Real-time chemical analysis of aerosol particles

An important aspect of environmental atmospheric monitoring requires the characterization of airborne microparticles and aerosols. Unfortunately, traditional sample collection and handling techniques are prone to contamination and interference effects that can render an analysis invalid. These problems can be avoided by using real-time atmospheric sampling techniques followed by immediate mass spectrometric analysis. The former is achieved in these experiments via a two state differential pumping scheme that is attached directly to a commercially available quadruple ion trap mass spectrometer. Particles produced by an external particle generator enter the apparatus and immediately pass through two cw laser/fiberoptic based detectors positioned two centimeters apart. Timing electronics measure the time between detection events, estimate the particles arrival in the center of the ion trap and control the firing of a YAG laser. Ions produced when the UV laser light ablates the particle`s surface are stored by the ion trap for mass analysis. Ion trap mass spectrometers have several advantages over conventional time-of-flight instruments. First, they are capable of MS/MS analysis by the collisional dissociation of a stored species, This permits complete chemical characterization of airborne samples. Second, ion traps are small and lend themselves to portable, field oriented applications