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.