Energy-dependent Electrospray Mass Spectrometry

While fragmentation tends to be minimal for electrospray ionisation under normal conditions, it can be increased very conveniently by changing the voltage applied at the skimmer cones. Essentially, increasing the cone voltage causes 

HCHO loss (m/z 30) channel occurs relative to the CO loss (m/z 28) channel, but careful inspection reveals that the discontinuity probably occurs at m/z 969, i.e. [Ir4(CO)6 + OMe] loses HCHO to form the [Ir4H(CO)g] at m/z 939. Unequivocal confirmation of formaldehyde loss is provided by acquiring a conventional high-resolution mass spectrum at the appropriate cone voltage. 

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The following work describes our investigation into some unexpected chemistry resulting from our interest in unsaturated metal clusters. We study such systems primarily by mass spectrometry, and to assist these investigations we developed the new data presentation technique of energy-dependent electrospray mass spectrometry (EDESI-MS). One of the first systems studied was that of alkoxylated transition metal carbonyl clusters, which display loss of formaldehyde in their electrospray ionisation fragmentation process. We have been able to correlate this behaviour with macroscopic chemical properties of these clusters. 

Crawford, E., Dyson, P., Forest, O., Kwok, S. Mclndoe, J. S. Energy-dependent Electrospray Ionisation Mass Spectrometry of Carbonyl Clusters. 

Energy-dependent Electrospray Tandem Mass Spectrometry... 

Energy-dependent electrospray ionization mass spectrometry (EDESI-MS) uses a map of cone voltage versus mjz upon which ion intensity is plotted, which provides a complete picture of the fragmentation pattern particularly suitable for the structural analysis of mixtures. " ... 

Advances in spectroscopic characterization continue to drive the development of the field. A number of studies describing the mass spectrometry of medium- and high-nuclearity ruthenium and osmium carbonyl clusters have been reported, including UV-laser desorption, laser desorption/ionization time-of-flight and energy-dependent electrospray ionization the last mentioned has been shown to resolve mixtures of cluster compounds. 

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