Aerosol Spectrometer for Measuring Diameters and Chemical Compositions of Particulate Organic Matter Using a GC-MS Equipped with an Adsorption-Thermal Desorption Tube

摘要

We describe the design and performance of an aerosol spectrometer that simultaneously measures the size-dependent number concentration and chemical composition of particulate organic matter. The spectrometer consists of a differential mobility analyzer (DMA) for size classification and a gas chromatograph-mass spectrometer (GC-MS) for composition analysis. Size-classified particles of an aromatic hydrocarbon were directly introduced into a thermal desorption (TD) tube packed with adsorbent. Then, thermally desorbed aromatic hydrocarbon molecules were introduced into the GC-MS. Comparisons between the number concentrations of the classified particles measured with a Faraday cup electrometer and the peak area of nonylbenzene in the chromatogram of the GC-MS determined the detection limit of our spectrometer. For a particle size of 330 nm, the lower detection limit of the spectrometer was found to be approximately 2x10~3 particles/cm~3 for an adsorption time of 30 seconds. This value was approximately 1/25 of the value of 5x104 particles/cm~3 reported as the lower detection limit in our previous work (Okada et al., 2010).