On the use of breakdown graphs combined with energy‐dependent mass spectrometry to provide a complete picture of fragmentation processes

Abstract

Both breakdown graphs and energy-dependent (ED) maps provide a means of visually representing the fragmentation processes resulting from collision-induced dissociation at different energies. The two presentation methods may be combined for a complete picture of the appearance, disappearance and maximum abundance collision potentials of each of the ions involved in the fragmentation process. A demonstration of this approach is presented using two very different classes of compound, an amino acid and a transition metal carbonyl cluster. Copyright # 2002 John Wiley & Sons, Ltd.Electrospray ionisation mass spectrometry (ESI-MS) is an enormously versatile analytical technique, allowing the collection of molecular weight data on a huge range of compounds hitherto inaccessible to mass spectrometry. 1Modern electrospray mass spectrometers also incorporate means of fragmenting ions produced in the ESI process, usually by collision-induced dissociation (CID) 2 either at the skimmer cone, in a collision cell or inside an ion trap or FTICR cell. 3 The extent of CID can be smoothly varied depending on the degree of fragmentation required, and the resulting ions provide useful structural information. A huge amount of data may be gathered in this way, and we have recently introduced the technique of energy-dependent electrospray ionisation mass spectrometry (EDESI-MS) as a convenient means of presenting this data. 4 It essentially involves a 2D projection (collision energy vs. m/z) of a 3D surface (the 3rd dimension, ion intensity, is on the axis perpendicular to the paper). The major advantages of this method are concise illustration of the data from up to 200 spectra and easy visualisation of the fragmentation sequence. EDESI-MS is a comprehensive solution to the problem of data presentation compared with the traditional approach of a stacked series of selected spectra. 5 We have recently extended the technique to laser-desorption/ionisation mass spectrometry (EDLDI-MS), 6 and, in the MS/MS mode, the`energy-dependent' method of data presentation is equally applicable to any ionisation technique. Breakdown graphs (a plot of percentage fragment ion abundance vs. collision energy or cone voltage) have been used by Harrison and others to obtain energy-resolved fragmentation data from CID experiments at the skimmer cone or in the collision cell of electrospray ionisation mass spectrometers.7 These breakdown graphs represent an alternative way of depicting the same data presented in an EDESI map, and may be incorporated into the EDESI-MS presentation in a logical way by including a breakdown graph on the right-hand side of the map. This approach results in a degree of redundancy, as the data illustrated on the map is projected both onto the mass axis (the summation spectrum at the top of the map) and to the cone (or collision) voltage axis (the breakdown graph at the side of the map). Nonetheless, it does provide an aid to interpretation in much the same way as the standard spectra that are typically projected onto two axes of a...

Energy-Dependent Electrospray Ionization Mass Spectrometry

“…[1]. In simple terms, a spectrum is recorded at each setting of collision energy and the spectra are combined to generate an ion intensity Figure 1.…”

“…EDESI-MS experiments have also been carried out on a number of charged or chemically derivatized compounds, such as transition metal carbonyl clusters, [3] organometallic complexes, [4] and simple organic molecules, [1] although the technique is fully applicable to any sample which undergoes CID. EDESI-MS is also effective for the rapid screening of complex product mixtures.…”

“…Energy-dependent electrospray ionization mass spectrometry (EDESI-MS) provides a simple and effective solution by presenting the information acquired by CID at all voltages in a compact, 2D format. [1] …”

Mechanistic insights from mass spectrometry: examination of the elementary steps of catalytic reactions in the gas phase

“…Such experiments can be conveniently summarized by use of a three-dimensional plot of collision energy vs. m/z, with the intensity of the ion providing the height of the surface (Fig. 3) [18]. This type of presentation is known as "energy-dependent ESI-MS" (EDESI-MS) [19].…”

Gas-phase reactivity of ruthenium carbonyl cluster anions

“…EDESI-MS(/MS) spectra were collected using published procedures [28,29], and processed using the program EDit [30]. The cone gas inlet was spliced to allow the introduction of a reactive gas, either by substituting the nitrogen for another gas or by the simple expedient of allowing the nitrogen to pass through a vial containing a volatile liquid and entraining the vapor of the compound of interest ( Figure 1).…”