Masahiko Numata

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Chlorine isotope fractionation during reductive dechlorination of trichloroethene (TCE) and tetrachloroethene (PCE) to cis-1,2-dichloroethene (cDCE) by anaerobic bacteria was investigated. The changes in the 37Cl/35Cl ratio observed during the one-step reaction (TCE to cDCE) can be explained by the regioselective elimination of chlorine accompanied by the(More)
The effects of saponification conditions (temperature and water content of saponifying solution) on the determination of chlorinated biphenyls (CBs) in marine sediments were investigated. Although highly chlorinated biphenyls (nona- to deca-CBs) decomposed during high-temperature saponification, the degree of degradation was reduced by adding water to the(More)
For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160°C for 40 min was best for extracting(More)
The potential of alkylammonium ion-bonded silica stationary phases for effective and simple pretreatment for determination of polychlorinated biphenyls (PCBs) in mineral oil samples is presented in this paper. The separation between PCBs and aliphatic hydrocarbons by normal phase chromatography was improved by using the alkylammonium ion-bonded silica(More)
Two marine sediment certified reference materials, NMIJ CRM 7304-a and 7305-a, have been issued by the National Metrology Institute of Japan in the National Institute of Advanced Industrial Science and Technology (NMIJ/AIST) for the determination of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). The raw materials of the CRMs were(More)
A proficiency test for the analysis of pesticide residues in brown rice was carried out to support upgrading in analytical skills of participant laboratories. Brown rice containing three target pesticides (etofenprox, fenitrothion, and isoprothiolane) was used as the test samples. The test samples were distributed to the 57 participants and analyzed by(More)
Proficiency testing was organized by the National Metrology Institute of Japan (NMIJ) as a measure of analytical competency in the quantification of pesticide residues in husked wheat powder. Seventy-one participants submitted analytical concentrations of the target pesticides (diazinon, fenitrothion, malathion, and etofenprox) along with details of the(More)
More than 100 independent strains ofThiobacillus ferrooxidans were isolated from six different domestic mining sites. Although there was some variation according to sampling site, about 73% of all strains carried more than one plasmid ranging in size from about 2.0 to 30 kilobase-pairs(kb). Among these, four plasmids of 2.4, 4.7, 5.1, and 8.9 kb, designated(More)
We have investigated the differences in response ratios of native polycyclic aromatic hydrocarbons (native PAHs)/13C-labeled PAHs (13C-PAHs) and of native PAHs/deuterium-labeled PAHs (PAHs-d) in a calibration solution containing at trace concentrations (< 1 microg mL(-1)) by gas chromatography-mass spectrometry. Only the ratios of native PAHs/PAHs-d(More)
The efficiency of microwave-assisted extraction (MAE) was evaluated for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish. An isotope dilution method was used for quantification via analysis of the samples by gas chromatography and mass spectrometry. MAE solvent, temperature, and time were optimized, and observed(More)