TY - JOUR
T1 - Direct detection of gas-phase mercuric chloride by ion drift - Chemical ionization mass spectrometry
AU - Khalizov, Alexei F.
AU - Guzman, Francisco J.
AU - Cooper, Matthew
AU - Mao, Na
AU - Antley, John
AU - Bozzelli, Joseph
N1 - Publisher Copyright:
© 2020 Elsevier Ltd
PY - 2020/10/1
Y1 - 2020/10/1
N2 - Mercury is a persistent environmental pollutant that enters the atmosphere mostly in elemental form (Hg0) and leaves in oxidized form. The atmospheric oxidation mechanism of Hg0 is inadequately constrained because of the limited direct experimental knowledge of molecular identities of gaseous oxidized mercury (GOM), severely hindering the evaluation of mercury deposition to the terrestrial and aqueous environment. Here we present the development and testing of a direct approach for laboratory detection of GOM, using the ion drift - chemical ionization mass spectrometry (ID-CIMS). In this approach, GOM reacts in an ion drift tube with an appropriate reagent ion to form well-defined product ions, which are detected by a quadrupole mass spectrometer equipped with a counting electron multiplier. We used HgCl2 as GOM surrogate, along with SF6−, CO3−, and NO3−⋅HNO3 as reagent ions, which were selected based on quantum chemical evaluations of several possible reaction mechanisms, including charge transfer, ion transfer, and ion-molecule clustering. All three reagent ions react with HgCl2 through one or more of the above mechanisms, providing a sensitivity sufficient for laboratory studies of atmospheric mercury chemistry. To make direct sampling of atmospheric GOM possible, the sensitivity must be improved, primarily through the use of the ambient pressure chemical ionization.
AB - Mercury is a persistent environmental pollutant that enters the atmosphere mostly in elemental form (Hg0) and leaves in oxidized form. The atmospheric oxidation mechanism of Hg0 is inadequately constrained because of the limited direct experimental knowledge of molecular identities of gaseous oxidized mercury (GOM), severely hindering the evaluation of mercury deposition to the terrestrial and aqueous environment. Here we present the development and testing of a direct approach for laboratory detection of GOM, using the ion drift - chemical ionization mass spectrometry (ID-CIMS). In this approach, GOM reacts in an ion drift tube with an appropriate reagent ion to form well-defined product ions, which are detected by a quadrupole mass spectrometer equipped with a counting electron multiplier. We used HgCl2 as GOM surrogate, along with SF6−, CO3−, and NO3−⋅HNO3 as reagent ions, which were selected based on quantum chemical evaluations of several possible reaction mechanisms, including charge transfer, ion transfer, and ion-molecule clustering. All three reagent ions react with HgCl2 through one or more of the above mechanisms, providing a sensitivity sufficient for laboratory studies of atmospheric mercury chemistry. To make direct sampling of atmospheric GOM possible, the sensitivity must be improved, primarily through the use of the ambient pressure chemical ionization.
KW - Atmosphere
KW - CCSD(T)
KW - Chemical ionization
KW - DFT
KW - Detection
KW - Mass spectrometry
KW - Mercury
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U2 - 10.1016/j.atmosenv.2020.117687
DO - 10.1016/j.atmosenv.2020.117687
M3 - Article
AN - SCOPUS:85087408309
SN - 1352-2310
VL - 238
JO - Atmospheric Environment
JF - Atmospheric Environment
M1 - 117687
ER -