Nanoparticle Characterization, Fundamental Studies and Computer Simulations of Dynamic Reaction Cell Inductively Coupled Plasma Mass Spectrometry

An Inductively Coupled Plasma Mass Spectrometer (ICP-MS) equipped with a Dynamic Reaction Cell (DRC) was used to study the effects of locating a pressurized reaction cell between the ICP ion source and quadrupole mass filter. Improvements in the precision of isotope ratio measurements and reductions of overlap signals by collision induced dissociation and ion-molecule reactions were shown as compared to ICP-MS without a DRC. The rate of signal decay from ion-molecule reactions was related to kinetic rate constants, and a simulation was written to visualize ion trajectories in the DRC. A new method of determining ion-molecule kinetic rate constants and efficiencies was established. Finally, ICP-MS was used to characterize nanoparticle sizes, particle mass distributions and elemental compositions of both single size standards and mixtures. Particular focus in this work was paid to relate fundamental concepts, models and simulations to experimental data in order to further understanding of ICP-DRC-MS.;High precision measurements might be acheived from a noisy sample source by passing the ion beam through the pressurized reaction cell and dampening signal fluctuations. Laser ablation was coupled to the ICP-DRC-MS to provide a noisy sample source and large signal fluctuations. Isotope ratio precision from a homogeneous solid sample was compared among ICP-DRC-MS, ICP-q-MS, ICP-SF-MS and ICP-OES. Counting statistics limited precision was achieved when the reaction cell was pressurized with NH3. Improved precision of trace metal concentration gradients mapped in both homogeneous and heterogeneous solid samples was found using a pressurized DRC.;Inert collision gases were tested to determine which polyatomic overlaps could be attenuated via collision induced dissociation (CID) without sacrificing analyte sensitivity. Ar offered the best compromise between efficient CID and minimal scattering losses. A simple calculation was shown to reliably predict under what conditions CID will occur, and polyatomic overlap reduction was related to bond energy and collision gas mass. CID was compared to ion-molecule reactions using a common spectral overlap, ArN+. Ion-molecule reactions were found to reduce the ArN+ signal more rapidly, but CID with Ar also offered blank contamination limited detection limits.;14 reaction gases were studied to determine the best gas for chemical resolution of all Se+ isotopes from argide, chloride and bromide matrices and rare earth overlaps in the +2 ionization state (REE2+ ). N2 and CO were found to provide contamination limited detection limits and produce no unwanted reaction chemistry, but could not resolve Se+ from REE2+ overlaps. Detection limits as low as 3 ng L-1 were measured for 80Se +. NH3 was found to improve the signal to background (S/B) ratio in matrices with high concentrations of REE's.;The chemical resolution of Sr+ from Rb+ was studied using SF6 reaction gas and a F atom addition reaction, which produced numerous unwanted byproducts. The byproducts were successfully rejected by operating the DRC as a low resolution mass filter.;A simple calculation based on gas effusion from the DRC was related ICP-DRC-MS signal decay rates to kinetic rate constants. A calibration procedure was derived and rate constants for the reaction between CH3F and both Ar + and Ar2+ were established for the first time. The method was also used to quantify the contributions of both CID and reactions to the rate of Ar2+ signal decay for 13 different gases.;SIMION 8.0, an ion trajectory simulation, was used to simulate ion-gas collisions in the DRC. The simulation used a hard sphere collision model to calculate the average number of ion-gas collisions and ion time of flight. The simulated collision rate was used to calculate reaction efficiencies that agreed well with values found in the literature when kinetic rate law assumptions were obeyed. The simulation was also used to visualize collisional focusing and scattering of the ion beam.;ICP-MS had not previously been used to characterize single nanoparticles with no pretreatment or separation. In this work, nanoparticles were delivered to the ICP-MS one at a time in dilute suspensions for mass and elemental characterization. The nanoparticle delivery system and influence of data recording and ICP parameters were discussed. Sensitivity, linear range and detection limits of single SiO 2 and Au nanoparticles were assessed. Additionally, nanoparticle mass and size distributions were compared and found slightly larger than those measured by SEM. Finally, 2 unknown mixtures were analyzed and correctly identified by ICP-MS, showing that ICP-MS is capable of analyzing both size and elemental mixtures of nanoparticles.