Trends and Advances in Inductively Coupled Plasma Tandem Quadruple Mass Spectrometry (ICP-QMS/QMS) With Reaction Cell

Trends and advances in the development and application of inductively coupled plasma tandem quadrupole mass spectrometry (ICP-QMS/QMS) with a reaction cell is reviewed mainly based on publications from January 2018 to July 2021. ICP-QMS/QMS has been applied in various research fields covering the sciences of biology, energy, environmental, food/medical, geology, materials, and radionuclide. The objectives of analysis cover the determination of elemental concentration, ion-gas reaction, isotope analysis, single particle analysis, and chemical speciation analysis. Measurement of most elements in the periodic table are reported except for H, N, O, F, rare gas, and some of the radionuclides. In addition to the default reaction/collision gases (i.e., He, H2, O2, and NH3), N2O, CO2, CH4, CH3F, C2H4, and C2H6 have been used as reaction gases to improve the capability of separating spectral interferences or to study the ion-molecule reactions. Typical applications of ICP-QMS/QMS analysis in the major research fields are also discussed.

Are iodic acid measurements by chemical ionization unambiguous?

<p>Field observations of IO<sup>3−</sup> and HIO<sup>3−</sup>-containing cluster anions by chemical ionization–atmospheric pressure interface–time-of-flight mass spectrometry (CI-API-ToF-MS) have been reported1. These observations, which employ nitrate (NO<sup>3−</sup>) reagent ions for reaction with the analytes, have been interpreted as resulting from atmospheric gas-phase iodic acid (HOIO<sub>2</sub>) and molecular cluster formation via HOIO<sub>2 </sub>addition steps. CI-API-ToF-MS chamber measurements with alternative ionization schemes have also reported signals that could be attributed to gas-phase HOIO and HOIO<sub>2</sub>. However, well-established chemical kinetics and thermochemistry do not indicate any straightforward route to gas-phase iodine oxyacids and HOIO2 particle formation in the atmosphere. This does not only hinder the ability of chemical models for linking iodine emissions and particle formation, but also calls into question the interpretation of these CI-API-ToF-MS measurements. It has been proposed that water plays an important role in generating gas phase and HOIO<sub>2</sub>-containing molecular clusters, but recent flow tube experiments have established extremely low upper limits to the rate constants of possible reactions between iodine oxides (IO<sub>x</sub> and I<sub>x</sub>O<sub>y</sub>) and water. In this presentation, we discuss experimental and theoretical kinetics and thermochemistry of proposed routes to gas-phase HOIO and HOIO<sub>2</sub> in the atmosphere as well as potential ion-molecule reactions turning iodine oxides into IO<sup>3-</sup> ions in the CI-API-ToF-MS inlet. We show that there is an important ambiguity in the interpretation of IO<sup>3- </sup>and other signals observed with CI instruments as a result of barrierless reactions between I<sub>x</sub>O<sub>y</sub> and the reagent ions. Experiments for solving this ambiguity and reconciling conflicting results are proposed.</p>