BUNSEKI KAGAKU Abstracts

The optimization of the analysis of volatile organic compounds in atmospheric water samples, such as rainwater and dew water by head space solid-phase microextraction and gas chromatography/mass spectrometry (HS SPME/GC/MS), was studied. The sensitivity of 23 VOCs, i.e. halogenated hydrocarbons and monocyclic aromatic hydrocarbons, was the highest after the extraction of VOCs in 16 mL of samples including 3.5 g of sodium chloride to SPME fiber (100 μm PDMS) at 40°C during 20 min of incubation. The repeatability of 1 ppb VOCs standard solution was below 10%, except for 1,2-dichloroethane (13%), and their detection limits ranged from 0.02 nM for dichloromethane to 0.30 nM for benzene. The recoveries of 22 VOCs, except for dichloromethane, ranged from 80 to 120% under the condition where 32 μL of 0.5 ppm VOC standard solution and 5 ppm fluorobenzene as an internal standard was added to 16 mL of atmospheric water samples. The application of the HS SPME/GC/MS method to the determination of VOCs in rainwater and dew water, which was collected in the western part of Tokyo, Hino, revealed that 6 chlorinated hydrocarbons (CHs) and five monocyclic hydrocarbons (MAHs) were detected, and the concentrations of MAHs were higher than those of CHs. Toluene was the dominant VOCs both in rainwater and dew water in Hino, and the volume-weighted concentrations of toluene in rainwater and dew water were 3.31 nM (n = 39) and 5.21 nM (n = 38), respectively. The results of this study made clear that the observed concentrations of VOCs in rainwater and dew water were considerably higher than the estimated concentrations, which were based on Henry’s law equilibrium.

Along with the shrinkage of LSI geometries, a higher quality of ultrapure water has been continuously required. Analytical technology for ultrapure water has also progressed before ultrapure water production technology improvements. In this study, we performed optimization of the analytical conditions for the direct analysis of acid droplets, and established an analytical technology for measurements of trace amounts of metallic impurities deposited on a wafer surface by means of Vapor Phase Decomposition (VPD)/Inductively Coupled Plasma Mass Spectrometry (ICP-MS). As a result, analytical technology for metallic elements of the 1 × 10⁸ atoms/cm² level on wafer surface has been established. By applying analytical technology to the wafer that has been contacted with ultrapure water, a new evaluation technology for ultrapure water quality by means of wafer surface contamination has been established. We confirmed good correlations between metal contamination of the wafer surface and the concentration in ultrapure water. This new quality evaluation technology is expected to contribute a further improvement of ultrapure water for future LSI manufacturing.

A quality test for water purification of TiO₂-photocatalyst coated materials (photocatalytic materials) has been observed using ion-exclusion chromatographic methods. Ion-exclusion chromatography has been used to decrease the carboxylate ion and the formation of its products in photooxidation process of a carboxylic acid, e.g., propionic or butyric acids, on the time-dependency of UV irradiation. Ion-exclusion/cation-exchange chromatography has been used to determine relationships between the decrease of an aliphatic amine and the formation of ammonium and nitrate ions. In a quality test standardized in Japan, dimethylsulfoxide (DMSO) was adopted as the starting sample because of stoichiometric oxidation with an OH radical generated from TiO₂. A fundamental study on the photodegradation of DMSO was provided by ion-exclusion/adsorption chromatography. Also, in this paper, ion-exclusion chromatographic methods with post-column reactions are described for the detections of aliphatic carboxylate, carbonate, phosphate, and silicate ions in quality tests for photocatalytic materials.

In order to respond to the Japanese positive list system for residual agricultural chemicals in salt products, 116 agricultural chemicals were selected. For a scientific certification of safety compliance, an analytical method for all 116 residual agricultural chemicals in salt should be developed. In the present study, a simultaneous determination method for agricultural chemicals in salt by gas chromatography/mass spectrometry (GC/MS) was examined. Mixtures of agricultural chemicals were added to salt samples, and they were extracted by solid phase extraction (SPE). Among four SPE sorbents examined, a styrene-divinylbenzene copolymer (PS-2) column showed the best performance, where 94 agricultural chemicals could be successfully extracted. By the improved method with PS-2 column, 94 agricultural chemicals could be successfully detected with the recoveries higher than 70%, and relative standard deviations within 20%. Detection limits of targeted chemicals were less than 0.01 mg/kg.

Cadmium(II) ion has been sensitively determined with water-soluble porphyrin by spectrophotometry. However, the conventional method required a removal procedure for zinc and lead before an analysis of cadmium. Some kinds of pretreatments for the removal of interference ions, which was a solvent-extraction or co-precipitation procedure, were complicated. Therefore, a simple and easy removal method for lead and zinc interference has been investigated. The interference of zinc was avoided by using a large amount of zinc as a metal component for an indicator reaction between Zn and TPPS. As the result of a search on some removal procedures, we have found that a masking agent is effective for the removal of lead interfere. Lead (II) was masked with Bis-Tris using as a Good pH buffer reagent. This method was a batch procedure by controlling the reaction time, temperature, light and others. The optimum conditions by the present method were as follows : sample solution 70 mL ; TPPS (3.0 × 10⁻⁶ mol/L); Bis-Tris (10⁻² mol/L); Zn, 4 ppm ; pH, 8.0 ; temperature, 25°C ; reaction time, 5 min ; and measurement wavelength 422.5 nm. The calibration curve was liner over the range of 0 to 100 ppb. The determination limit of cadmium was 1.6 ppb. The RSD of 10 ppb cadmium was 1.4%. Zinc(II) and lead (II) were tolerated up to 2 ppm and 0.5 ppm. The proposed method was applied to the determination of a soil standard sample.

Halogeno derivatives of 2-aminobenzenethiol (ABT), 4-chloro-2-aminobenzenethiol (4-ClABT), 5-chloro-2-aminobenzenethiol (5-ClABT) and 4-bromo-2-aminobenzenethiol (4-BrABT) react with platinum(II) ion in aqueous Triton X-100 micellar solutions to form stable near-IR absorbing 1 : 2 complexes with a molar absorptivity, ε, of 7 to 8 × 10⁴ M⁻¹ cm⁻¹, in the presence of iodine (1.0 × 10⁻⁴ M). As compared with the platinum(II)-ABT complex (ε = 5.8 × 10⁴ M⁻¹ cm⁻¹ at 735 nm), the absorption maxima (λ_max) of these ABT derivative complexes shift to longer wavelengths with increased molar absorptivities ; the platinum(II)-4-BrABT complex has a value of ε = 7.5 × 10⁴ M⁻¹ cm⁻¹ at 759 nm. Consequently, the introduction of electron-withdrawing groups to the 4th position of the ABT ligand as near-IR colorimetric reagents is of great advantage to the trace analysis of platinum(II) ion.

With the growing demand for less uncertainty in the determination of oxygen in steel, an alternative reference material has been investigated. Among the several pure substances we experimented on using an infrared method after fusion under an inert gas, potassium dichromate, when being dropped into a tin bath of 1 g at a temperature of 2300°C, was completely decomposed and showed an oxygen analysis value that conformed with the theoretical value with a good repeatability standard deviation (σ < 2 μg/g) and good linearity (R² = 0.9997) to 500 μg/g in the calibration curve. A suitable amount of tin bath is needed when using potassium dichromate, because the oxygen that it contains cannot be completely extracted without a tin bath. These results show that potassium dichromate is applicable for calibration. The oxygen analysis results of other pure substances didn’t conform with the theoretical values. To identify the causes of the discrepancy, we further analyzed, using FT-IR, the composition of evolved gases generated at the impulse furnace. Carbon dioxide and hydrocarbon gases were detected in addition to carbon monoxide. We also found from the infrared absorption spectrum that potassium hydrogen phthalate contained water of crystallization when being dried. These are considered to be the causes that make the oxygen analysis results higher than the theoretical values.

Recently, progress in molecular biology is being made in the fields of science, medicine, and pharmacy. Therefore, the majority of students graduating from pharmaceutical university departments will be required to have knowledge of molecular biology techniques. However, it is difficult to include such experiments in the curriculum for students at general high schools and universities because of safety concerns, the expensive materials and experimental equipment and time consumed. Therefore, this report introduces the convenient experimental materials on human DNA polymorphism for the genotyping of the earwax type gene ABCC11 on the chromosome 16 using a PCR-RFLP method. This experiment enables each student to handle DNA safely. The total time required for the experiments is less than 4 hours. The PCR-RFLP experiment proposed here is a suitable genotyping method to acquire molecular biological knowledge and techniques.

Head space (HS) extraction is known as a sample-preparation method of gas chromatography (GC) for volatile organic compounds (VOCs). It is classified into a static HS method and dynamic HS method, such as the purge-and-trap method. Though the purge-and-trap method accelerates sample evaporation, it has drawbacks, such as a poor reproducibility and a need for large equipment. The static HS method is based on the vapor-liquid equilibrium. Though the static HS method is very easy to perform, it takes a long time to attain an equilibrium state. In this work, a compact and rapid vapor-liquid equilibrium system was developed. To attain the acceleration of vapor-liquid equilibrium, an ink-jet was used to generate ultra-small sample liquid droplets. The ink-jet is a well-known technology for printers. It can eject many small liquid droplets in a short time with good reproducibility, and it is expected to increase the area of the vapor-liquid interface of unit volume of the liquid. An ink-jet microchip was fitted on the cap of an extraction vial with epoxy glue. The proposed system with the ink-jet was compared with the conventional static HS method by applying it to the extraction of VOCs in water. The vapor-liquid equilibrium for both methods was evaluated by ECD-GC with the peak area. The results showed that the proposed method accelerated the vapor-liquid equilibrium. The length of the vial was effective in reproducibility. When the length was changed from 80 mm to 98 mm, RSDs were improved from 3.2∼22% to 3.0∼14%. Considering the flight time of the droplet from ejection to touchdown to the bottom of vial, and the diffusion time of the target ingredients, the vaporizing efficiency would be thought to depend on the droplet flight time. The proposed system showed good linearity for 0.01∼1 ppm VOCs in a short equilibrium time. The regression coefficients for an extraction time of 0 min were 0.992∼0.999. It was applied to tap water and wastewater, then demonstrated to be useful for the detection of VOCs.

Using atomic emission spectrometry, it is difficult to achieve high-sensitivity analysis of chlorine, due to its high excitation energy. Only 5% of the total sample volume contributes to the emission intensity, using a nebulizing system of inductively coupled plasma atomic emission spectrometry (ICP-AES). In this study we propose a new oxidation vaporization method, based on the introduction of gaseous chlorine into the plasma. High-sensitivity chlorine analysis has been achieved by this method, due to an almost 100% conversion of chlorine dissolved in the sample into the gaseous state. As a result, the sensitivity improvement achieved, and this new method can be used with the commercial introduction system, with a 20-times improved sensitivity for chlorine, compared with the typical nebulizing system. Results obtained by the new method were confirmed using mineral drinking water and river water. The measured values were almost identical to those obtained by ion chromatograph, while the measurement took only one minute.