BUNSEKI KAGAKU Abstracts

Gold nanorods (AuNRs), which are rod-shaped gold nanoparticles, exhibit unique localized surface plasmon resonance (LSPR) on the basis of their anisotropic shape. Particularly, the longitudinal mode of LSPR, based on the oscillation of free electrons, appears in the near infra-red region, and generates much stronger electric fields as compared to spherical nanoparticles. In addition, it exhibits a larger peak shift, depending on the refractive indices of the surrounding medium, as compared with the case of spherical nanoparticles. Furthermore, the anisotropic shape leads to drastic changes in the optical properties of AuNRs, depending on their agglomeration (organization) conditions. Accordingly, AuNRs are expected to be promising in various fields, such as polarized filters, photoenergy conversion systems, sensors, and so on. In this paper, resent research results on AuNRs carried out in our group will be summarized from the viewpoints of analytical science.

Ionic liquids (ILs) with protonated cations were investigated as extraction solvents for gold(III) (5 × 10⁻⁷ to 6 × 10⁻⁴ mol dm⁻³) in hydrochloric acid (0.1 to 4 mol dm⁻³) at 25°C. The protic ILs used were salts of bis(trifluoromethanesulfonyl)amide ([NTf₂]⁻) with 1-butylimidazolium ([BImH]⁺), 1-butylpyrrolidinium ([BPyrH]⁺), and trioctylammonium ([TOAH]⁺). The extractability of gold(III) increases with decreasing hydrochloric acid concentration and with increasing gold(III) concentration. The gold(III) extracting ability of the ILs follows the sequence [TOAH][NTf₂] > [BImH][NTf₂] > [BPyrH][NTf₂]. Almost quantitative extraction is possible from a 0.10 mol dm⁻³ hydrochloric acid solution with a 1/10 volume of [TOAH][NTf₂]. From equilibrium analysis, it is suggested that gold(III) is extracted as electrically neutral species, [AuCl₃] and [Au₂Cl₆]. The equilibrium constants for the reactions [AuCl₄]⁻_(W)⇄[AuCl₃]_(IL)+Cl⁻_(W) and 2[AuCl₃]_(IL)⇄[Au₂Cl₆]_(IL) (W: aqueous phase, IL: IL phase) are determined. The dimerization constant of [AuCl₃] is largest in [TOAH][NTf₂], which is a main cause for the highest extracting ability of the IL.

Biofilm is generally formed on various industrial materials by bacteria; the attachment process of bacteria onto materials and following interfacial phenomena are called biofouling. Biofilm causes beneficial and detrimental effects to the materials. In this paper, we first explain the interaction between biofilm and the materials. We then mention some problems concerning industrial materials caused by biofilm, and biofouling from the viewpoint of the interactions between biofilm and materials. We then cite some biological analyses, and clarify how different the analysis for planktonic bacteria is from that for biofilm bacteria. Finally, we mention our unique approaches to analyze biofilm and biofouling from the viewpoint of materials science and engineering. The paper is composed of the following points: 1, Introduction; 2, biofilm formation and metal elements; 3, various problems concerning materials science and engineering caused by biofilm; 4, biofilm analyses from the viewpoint of biology; 5, visualization analyses from the viewpoint of materials science and engineering; 6, conclusions.

Titanium and titanium alloys are used in industries and consumer products, as well as is a wide range of products. On the other hand, the toxicity of titanium is a serious concern. Knowledge about the chemical state and behavior of titanium ion in a solution is lacking. We thus investigated this information, the reaction system and the structure in the solution based on the results of monitoring using electrospray ionization mass spectrometry (ESI-MS), and compared with it other methods. After analyzing titanium trichloride (TiCl₃) and titanium tetrachloride (TiCl₄) by ESI-MS, the hydrolyzed species of the titanium ion was confirmed, and the existence of the monomer and the polymer were consistent with results by other methods. In addition, the natural oxidation of Ti³⁺ and oxidation with an oxidizing agent were analyzed using ESI-MS and inductive coupling plasma atomic emission spectrometry (ICP-AES). It was confirmed that Ti³⁺ was oxidized to Ti⁴⁺ in the solution, and that Ti⁴⁺ caused gradual precipitation. To increase the reaction rate, an oxidizing agent was added to TiCl₃, and some polymers of Ti⁴⁺ could be examined. In this study, the identification of dissolution species, as well as the oxidation and hydrolysis processes of Ti with ESI-MS were well elucidated.

Carbonate skeletons of precious corals, other corals and a giant clam were analysed by synchrotron radiation-infrared spectroscopy (SR-IR) at beam line BL43IR, JASRI (SPring-8) to establish necessary basic technologies for the sustainable use and control of the trade of precious corals. Precious and bamboo corals differed from hump and stylasterina corals and giant clam in microspectroscopic spectra of the axes. The spectra of the former showed a particular type of calcite, whereas the later spectra indicated an aragonite. The spectrum of a deep-sea coral collected from off Midway Is. is different from that of other precious corals. Also that of a deep-sea coral collected from off Ogasawara Is., Japan was different from other corals in the spectra of sclerites. As a result of synchrotron infrared mapping analysis in the cross-section of precious coral axis, changes in the absorbance were observed at some wavenumbers. The cycle of fluctuation ranged from 109.23 to 147.17 μm. The fluctuation was considered to be an annual change. Therefore, the radial growth rate of precious coral axis was estimated to 0.22 – 0.35 mm year⁻¹. This study indicates that synchrotron radiation-infrared spectroscopy analysis is effective to differentiate a genuine from a fake precious coral and to estimate the growth rates of precious corals.

A zero-emission flow injection analysis (FIA) system with an immobilized peroxidase enzyme reactor column (POD-IE) used for the determination of a micro amount of hydrogen peroxide has been developed. A FIA system composed of multiple flow channels was reconstructed to be a mono flow channel; the HPPA dimer generated by the reaction among hydrogen peroxide, horseradish peroxidase and 3-(p-hydroxyphenyl)-propionic acid (HPPA) was utilized as a fluorometric indicator. After measuring the fluorescence intensity of the HPPA dimmer, the flow stream passes through an anion exchange resin column (packed Waters: sep-pak Accell plus QMA). The HPPA dimer and only non-reacted HPPA reagent are removed, and the stream is circulated. A solution containing hydrogen peroxide was injected into the FIA system in previous work. In the present work, it was injected into a solution mixing HPPA and a sample solution containing hydrogen peroxide, for such a purpose as reducing the amounts of reagents used. The correlation coefficient of the FIA system was more than 0.998 in the linear range of the calibration curve (0 to 0.070 ppm). The relative standard deviation at 0.040 ppm of hydrogen peroxide was 6.86% (n = 7). After only effects of coexisting substances and ions thought to be contained in rain-water were examined, it was applied to the determination of hydrogen peroxide in the rain-water as practical samples.

Decay ratios of the laser-induced fluorescence emitted from five types of asbestos (chrysotile, crocidolite, amosite, tremolite, and anthophyllite) and six types of building materials (glass wool, rock wool, rock fiber, talc, plaster, and cement) in the broad wavelength region from 350 to 650 nm were investigated by using an ultraviolet laser pulse of 266 nm. The dependences of the decay ratios on the wavelength were compared, and evaluated in an attempt to numerically discriminate asbestos from other building materials. It was observed that the decay ratios of each material were not constant over the wavelength region, but varied in the wavelength over time. There were significant differences in the decay ratio between asbestos and fibrous building materials in the wavelength region from 360 to 400 nm. The wavelength region of 405 – 407 nm was found to be optimum in order to identify types of asbestos and to discriminate asbestos from the building materials by comparing the decay ratio at a delay time of 10 ns after the incidence of a laser pulse.

We determined the stable carbon and nitrogen isotopic compositions (δ¹³C and δ¹⁵N) and nine trace element abundances (Mg, P, Ca, V, Mn, Zn, Rb, Sr, and Ba) of boiled and salted wakame (Undaria pinnatifida) from Sanriku, Naruto, South Korea and China, in order to evaluate their interannual variations between 2011 and 2012. The wakame from Naruto was characterized by relatively higher δ¹⁵N values than those from other areas in both years. There was no significant interannual variation of the δ¹³C and δ¹⁵N values. Based on a linear discriminant analysis using the δ¹³C and δ¹⁵N values of wakame collected in 2011, 93.0% of Naruko wakame could be distinguished from all others in 2012. Although the wakame from China had relatively higher abundances of Mg, V, Mn, Ba in both years, there were interannual variations in the abundances of Mg, V, P, Ca and Rb. Based on these δ¹³C and δ¹⁵N values and the trace-element abundances (Mg, V, Mn, Zn, and Ba) of wakame collected in 2011, we divided the wakame collected in 2012 into three groups: Naruto, China, and other areas (Sanriku and South Korea), with 98.2% and 83.3% discriminations being achieved for Naruto and China, respectively. The discrimination rate of wakame from China in 2012 decreased because of the interannual variation in the abundances of the trace elements. Thus, the interannual variation of the stable isotope and the trace-element compositions is needed to establish their database in order to discriminate the geographical origin of boiled and salted wakame.

Sr isotope ratio and trace elements (Al, Ti, Mn, Fe, Ni, Cu, Zn, Rb, Sr) of 52 paprika samples (from Japan, Korea, New Zealand and Netherlands) were measured using inductively coupled plasma mass spectrometers of the double-focusing type and the quadrupole type, respectively. The relative standard deviation of the strontium isotope ratio (⁸⁷Sr/⁸⁶Sr) for a NIST SRM 987 standard was as small as 0.033% by optimizing the measurement conditions of the device. The obtained data were statistically evaluated so as to investigate whether there was a significant difference between domestic and foreign products cultivated by nourishing solutions. Although domestic products were limited to two cultivated areas, a linear discriminant analysis (LDA) model allowed the discrimination of domestic and foreign products with high (domestic products) accuracy. Consequently, the present study has demonstrated that the production place of paprika cultivated by a nourishing solution can be estimated by the ⁸⁷Sr/⁸⁶Sr isotope ratio and the Sr concentrations.