Ambient Mass Spectrometric Detection of Organometallic Compounds Using Direct Analysis in Real Time

The present work describes the mass spectrometric detection of organometallic compounds following their atmospheric pressure ionization using a commercial direct analysis in real time (DART) ion source. Several organometallic compounds of As, Fe, Hg, Pb, Set and Sri were examined, and their corresponding mass spectra as well as induced fragmentation patterns were recorded. Gas phase sampling of the pure organometallic compounds or their solutions prepared in toluene generated temporally stable signals. For the majority of the compounds, the molecular ion or protonated molecule was detected; noticeable exceptions are the tetra-substituted compounds for which their less-substituted species dominated. The organometallic species were used as model compounds for a systematic investigation of the impact of operating parameters of the DART source, including gas temperature and electrode voltages. In general, results have shown that powering the electrodes designed to remove ions from the DART gas stream results in a reduction in signal intensity for most of the compounds investigated, suggesting that charged species from the plasma play an important role in the ionization process of the test analytes.