Figure 20-27 shows the mass spectrum of the same compound from an e1ectronimpact ionization source and an ionization source.

(a) Which mass spectrum would be best for determining the molecular mass of the compound? Why?

(b) Which mass spectrum would be best for determining the chemical structure? Why?

(c) The electron-impact source was a pulsed source used with a TOF mass analyzer. If the flight tube were 1.0 m long and the accelerating voltage were 3000 V. what \would the flight time be for the ion at m/z = 58?

(d) For two ions of m/z values m1/z and m2/z. derive an equation for the difference in flight times. ?tF as a function of the two masses the charges and the accelerating voltage.

(e) For the same Tal' analyzer as in part (c) calculate the difference in flight times between ions of m/z = 59 and m/z = 58.

(f) To get more structural information, the compound of Figure 20-27 was subjected to tandem mass spectrometry. Which ionization source, electron impact or chemical would be most suitable for this purpose? Why?

(g) Using the ionization source chosen in part (f), describe the types of mass spectra that could he obtained from an MS/MS experiment by:

(1) Holding the first mass analyzer constant and scanning the second analyzer.

(2) Scanning both analyzers with a small m/z offset between them.

(3) Scanning the first analyzer while holding the second analyzer constant.

(4) Scanning the second mass analyzer for every mass selected by the first analyzer.
In your answer, use features of the mass spectrum of Figure 20-27 to illustrate your description.