Technical Note: Description and Use of the New Jump Mass Spectrum Mode of Operation for the Aerodyne Quadrupole Aerosol Mass Spectrometers (Q-AMS)

A new mode of operation for the Aerodyne Quadrupole Aerosol Mass Spectrometer (Q-AMS) has been developed and used to improve the detection limits and time resolution of the instrument. The Jump Mass Spectrum (JMS) mode works by stepping through a small number of specific user defined positions within the mass spectrum, increasing the time spent scanning specific m/z’s. The JMS mode is conceptually similar to the “Selected Ion Monitoring” mode of some commercial quadrupole-based instrumentation and can be used for direct quantification when the fragmentation pattern is known. The JMS mode can also be used to augment the standard Q-AMS operation in Mass Spectrum mode when the fragmentation pattern is not known, improving the effective signalto-noise ratio (SNR) and in turn the detection limits and time resolution. A decrease in detection limits for the Q-AMS by factors of 4.6, 3.9, 1.3, and 3.5 for nitrate, sulphate, total organics, and m/z 43 mass loadings respectively was achieved for 1 minute sampling (20 s in each of the three Q-AMS modes, monitoring 10 m/z in JMS mode). Although the benefit to the SNR of the total organic mass