Analytical Sciences

Selective Concentration of Ultra-trace Acetone in the Air by Cryogenic Temperature Programmed Desorption (cryo-TPD)

Taku T. SUZUKI and Isao SAKAGUCHI

National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan

A gas analytical technique with compact size, low cost, sufficient sensitivity, and excellent reproducibility is required in many fields including exhaled breath analysis for medical monitoring. In the present study, we examined selective acetone concentration by quench condensation at cryogenic temperature followed by temperature programmed desorption (cryogenic temperature programmed desorption (cryo-TPD)) for possible applications to breath analysis for medical monitoring. The essence of cryo-TPD is rough mass selection by thermal desorption followed by quantification of certain species using mass spectrometry. The performance of cryo-TPD was investigated in the acetone concentration range below 1 × 10⁻⁶ volume fraction (1 ppmv). It was found that acetone is selectively quench-condensed on a tungsten substrate at 50 K without the major components of air, such as N₂ and O₂. The concentrated acetone gas was obtained by the following thermal desorption at around 151 K. Under conditions of condensation for 1 min and pressure of 1 × 10⁻² Pa, the lowest limit of detection reached well below 10 × 10⁻⁹ volume fraction (10 ppbv). The relationship between the cetone intensity of cryo-TPD and the acetone concentration in the gas was almost linear in the ppbv range. The separation of acetone and propanal using the fragmentation pattern, which have almost the identical molecular mass, was also demonstrated in the present study.

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