Evaluation of a particle trap laser desorption mass spectrometer (PT-LDMS) for the quantification of sulfate aerosols

The PT-LDMS was evaluated by both laboratory and ambient measurements, with the focus being the quantification of sulfate aerosols. Ammonium sulfate ((NH 4 ) 2 SO 4 ) is generally the predominant form of sulfate aerosols in urban air; hence, it is used as a material for laboratory experiments and calibration.

Major fragments of (NH 4 ) 2 SO 4 were observed at mass-to-charge ratios ( m / z ) of 48 (SO + ) and 64 (SO 2 + ). The dependence of sensitivity (expressed as the ratio of m / z 48 signal to sulfate mass) on laser power and cell temperature was investigated. An intercomparison of PT-LDMS with a commercial sulfate particle analyzer (SPA) and filter sampling was performed in Tokyo.