Laser desorption/ionization coupled to tandem mass spectrometry for real-time monitoring of paraquat on the surface of environmental particles

Aerosol mass spectrometry with laser desorption/ionization was investigated as a possible tool for real-time monitoring of the presence of the pestici de paraquat on the surface of airborne soil particles, Laser desorption/ion ization of paraquat dication produced only singly charged ions. The most ab undant species were [M](+.), [M - H](+), and [M - CH3](+). Operation of the ion trap mass spectrometer in the MS3 mode allowed the reduction of the si gnal dependence on laser fluence fluctuations and permitted the detection o f the analyte with good sensitivity and high selectivity, The estimated lim it of detection in terms of surface coverage was 0.016 monolayers, approxim ately 1 attomole of paraquat on the surface of a single micronsized soil pa rticle. Copyright (C) 2000 John Wiley & Sons, Ltd.