Standard gas is well known as a reference gas or gas mixtures used as comparative standard in the calibration of analytical instruments, and the generation is grouped into static methods with gas cylinder and dynamic ones with diffusion and permeation tubes. In the case of acetaldehyde gas generation with a conventional permeation tube, more than one month of continuous generation has not been reported because the concentration of generated acetaldehyde significantly decreases within one month. Authors developed a novel permeation tube of acetaldehyde which aimed the lengthening of stable generation. A continuous monitoring of the concentration of acetaldehyde in the mixture was performed under different dilution gases (nitrogen and air) and temperatures (10, 20 and 30°C) by DNPH-HPLC method. A comparison of permeation rates obtained from HPLC analysis and mass loss of permeation tubes was also conducted. The results indicated that the permeability of acetaldehyde in nitrogen gas was 2320 ± 2.98 ng min-1 (k=2) at 10°C, and 6719 ± 0.87 ng min-1 (k=2) at 20°C. At 10°C and 20°C, the permeability of acetaldehyde determined with a mass loss of a tube showed constant for 3 months within the level of uncertainty and agreed with that from HPLC, whereas significant decrease at 30°C. These values agreed with those in the case of air. Acetic acid was detected in the residual solution in inside of the tube, whose permeability was negligibly small and had no effect on the concentration of generated acetaldehyde. An accurate acetaldehyde standard gas can therefore be provided using this permeation tube for 3 months, longer than one month with a conventional method, under the conditions of 10°C and 20°C.
The concentrations of insecticides in vacuumed house dust were analyzed as an indicator of indoor pollution in order to investigate the indoor exposure to insecticides. Here we describe the residue levels of six kinds of insecticides found in 69 house dust samples collected around Osaka from 2011 to 2015. The insecticides in dust samples were extracted with acetone under ultrasonic waves. Cleanup of insecticides in the extract was conducted using a graphite carbon column followed by a silica gel 40 mini column. Quantitative analyses of the insecticides were performed with GC by electron-capture detection or flame photometric detection using a capillary column. Chlorpyrifos was detected in 24 out of the 69 samples at a level of <0.010 to 0.48 μg/g. Diazinon was not detected in house dust at all. Fenitrothion was detected in 41 out of the 69 samples (max: 0.29 μg/g, median: 0.010 μg/g). Permethrin concentrations (max: 13 μg/g, mean: 1.7 μg/g, median: 0.36 μg/g) detected in the dust samples were highest among the six kinds of insecticides. Higher concentrations of permethrin were detected in the house dust collected from houses which were treated with termite control agents. S-421 (bis(2,3,3,3,-tetrachloropropyl) ether) was detected in 63 out of the 69 samples (max: 0.54 μg/g, mean: 0.057 μg/g). p-Dichlorobenzene was detected in 31 out of 38 samples. The concentrations of p-dichlorobenzene in two samples were higher than four times of those which have been detected in our studies thus far.
Methanol has become recognized as a potential air pollutant in our living environment because many new uses of methanol are being proposed including automotive fuel and hydrogen source for fuel cell. Manganese dioxide (MnO2) is practically used for a major ingredient of air cleaning materials, because it reacts with harmful formaldehyde to give stoichiometrical carbon dioxide even at room temperature. When methanol can be oxidized to formaldehyde by MnO2, methanol can be also converted to carbon dioxide at room temperature. Then, this study aimed to investigate the heterogeneous reaction between gaseous methanol and MnO2 powder in a closed bag under ambient temperature. The results showed methanol concentration in air successfully decreased with time depending on the specific surface area of the MnO2 samples, and significant conversion to carbon dioxide was found with a formation of trace amount of formaldehyde in air and formate species on the surface of MnO2 as intermediates. This means MnO2 also shows high activity in the deep oxidation of methanol to carbon dioxide even at room temperature.
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