Direct Analysis of Organometallic Compounds
Organometallic compounds play an important role in chemistry, as recently recognized by the awarding of the 2005 Nobel Prize in Chemistry to Chauvin, Schrock and Grubbs. Characterization of organometallic compounds by mass spectrometry can sometimes be complicated by problems with solubility and reactivity. Electron ionization can be used for some voltatile organometallics. Fast atom bombardment (FAB) and electrospray ionization (ESI) are useful provided suitable solvents can be used. Field desorption (FD) is often effective, but FD emitters can be fragile and the analysis should be carried out by an experienced operator.
DART (Direct Analysis in Real Time) complements these methods and provides an alternative; it is fast and does not require solvents. The sampling area is purged with an inert gas, reducing the likelihood of undesirable reactions. Further, AccuTOF-DART permits exact mass measurements without requiring the presence of a reference standard during the sample measurement. DART is extremely robust and does not require special operator training.
Mass spectra of several organometallic compounds were obtained by using DART. A few dry particles of each compound were placed in front of the DART source on a melting point tube and mass spectra were obtained within seconds. The best results were obtained by using small quantities of sample; very large quantities can result in ion-molecule reactions between sample ions and sample neutrals, resulting in isotopic patterns characterized by both M+.and [M+H]+. All labeled assignments were confirmed by exact mass measurements and isotope pattern matching.