BUNSEKI KAGAKU Abstracts

Dechlorane Plus is a highly chlorinated flame retardant, which was developed as an alternative of Mirex (Dechlorane), banned in the 1970s. Investigation reports are increasing rapidly recently in the United States, Canada and China. However, to our knowledge, no data for levels of Dechlorane Plus in the environment are available in Japan. Therefore, we measured Dechlorane Plus by using the GC/high-resolution MS in EI mode, and identified this compound in environment samples collected from Japanese urban areas. This paper represents the first report of Dechlorane Plus in the Japanese environment. Dechlorane Plus was detected in house dust, deposits of window frames, road sediment, garden soil and sediment samples at concentrations ranging over 2.9–42 ng g⁻¹-dry, 240–270 ng g⁻¹-dry, 74–150 ng g⁻¹-dry, 1.7 ng g⁻¹-dry, 17–140 ng g⁻¹-dry, respectively. Further we showed the mean of anti-Dechlorane Plus fractional abundance (f_anti) values in these Japanese samples to be 0.65, 0.83, 0.80, 0.81, 0.81, respectively. The levels of Dechlorane Plus and the f_anti values in Japan were similar to those from studies in China and Canada. Also, we noticed that care must be taken to temperature and dilution solvent to stock a high concentration of the anti-Dechlorane Plus standard solution. More research is required to elucidate the environment levels and the sources of Dechlorane Plus in Japan.

Aromatic pollutants (toluene, chlorobenzene, 1,2-dichlorobenzene and 1,4-dichlorobenzene) and their deuterium substitutes were determined by a gas chromatograph equipped with a finger-sized atomic emission detector (AED) using helium radio-frequency plasma. Incomplete spectral separation between the atomic emissions of hydrogen and deuterium at 656.28 nm and 656.10 nm, respectively, was performed using a small CCD spectrometer (optical resolution : 0.035 nm). The emissions were, however, possible to be measured separatively, due to complete gas-chromatographic separation between the aromatics and their corresponding deuterium substitutes using a GC capillary column. When the flow rate of the make-up (helium) gas, applied power and frequency were optimized to be 5 mL min⁻¹, 20 W and 220 kHz, respectively, the detection limits (3σ) of hydrogen in toluene and deuterium in toluene-d₈ were estimated to be 28 pg and 42 pg, respectively. The aromatic pollutants in tap water extracted by head-space solid-phase microextraction were successfully determined by the GC-AED at the ppb level using deuterium-substituted surrogated compounds as the internal standards.

As diagnostic techniques for evaluating the biological effect of environmental chemicals, we have developed novel electrochemical gene sensors without labeling target DNAs and without using external indicators. We revealed that the developed sensors detect target DNAs easily and rapidly with detection limits at less than pM levels. We also fabricated electrochemical gene sensor array chips as devices that integrate the developed sensors, and demonstrated multiple gene detection. Moreover, a liquid spotting technique was also developed with higher precision in dispensing lower volumes compared to those for conventional pipette tip-type dispensers, required in fabricating integrated gene sensor array chips, and was revealed to have a ripple effect to other analytical techniques. These developed techniques will become platforms for simple and rapid environmental diagnostic techniques providing primary screening methods applicable to clinical and environmental practices.

The mixing of N,N'-bis(2,4-di-sulfobenzyl)tolidine tetrasodiumsalt (SBT), residual chlorine and ascorbic acid showed the binary color (colorless and light blue) in the wells of a microplate. Here, SBT acts as a chromogenic reagent for residual chlorine, and ascorbic acid acts as an inhibitor of the SBT reaction. The concentration of the sample with changing of the color can be controlled by adjusting the ascorbic acid concentration. Therefore, when an unknown concentration’s residual chlorine solution was added into the microplate wells, which are contained at several concentrations of ascorbic acid solution with SBT, the number of discoloring wells changed according to the concentration of the residual chlorine. Based on these findings, the on-off type of visual analysis for residual chlorine by the counting of colorless wells was developed. As a result, the absorbance at 675 nm by the SBT method could not be observed until the residual chlorine was over that of the ascorbic acid. In the proposed method, the concentration of residual chlorine could be determined in the range of 3.0 × 10⁻⁵ to 2.4 × 10⁻⁴ mol L⁻¹. Moreover, the proposed method could be applied to tap water that is spiked at a known-concetration of residual chlorine, and satisfactory results were obtained.

A simple and selective method was developed for the determination of enantiomeric glycidyl fatty acid esters (GE) in refined edible oils, which are undesirable trace contaminants formed during refining processes. For this purpose, chiral-phase high-performance liquid chromatography (HPLC) was performed with a column containing amylose tris(3,5-dimethylphenylcarbamate) as a chiral selector, using an acetonitrile/methanol mixture as the mobile phase, which gave clear enantiomer resolution of synthetic saturated and unsaturated GE racemates. This was followed by on-line atmospheric pressure chemical ionization mass spectrometry (APCI/MS) to obtain prominent protonated [M＋H]^＋ molecules, by which individual GE molecules could be identified and quantified. The quantification of GE enantiomers was performed in the selected ion monitoring (SIM) of [M＋H]^＋ . This chiral-phase HPLC/APCI-MS-SIM method was standardized with synthetic GE racemates, and applied to the separation, identification and quantification of individual GE enantiomers in a commercial diacylglycerol (DAG)-rich oil produced originally from soybean oil and rapeseed oil. The results clearly showed that the DAG-rich oil contained almost equal amounts of R- and S-enantiomers of glycidyl palmitate (16 : 0-GE), stearate (18 : 0-GE), oleate (18 : 1-GE), linoleate (18 : 2-GE), and linolenate (18 : 3-GE), suggesting that both enantiomers would be formed from the corresponding almost racemic 1-monoacylglycerols. The most predominant GE was 18 : 2-GE, followed by 18 : 1-GE, which accounted for 107 and 25 μg g⁻¹, respectively, reflecting the fatty acid composition of the DAG oil.

In this work, we obtained a protein that passed through an ultrafiltration membrane of 100 kDa and was retained on that of 30 kDa from the hepatopancreas of scallop. We measured the molecular weight of the protein by MALDI-TOF-MS, and evaluated the affinity of metal cations to it. The molecular weight of the protein was found to be around 20 kDa, despite the fact that the proteins were retained on a 30-kDa ultrafiltration membrane. Consequently, we poured a portion of EDTA solution onto the ultrafiltration membrane holding the protein. As a result, it passed through the 30-kDa ultrafiltration membrane. This implies that the protein may be dissociated by removing metal cations. Next, we studied the affinity of Cd^2＋, Cu^2＋, Ni^2＋, and Pb^2＋ to the protein immobilized on Sepharose (p-Sepharose). Adsorption isotherms were prepared to obtain the adsorption capacity and the adsorption constant by employing the Langmuir model. The order of the adsorption capacity was Cu^2＋＞Ni^2＋＞Cd^2＋≒Pb^2＋. The mole ratios of metal cations to protein were 0.24 for Cd^2＋, 2.00 for Cu^2＋, 0.37 for Ni^2＋, and 0.24 for Pb^2＋. Mole ratios less than 1 support a hypothesis derived from MS measurements, that the proteins may associate with each other via metal cations. The order of the adsorption constant was Cu^2＋＞Cd^2＋＞Ni^2＋＞Pb^2＋. The Cd^2＋, which has a large ionic radius, has a low adsorption capacity, but does have the second largest adsorption constant. We confirmed a strong affinity of heavy metal cations to the protein in hepatopancreas of scallop.

The solid-phase extraction (SPE) of palladium(II) using resins impregnated with 8-quinolinol derivatives (HQs) with a long-chain alkyloxymethyl group from acidic solutions was investigated. The HQs used were 5-octyloxymethyl-8-quinolinol (HO₈Q) and 7-bromo-5-octyloxymethyl-8-quinolinol (HBrO₈Q). Palladium(II) was quantitatively extracted from 5 M HNO₃ with HQs-impregnated resins and from 2 M HCl with HBrO₈Q-impregnated resins. The selective extraction and recovery of palladium(II) from a simulated spent autocatalysts solution and a simulated high-level radioactive waste solution could be accomplished using HQs-impregnated resins.

The elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) has become increasingly important as a potential powerful tool for food authenticity. However, the lack of a reliable technique for the isotope ratio measurement, and limited availability of adequate international references are significantly regrettable, and should be improved immediately. Here we present results of an inter-laboratory test on the EA-IRMS determination of stable carbon, nitrogen and oxygen isotopic compositions (δ¹³C, δ¹⁵N and δ¹⁸O) in organic compounds. Three organic compounds (L-alanine for δ¹³C and δ¹⁵N, and 1,2,3,4,6-penta-O-acetyl-α-D-glucopyranose and Dimethyl aminoterephthalate for δ¹⁸O) were distributed and analyzed by a total of 25 laboratories. The results show that the 1σ standard deviation among laboratories is −11.9±0.2 ‰ (for δ¹³C), −2.6±0.3‰ (for δ¹⁵N), ＋32.3±1.0‰ (for δ¹⁸O of the glucopyranose derivative), and ＋25.9±2.3‰ (for δ¹⁸O of Dimethyl aminoterephthalate). Although the variations of the standard deviations for δ¹³C, δ¹⁵N and δ¹⁸O (glucopyranose derivative) among laboratories are not so large compared to the instrument uncertainties, δ¹⁸O of Dimethyl aminoterephthalate, which contains nitrogen, shows a large variation among laboratories. This may have been caused by much contamination of N₂ to the CO peak on the EA-IRMS chromatogram, and may be improved by using a longer GC column (1.0∼1.5 m) for chromatographic separation.