Tsuneaki Maeda

Practical guide for accurate quantitative solution state NMR analysis

A practical guide to experimental conditions such as statistical variation of signal intensity on quantitative solution state nuclear magnetic resonanace (NMR) analysis is discussed and presented. Statistical analysis showed that there is a relationship between a targeted precision and practical pulse intervals. The bandwidth of the audio filter needs to be set so that all the signals of interest fall into 80% of the centre part of the filter. When fulfilling these conditions, the relative standard deviation (RSD) of a signal area in repeated experiments can be estimated by determining the signal-to-noise ratio (SN) of a single spectrum. When the SN reached 1000, the RSD became constant with increasing SN. With such a condition, accuracy better than 1% should be obtained with quantitative NMR.

Development of analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates: A review

In the present work, the different sample collection, pretreatment and analytical methods for polycyclic aromatic hydrocarbons (PAHs) in airborne particulates is systematacially reviewed, and the applications of these pretreatment and analytical methods for PAHs are compared in detail. Some comments on the future expectation are also presented.

C2–C5 hydrocarbon concentrations in Central Osaka

Abstract Hourly measurements of nine C 2 –C 5 hydrocarbons (HCs) were made over a period of 15 months in the center of Osaka City, Japan. The measurements were made by using an automated system consisting of a combination of a gas preconcentrator and a gas chromatograph. The concentrations of all components were high in early winter and low in summer. The highest concentration was of C 2 H 4 , while C 3 H 6 showed the lowest concentration throughout the year, and was rarely detected in summer. There were small annual variations in the concentrations of C 4 –C 5 HC. The chemical reactions that affect HC concentrations were also examined. The seasonal C 2 H 4 /C 2 H 2 and C 3 H 6 /C 2 H 2 ratios were compared, taking into account that C 2 H 4 , C 2 H 2 , and C 3 H 6 are mainly from vehicles and the differences in their reactivities. Despite the high reactivity of C 2 H 4 , the C 2 H 4 /C 2 H 2 ratio was low in winter and high in summer, with the result that the C 2 H 4 consumption by chemical reaction seemed small in the center of the city. The behavior of C 3 H 6 /C 2 H 2 is opposite to that of C 2 H 4 /C 2 H 2 , illustrating the more reactive characteristics of C 3 H 6 . Regarding the effect of photochemical reactions, it was observed that HC’s levels drop as NO 2 /NO x increases. Though the slope does not show a direct proportionality to HC reactivity, reactivity of C 3 H 6 , which is the most reactive HC among the nine measured HCs, showed the largest declines. The ratio of C 4 –C 5 HC to the C 2 –C 5 HC rose with increase in ambient temperature, while the ratio of C 2 –C 5 HC to the nonmethane hydrocarbons decreased. This phenomenon was correlated with ambient temperature, indicating higher emissions of higher molecular weight HCs in summer.

On-site monitoring of volatile organic compounds as hazardous air pollutants by gas chromatography

There are a large number of organic components in air. These components can be classified in six groups. On-site monitoring procedures for two of these groups, oxidant precursors and hazardous air pollutants, are reviewed. For hazardous air pollutants, mainly long-term data are required. Oxidant precursors, however, some of which are very volatile, must be detected and quantified as early and as rapidly as possible. The monitoring techniques differ accordingly. Considerations governing on-site monitoring methods for both purposes are discussed.

An automated purge and trap gas chromatography-mass spectrometry system for the sensitive shipboard analysis of volatile organic compounds in seawater

a) Department of Ocean Sciences, Tokyo University of Fisheries, 4-5-7 Konan, Minatoku, Tokyo 108–8477, Japan b) National Institute for Resources and Environment, 16-3 Onogawa, Tsukuba, Ibaraki 305–8569, Japan c) DKK Corporation, 4-13-14 Kichijoji Kitamachi, Musashinoshi, Tokyo 108-0001, Japan An automated purge and trap gas chromatographymass spectrometry system for the sensitive shipboard analysis of volatile organic compounds in seawater

Development of mass measurement equipment using an electronic mass-comparator for gravimetric preparation of reference gas mixtures

The gravimetric method is the most popular method for preparing reference gas mixtures with high accuracy. We have designed and manufactured novel mass measurement equipment for gravimetric preparation of reference gas mixtures. This equipment consists of an electronic mass-comparator with a maximum capacity of 15 kg and readability of 1 mg and an automatic cylinder exchanger. The structure of this equipment is simpler and the cost is much lower than a conventional mechanical knife-edge type large balance used for gravimetric preparation of primary gas mixtures in Japan. This cylinder exchanger can mount two cylinders alternatively on the weighing pan of the comparator. In this study, the performance of the equipment has been evaluated. At first, the linearity and repeatability of the mass measurement were evaluated using standard mass pieces. Then, binary gas mixtures of propane and nitrogen were prepared and compared with those prepared with the conventional knife-edge type balance. The comparison resulted in good consistency at the compatibility criterion described in ISO6143:2001.

Calibration of an evaporative light-scattering detector as a mass detector for supercritical fluid chromatography by using uniform Poly(ethylene glycol) oligomers.

The quantitativeness of an evaporative light-scattering detector (ELSD) for supercritical fluid chromatography (SFC) was evaluated by using an equimass mixture of uniform poly(ethylene glycol) (PEG) oligomers. Uniform oligomers, in which all molecules have an identical molecular mass, are useful for the accurate calibration of detectors. We calibrated the SFC-ELSD system for various concentrations and molecular masses by using an equimass mixture of PEG oligomers. ELSD not only showed a good linear response to the injected concentration over a wide concentration range, from 10(-4) to 10(-1)g/mL, but also showed a strong dependence on the molecular mass of the solute. By using chromatograms of the equimass mixture of uniform oligomers to calibrate SFC-ELSD, it was possible to determine exact values of not only the average mass but also the molecular-mass distribution for a PEG 1540 sample. The average molecular mass was shifted to a higher value by several percentage points after calibration of the ELSD.

Determination of very volatile organic compounds in environmental water by injection of a large amount of headspace gas into a gas chromatograph

An injection method for a large amount of headspace gas which enables determination of trace amounts of very volatile organic compounds (VVOCs), dichlorodifluoromethane, chloromethane, vinyl chloride, bromomethane, chloroethane and trichlorofluoromethane in all kinds of environmental water was developed. A gas phase equilibrated with the water phase in a vial was purged with helium for a short time. The VVOCs were then introduced into a trapping tube packed with Tenax TA, which had been cooled using carbon dioxide. After trapping, the VVOCs were thermally desorbed and put into a GC-MS system for subsequent analysis. This method is applicable to various types of samples.

Simplification of determination method for standard materials using post-column reaction GC/FID.

For the simple and fast preparation of highly reliable standard materials, a post-column reaction GC/FID system was developed and evaluated on the mixture of oxygen-containing organic compounds. The oxygen-containing organic compounds mixing solution were determined with the post-column reaction GC/FID system using n-dodecane as an internal calibration standard. Required value of relative expanded uncertainty as an original source of SI-traceable standard materials was within 1% and it aimed at this value as accuracy of the quantitative analysis. The results showed good agreement between the prepared concentrations and analytical values using post-column reaction GC/FID system. These results indicated that the post-column reaction GC/FID system would be used for getting SI-traceable values.

On-site monitoring system for hazardous air pollutants using an adsorption-thermal desorption-capillary GC system equipped with a photoionization detector and an electrolytic conductivity detector

Keywords: Adsorption/thermal desorption sampling instrument; capillary gas chromatography; electrolytic conductivity detector; photoionization detector; environmental air monitoring; hazardous air pollutants; volatile organic compounds