Determination of the particle counting efficiency and chemical sensitivities of an aerosol time of flight mass spectrometer under ambient sampling conditions

Abstract Recently developed aerosol time-of-flight mass spectrometer (ATOFMS) instruments are capable of determining the size and chemical composition of single particles (Noble and Prather, 1996, Gard et al. , 1997). These instruments provide convenient determination of atmospheric aerosol composition on a single particle basis in real time. To date, data from these instruments have been used qualitatively to study both the sources of ambient aerosols (Liu et al. , 1997) and the atmospheric transformation of particles (Gard et al. , 1998). However, quantitative reconstruction of a continuous time series of the actual size distribution and chemical composition of atmospheric aerosols requires that the absolute counting efficiency and chemical sensitivities of these instruments be known.