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For on-site analysis of surface materials on the Moon, planets, and small bodies and for the monitoring of air quality in crewed spacecraft, we have developed a portable gas chromatograph (GC) equipped with a ball surface acoustic wave (SAW) sensor. In this study, we fabricated a 10 cm cube GC that implements the forward flush method using two metal micro-electro-mechanical-system columns coated with different stationary phases in microchannels fabricated by wet etching and diffusion bonding of stainless-steel plates. Using this GC, we succeeded in analyzing 10 kinds of gas within 10 min. In addition, for the application of the ball SAW GC on the ground, we also developed a palm-sized GC with a single metal capillary column and used it in the analysis of the headspace gas of sake. We showed that the ratio of peak areas differed among odorants depending on the brand and brewing process of sake. [ABSTRACT FROM AUTHOR]

The measurement of trace moisture is important in industry to maintain the quality and yield of products, such as semiconductors, lithium-ion batteries, and organic electroluminescence devices. In the field, on-site calibration of a trace moisture analyzer is required to maintain its reliability. Given these circumstances, we previously developed a ball surface acoustic wave (SAW) sensor using SAW on spherical piezoelectric elements and reported its quick response as its advantage over other trace moisture analyzers. However, the ultimately short response time of less than 1 s has not been verified, and it has not yet been calibrated on-site. In this study, we developed a system for the injection of saturated water vapor to evaluate the quick response of a trace moisture analyzer, and we verified the quick response time of as short as 0.64 s. It is the shortest response time reported so far. In addition, to realize its on-site calibration, we developed a dynamic calibration method, which takes only 10 min, by the injection of saturated water vapor, in contrast to the presently available static calibration method that takes 10 h. Since this system consists of simple components, it can be downsized. Moreover, because it uses a small amount of saturated water vapor as the calibration gas, it is easy to prepare calibration gases in the field and may be applied to on-site calibration. [ABSTRACT FROM AUTHOR]

Although portable gas chromatographs (GCs) have been developed for the monitoring of volatile organic compounds (VOCs) in working environments, they still need high power consumption for the heating column. Thus, we previously developed a portable surface acoustic wave (SAW) GC equipped with a ball SAW sensor and a micro-electromechanical-system column (ball SAW GC) and proved the usefulness of the forward flush (FF) method for realizing the fast analysis of multiple gases without a heater. However, its ability to measure ten kinds of VOCs at ppm order and automatic continuous measurement were not demonstrated. In this study, a ball SAW GC employing the FF method and equipped with a gas sampler for continuous injection was developed. Then, the performance of monitoring multiple gases in working environments was verified by measuring ten kinds of VOCs with maximum acceptable concentrations. Moreover, real-time monitoring of seven kinds of VOCs with a linear change in the response value to concentration changes was demonstrated. [ABSTRACT FROM AUTHOR]

In the field of environmental measurement and security, a portable gas chromatograph (GC) is required for the on-site analysis of multiple hazardous gases. Although the gas separation column has been downsized using micro-electro-mechanical-systems (MEMS) technology, an MEMS column made of silicon and glass still does not have sufficient robustness and a sufficiently low fabrication cost for a portable GC. In this study, we fabricated a robust and inexpensive high-precision metal MEMS column by combining diffusion-bonded etched stainless-steel plates with alignment evaluation using acoustic microscopy. The separation performance was evaluated using a desktop GC with a flame ionization detector and we achieved the high separation performance comparable to the best silicon MEMS column fabricated using a dynamic coating method. As an application, we fabricated a palm-size surface acoustic wave (SAW) GC combining this column with a ball SAW sensor and succeeded in separating and detecting a mixture of volatile organic compounds. [ABSTRACT FROM AUTHOR]