Mass-Analyzed Ion Kinetic Energy Spectra

Certain quinazolines, e,g. l-methylquinazolin-4(l//)-one, fragment by a retro-Diels-Alder process. The MIKE (mass analyzed ion kinetic energy) spectrum of the molecular dication of quinazoline is very similar to that of quinoxaline. MIKE spectra of quinazolinethiones show the loss of NCS radicals from the molecular ionA ... 

Figure 16, Top — Mass-analyzed ion kinetic energy spectrum (MIKES) of the precursor ion CeoFTe acquired at 10 keV collisons energy with the collision gas. Bottom — the intensity ratio of the product dianion (CeoFTe) to the monoanion precursor (CeoFTe) as a function of collision energy.

Mass-analyzed ion kinetic energy spectroscopy (MIKES). This scan is implemented with reverse-geometry (BE-type) instruments, in which the front-end magnetic sector allows exclusive mass selection of a precursor ion [37], Fragmentation occurs in a region between the two analyzers (second FFR). A scan of the electric sector [Eq. (4.12)] yields a product-ion spectrum. MIKES also allows direct measmement of kinetic-energy release values. 

The MC-ICP-MS consists of four main parts 1) a sample introduction system that inlets the sample into the instrument as either a liquid (most common), gas, or solid (e.g., laser ablation), 2) an inductively coupled Ar plasma in which the sample is evaporated, vaporized, atomized, and ionized, 3) an ion transfer mechanism (the mass spectrometer interface) that separates the atmospheric pressure of the plasma from the vacuum of the analyzer, and 4) a mass analyzer that deals with the ion kinetic energy spread and produces a mass spectrum with flat topped peaks suitable for isotope ratio measurements. 

A time-of-flight spectrometer can be used as a mass analyzer, an ion kinetic energy analyzer, and an ion reaction time analyzer. We will consider here only what factors affect the resolution of the system in mass analysis.74 The same consideration can easily be extended to find the resolution in other analyses. There are at least two kinds of mass resolution. One refers to the ability of the system to separate two ion species of nearly equal masses in the same mass spectrum. This is related to the sharpness of the mass lines, or the full width at half maximum (FWHM) of the mass lines. The other refers to the ability of the system to distinguish two ion species of nearly identical masses, but not necessarily in the same mass spectrum. This latter mass resolution is related to the sharpness of reference points in the mass lines such as the onset flight times of the ion species, and the overall long-term stability of the system. This latter resolution determined also how accurately the instrument can measure the mass of ion species. Although this latter resolution is more closely related to ion kinetic energy analysis and is as important as the former one, we will consider here only the former kind, or the conventional kind, of mass resolution. 

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