BUNSEKI KAGAKU Abstracts

Radio frequency glow discharge (rf-GD) is being used as a luminous optical device for the analysis of thin-film samples. A depth analysis and an element analysis are purposes. The Ar^＋ ions that occur in the rf-GD provide irradiation energy (＜50 eV) and ion electric current (〜100 mA/cm²). As for the Ar^＋ ion by rf-GD, damage to the sample is less than the detection lower limit of the main way of detecting it. Then, an influence on the material is minimum. On the other hand, it has a unique nature of high-speed Ar^＋-ion sputtering. Observations at a in the low acceleration voltage of 1〜1.5 kV are possible recently with a scanning electron microscope (SEM) by loading feild emission gun. The SEM detection signal (the secondary electron, backscattered electron) of the acceleration voltage (1〜1.5 kV) is a sample surface number atom. The treatment is being requested to be made in front of the surface of a rapid sample where damage dose not occur. The treatment can improve the image of SEM remarkably before the sample for which rf-GD was used. Then, we can obtain much information about the material. Furthermore, it can be applied to focus ion beam (FIB) to a transmission electron microscope (TEM) sample preparation process. Rf-GD is the most effective means to solve polluted layer removal by Ga^＋ ion which is the subject of FIB.

We developed a molecular-recognition material of low-molecular-weight organic compounds by using mesoporous silicas, and applied this material to a chemical sensor, aiming at the development of new and practical analytical techniques. We have found that it is important to determine the optimized surface condition and the porosity of mesoporous silicas to compare very similar molecules, namely benzene and toluene, which have no and one methyl group, respectively, in their molecular structures. We applied mesoporous silica to a micro gas-sensing system, which has been originally developed. We succeeded to detect benzene gas at ppm levels in car exhausts containing interference components. We also found that mesoporpos silica is an excellent optical material in the terahertz region, and we developed a useful way for terahertz time- domain spectroscopy to distinguish between intra- and intermolecular modes by incorporating target molecules in nano-sized spaces of nanoporous materials.

Microwave-assisted extraction (MAE) was applied to the extraction of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin, like polychlorinated biphenyls (DL-PCBs) in soils and sediments. The samples were extracted by MAE with solvents composed of hexane, water and ethanol at a temperature of 125°C for 30 min. The optimized extraction conditions were as follows : hexane (1 mL), water (0.3〜0.5 mL) and ethanol (0.8 mL) for 1 g of an experimental sample. The concentrations of PCDD/DFs and DL-PCBs were equivalent to the results obtained by the conventional method using Soxhlet extraction, and the reproducibility of MAE was below 20％ in experiments with four samples of soils and sediment. In addition, our extraction method could drastically reduce the extraction time and facilitate a reduction in organic solvent consumption, compared with the conventional method using Soxhlet extraction.

A cyclic flow injection analysis is proposed for the determination of acidity (expressed as citric acid content) in fruit juices and soft drinks. The method is based on acid-base neutralization for detecting the color change of a pH indicator. A reagent carrier solution consisting of 1.5×10⁻⁴ M Xylenol Orange (XO) and 12％ (w/v) sucrose in 0.01 M phosphate buffer (pH 8.0) was continuously circulated in a single-line cyclic flow system. Into the stream, a 5 μL sample solution was injected, and the color change of XO was monitored spectrophotometrically at 400 nm. Sucrose is added to the reagent carrier solution in order to compensate both the differences in the refractive index and the viscosity between the carrier and the sample solutions, which make the sample injection direct without any dilution process. Several parameters were optimized, resulting in a simple, fast, effective and economical acidity monitor. The procedure has been applied to determine acidity in fruit juices and soft drinks.

Metallic glasses containing iron, cobalt, niobium, boron and silicon were analyzed. The samples could be dissolved only with a mixture of hydrofluoric acid and nitric acid. After a sample dissolved, metallic elements were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Conventional ICP-OES instruments were not employed because hydrofluoric acid attacked the plasma torch, chamber and nebulizer, which were made of quartz or glass. When a sample solution contained hydrofluoric acid, hydrofluoric acid was removed by heating with sulfuric acid. However, this removal technique led to a loss of boron and silicon. By a microwave-assisted dissolution procedure with a mixture of hydrofluoric acid and nitric acid, boron and silicon were not vaporized. A hydrofluoric acid resisting ICP-OES instrument was employed for elemental determination. The total values of all the elements determined were almost 100％.

The Japan Society for Analytical Chemistry carried out proficiency testing on the determination of hazardous elements (lead, cadmium, chromium, mercury and bromine) in polyester disks or chips four times from 2003 to 2007. The number of laboratories that participated was 140 at the most (2nd) and 104 at the least (4th). The analytical methods applied in the testing were chemical analysis and X-ray fluorescence analysis. The concentration levels of the analytes were both low and high ; at low concentration, it was about 1 μg g⁻¹ for Hg and 5〜10 μg g⁻¹ for other elements, and about 10-times at a high concentration in 1st PT. In 2nd〜4th PT, it was 20〜30 μg/g⁻¹ level for each element at low concentration, and 2〜3 times at high concentration. More than 80％ of the laboratories obtained z score of less than 2 in absolute value, which represents “satisfactory”. The uncertainties were generally larger in X-ray fluorescence analyses than in chemical analyses. However, it was reverse in the case of Br. This would have been caused by incomplete chemical decomposition of the samples. From an estimation of the correlation of the analytical results between two analytical methods using the En number, some points were shown to be improved in the practice of X-ray fluorescence analysis, such as in selecting kinds of reference materials, or in a matrices correction of the sample.

Stir bar sorptive extraction (SBSE) is a sample preparation technique that involves the extraction and enrichment of organic compounds from a liquid sample. The present study focused on the determination and assessment of phenolic xenoestrogens exposure. Firstly, the determination of octylphenol (OP), nonylphenol (NP) and bisphenol A (BPA) in river water samples by SBSE and thermal desorption (TD)/gas chromatography mass spectrometry (GC/MS) was developed. The limits of detection (LODs) of OP and NP were 2 and 20 ng L⁻¹, respectively. On the other hand, the LOD of BPA was 0.5 μg L⁻¹. Secondly, a simultaneous analysis of phenolic xenoestrogens, such as OP, NP, BPA, dichlorophenol (DCP), butylphenol (BP) and pentachlorophenol (PCP) in river water samples by SBSE with in situ derivatization and thermal desorption (TD)/gas chromatography mass spectrometry (GC/MS) was developed. The LODs of phenolic xenoestrogens in water samples were 0.5〜5 ng L⁻¹. A highly sensitive analysis was achieved by using SBSE with in situ derivatization method. Thirdly, the SBSE with in situ derivatization method was applied to measure phenolic xenoestrogens in human urine sample. The LODs of phenolic xenoestrogens in human urine samples were 0.01〜0.05 ng mL⁻¹. In addition, the quantity of phenolic xenoestrogens in human urine samples was obtained. Exposure assessments of phenolic xenoestrogens could be performed.