to release for the encapsulated guests was precisely controllable by external stimuli such as pH and temperature. Fluorescence microscopy combined with fluorescence resonance energy transfer (FRET) system enabled us to visualize the transportation of proteins in the nanotube channel. The diffusion coefficient of the protein in the nanotube channel was remarkably smaller than that of free protein in bulk. The endo-sensing procedure also clarified the dependence of the thermal and chemical stabilities of the protein on the inner diameters. The confinement effect, which depends on the size balance between the nanotube inner diameter and the guest proteins, allows the nanotube to stably store those guests while keeping the active state under harsh conditions of temperatures and denaturant concentrations. Furthermore, hierarchal aggregation and entanglement of the nanotubes in water enabled us to develop novel hydrogel inheriting the attractive functions of the liquid-phase nanospace. The nanotube hydrogel was able to stably fix biomacromolecules on glass plates without a tag modification using a covalent bond formation that often induced denaturation of the biomacromolecules. Therefore, the nanotube hydrogel as a soft material will be applicable to bioanalysis.

We have studied on microchip–cyclodextrin electrokinetic chromatography (MC–CDEKC) analysis of enantiomers and microchip–isoelectric focusing (MC–IEF) of proteins by using a commercially available microchip electrophoresis (MCE) instrument equipped with a linear-imaging UV detector, which allows real-time measurements of concentration profiles in a microchannel. In the MC–CDEKC analysis of racemic 1-aminoindane, sulfated-β-cyclodextrin (S-β-CD) was used as a pseudo-stationary phase. Effect of the concentration of S-β-CD on the separation process was investigated. In the MC–IEF analysis of proteins, on the other hand, we studied the processes of a pH gradient formation and protein focusing. Furthermore, effect of the channel length and applied electric field strength on the separation performance of proteins in MC–IEF was studied.

In this work, we analyzed the thermal characteristics of lithium-ion batteries by using an accelerated rate calorimeter (ARC). We conducted a series of thermal characterization experiments on commercial cylindrical lithium-ion cells during the charge-discharge cycle and thermal runaway tests. Thermal profiles during the charge-discharge cycle showed that the rise and drop in the cell temperature depends strongly on the cell chemistry as well as the charge and discharge rates. On the other hand, in the thermal runaway test, cells at different state of charge (SOC) were tested inside the ARC to measure the onset-of-thermal runaway temperatures, and the thermal deterioration was monitored by the impedance (at 1 kHz) and the open circuit voltage (OCV) as a function of the temperatures. An increase in the impedance was observed at around 130°C, corresponding to polyethylene separator shutdown. The separator is micro-porous, and at the melting point (around 130°C), the pores collapse to the form of a relatively non-porous film between the anode and the cathode. The film insulates the ion transport between the anode and the cathode drastically, thereby leading to an increase in the cell impedance. Also, in the thermal runaway test, we found that the thermal profiles of the cells are different for battery materials (electrode, separator). We can thus obtain worthwhile information concerning the thermal and electrochemical characteristics by using the ARC in combination with electrochemical measurements.

A colorimetric method for anionic surfactants by using a digital camera as the detector has been developed. This method is very simple : it involves taking digital photographs of sample solutions after ion-pair extraction of the anionic surfactant with ethyl violet into toluene. In spite of such a simple method, it can accomplish trace analysis, μg/L level, of the anionic surfactant by digital measurements with high precision. Moreover, this method has the following advantages : low cost, experiments on a small amount of organic solvent, and rapid measurements of many samples. This method was applied to the determination of anionic surfactants in river water. The analysis showed good results that were almost in accord with the analytical result of the spectrophotometer.

Many organic compounds, including medicines, have preferred orientation, affected by the sample-preparation methods, which might cause problems in X-ray diffraction (XRD) analysis. To arrive at accurate and correct XRD analysis results of such compounds, we need a specially designed diffractometer, or special techniques to avoid the preferred-orientation effect. X-ray fluorescence (XRF) analysis is liable to cause misunderstandings that it is weak for anlyzing organic compounds, since they are composed in mainly of light elements. The recent progress of synthesized multilayer mirror technology has brought new possibilities in XRD and XRF analyses. The parallel beam method has been widely used in XRD analysis due to its high resolution and sufficiently good brilliance. In XRF analysis, specially designed synthesized multilayer mirrors enable us to carry out low-concentration light elemental analysis such as for boron, carbon, oxygen and so on. In the present work we evaluated the availability of recent progress related to the synthesized multilayer mirror technology in XRD and XRF techniques for organic compounds, including medicines, by performing comparative analyses of acetylsalicylic acid based analgesic antipyretic drugs.

We have developed a determination method for alcohol using high-performance liquid chromatography by using a diamond electrode-electrochemical detector. At this time, 4 alcohols (methanol, ethanol, 2-propanol and 1-butanol) were separated on a Shodex^® ODP2 HP-4E column with an acetonitrile-25 mM disodium hydrogen phosphate buffer (pH 11.0, 1 : 99, v/v) as the mobile phase. The electrochemical detector, equipped with a diamond electrode, was set at 2000 mV (applied voltage). The detection limits of the four alcohols were 20-25 ng/mL. The proposed liquid chromatography was fifty-times more sensitive compared to reported gas chromatography – flame ionization method, and was found to be suitable for large-volume aqueous sample solutions compared to gas chromatography. In the case of poor absorbance compounds, an easy-to-set additional detector in wide using the liquid chromatography – ultraviolet detection system. It was meaningful economical work to use an existing apparatus in the laboratory. With this method, one could determine volatile alcohols, e.g., ethanol, which could not be determined by other universal-type detectors (corona-CAD and ELSD). The proposed method was applied to the alcohol in detergents (contains ethanol and 2-propanol) and alcoholic beverages. Good relationships were obtained compared to the enzymatic method.