Aerosol particle analyzer (APA) for measuring the amount of analyte in airborne particle is described. The APA uses an analysis liquid. In most embodiments, this analysis liquid is chosen so that when it is mixed with the particles, an optical property of the analysis liquid (AL) varies according to the amount of the analyte in the particles. Airborne particles are drawn into the instrument, and detected using optical methods such as light scattering or laser-induced fluorescence. When a particle of interest is detected, a charged droplet of the analysis liquid (CDAL) is ejected so that it collides with the detected particle and moves into a horizontally oriented linear quadrupole that is in an airtight container, except for small orifices to let the CDAL enter and exit. The CDAL is levitated in a high humidity environment so that it evaporates slowly, so that there is time for the reaction between the analyte, if any, and the CDAL can take place, and so that the optical property, typically fluorescence, can be measured. The amount of the analyte in the particle is determined from the measured fluorescence or other optical property. The particles collected into the CDAL can be sent on to other instruments for further analysis, especially to instruments that can analyze such small samples.