BUNSEKI KAGAKU Abstracts

Ultrapure water is used in various areas such as pharmaceutical manufacturing, electric power generation, and the electronic industry. The types of noticeable impurities and required purity vary, too. Especially, purity for ultrapure water used in the semiconductor sector is so demanding as to be required to remove almost all impurities to the utmost limit. To evaluate the water quality of such ultrapure water, the sensitivity of online measuring equipment is not enough, and off-line analysis using more sensitive analysis equipment is necessary. Preconcentration techniques to increase the sensitivity and various contamination controls including from sampling to analysis are necessary in off-line analysis. Examples of measuring metal components and nonmetal components in ultrapure water for semiconductor at the ng L⁻¹ to pg L⁻¹ level by using these water-quality evaluation techniques are introduced.

The performance of a solar-powered small automatic rainwater collector was investigated, which was developed with an emphasis on small-size, lightweight, and inexpensive for use in a wet deposition monitoring network in a mountainous area. It was studied at Tarobo, which is located at the southeast mountainside (1300 m a.s.l.) on Mt. Fuji, during four years from July 2005 to September 2009. The rainfall amounts estimated by the automatic rainwater collector corresponded to those observed by a rain gauge verified by Japan Meteorological Agency. A comparison of the rainwater chemistry by the automatic rainwater collector with that by a commercially available wet-only sampler indicates that the automatic rainwater collector is available for use in wet deposition monitoring in mountainous areas. The mean annual wet deposition fluxes of H^＋, NH₄^＋, NO₃⁻, and SO₄²⁻ at Tarobo were 48.9, 35.0, 38.0 and 69.4 meq/m²/y during three years from 2006 to 2008, respectively, and were higher than those at remote sites in Japan, particularly NO₃⁻ deposition. The concentration of acidic substances at Tarobo was nearly equal to those at remote sites in Japan, so it is expected for Tarobo to be in use for a remote site of an acid-deposition monitoring network in Japan because of easy access to Tarobo.

In recent years, along with the development of metallomics and nanotechnology, the focus target of elemental analysis has been shifted to smaller samples, such as bio cells and nano-particles. Argon-inductively coupled plasma (Ar-ICP) is widely used as an ionization or excitation source for elemental analysis, because of the analytical figures of merit. However, the conventional ICP system consumes a relatively large volume (typically 1 mL min⁻¹) of sample solutions, and thus is not suitable for the analysis of smaller amounts of samples. Additionally, the determination of a higher ionization potential element, such as halogens, was difficult. In order to overcome these problems, a new sample-introduction system and a new plasma sources have been developed by our group. In this paper, we report an three original devices : (i) a droplet direct injection nebulizer (D-DIN) system in which aqueous solutions are not nebulized, but directly injected into the plasma with just a single droplet or a series of small droplets ; (ii) a multi-gas ICP which can sustain Ar, N₂, CO₂, O₂, He and air plasma at atmospheric pressure ; and (iii) a multi-gas microplasma source that can generate a high-density and high-temperature plasma under atmospheric pressure using various gases.

From the standpoint of polymer process applications based on near-infrared (NIR) spectroscopy and chemometrics, robust calibration models have been requested. Moreover, it has been expected to develop precise calibration models using sample data and spectra with small size because of savings in costs and labor. The purpose of the present paper is to describe some solutions for the above problems. An on-line monitoring system for molten polymers based on a Fourier-transform near-infrared (FT-NIR) spectrometer was developed. The influences of a change in the optical fiber temperature and sample temperature have been investigated. Furthermore, a modified multiplicative scatter correction was proposed as a traceable compensation method for changing the effective pathlength by a change of the sample temperature. NIR spectra of linear low-density polyethylene (LLDEP), random polypropylene (RPP), block polypropylene (BPP), and ethylene vinyl acetate copolymer (EVA) in the melt and solid-states were measured by the on-line and laboratory FT-NIR system, and compared in detail. The sample sets for developing prediction models for the density of LLDPE were collected for three months at a plant, and the density of LLDPE was continuously monitored on-line for another three months using the calibration model. A prediction of the ethylene content in the melt states RPP and BPP was studied. The method using a difference spectrum between a RPP and a BPP spectrum has been proposed to transfer from the BPP calibration set to the RPP calibration set. The calibration models for the vinylacetate (VA) concentration in EVA copolymers has been investigated and proposed to make use of band shifts associated with concentration changes in the VA for improving of the models. Finally, a practical calibration correction method for an on-line monitoring system has been studied. It has been demonstrated that the proposed method, considering the wavenumber shift and path-length correction, is useful for a calibration correction in a real plant.

Seven types of vegetable oils and two types of processed oils, which have been widely on sale, were analyzed and identified by liquid chromatography/mass spectrometry (LC/MS). The main constituents, triacylglycerols (TAG), could be rapidly detected using a non-aqueous reversed-phase mode. The characteristic mass spectra which reflected the TAG chemical structure were observed for each oil. Since the sample materials in a forensic examination are mostly unknown, this observation can be powerful evidence to identify an unknown sample as a TAG mixture, that is, fats and oils. Furthermore, each chromatogram pattern clearly reflected its own TAG composition and could be used to discriminate their oils. This phenomenon was also applied to processed oils. The oil including medium-chain fatty acids gave additional peaks on chromatogram compared with those of other vegetable oils. These peaks were derived from additional TAG including medium-chain fatty acids as components. The oil mainly constituted from diacylglycerols (DAG) also gave additional peaks which were derived from DAG themselves. These results indicated that LC analysis may be useful for the analysis of even processed oils. LC/MS analysis of vegetable oil easily gives information concerning the oil’s nature without any pretreatment. Therefore, this analysis may be a powerful one for investigations and discriminations of oils in forensic examinations.

Coumarin in sulfuric acid-pitch/alkali-sludge was determined by GC/MS after an acidified liquid-liquid extraction of alkaline sample extracts. Shading at alkali extraction brought about a good result, and this was probably due to the prevention of UV-rays, which isomerize coumarin in an alkaline solution to trans-o-hydroxycinnamate anion. Outdoor samples of alkali-sludge and sulfuric acid-pitch contained 0.16〜0.43 mg/kg and 51〜72 mg/kg of coumarin, respectively ; and these samples were thought to be derived from production of illegal gas oil.

In Japan the permitted maximum concentration of cadmium in whole-rice is regulated by the standard of the Food Sanitation Act. A typical method for the quantitative analysis of cadmium in whole-rice includes complicated and troublesome sample-preparation procedure. We propose to use an inductively coupled plasma atomic emission spectrometer connected to a double-chamber electro thermal vaporization (ETV) system to measure cadmium. This technique does not require any chemical preparation. A calibration curve to determine the cadmium concentration obtained by the ETV method has been made using the certification standard of Rice Flour (NIES No. 10). The obtained results of the cadmium concentration were compared with the value obtained by the wet decomposition method. A good correlation between the results has been shown. The ETV method could be used as a quick analytical way to measure the cadmium concentration in whole-rice within 3 minutes without any chemical sample preparation.