FIGAERO-iodide-CIMS
A sample flow was directly drawn into a turbulent flow ion-molecule reactor (IMR). Gaseous products were ionized as their corresponding adduct ions with I-. Particulate products collected on the PTFE membrane filter were desorbed by a flow of heated UHP N2. The temperature of the N2 increased from 20 to 200 oC in 50 min. The desorbed molecules entered the IMR and were charged by the same ionization mechanism. Background HNO3 was inevitable in the experimental apparatus containing macroalgae and natural seawater. So the cluster ions containing NO3- or HNO3 were observed occasionally. ToF-MS was configured to measure singly charged molecular ions of 7-720 Th with a MS resolution of ~4500. Mass calibration was conducted using the ions of NO3-, CF3O-, C2F3O2-, C3F5O2-, I3-for gaseous products and NO3-, I-, IHNO3-, IC2F3HO2-, I3-for particulate products. Reliable formula identification of ion peaks was corroborated by high accuracy of fits (<20 ppm) and isotope patterns. Background signal in the gas phase was determined by measuring a UHP N2 flow. The signal during the last 3 minutes of the soak period of PTFE membrane filter was regarded as background signal in the particle phase. Background signals were then subtracted from the intensities of compound formulas.