Question

1)With the aid of a diagram, describe the functions of an electron
ionization source for mass spectrometer used in atomic mass spectrometry.

2) What are the functions of the ionising and accelerating chambers in a mass
spectrometer?

3) Briefly, but informatively, describe a time of flight (ToF) mass spectrometer. What do you
think are the advantages and limitations of ToF over Qaudrupole mass analysers?

Answer 1

1.The functions of an electron ionisation source for mass spectrometer is that it generates fast moving electrons which interacts with the sample to produce ions.

2. Functions of ionising and accelerating chambers in a mass spectrometer is to ionise the sample either cation or anion as per the detection mode and to accelerate the produced ions so that the ions can reach to the detector.

3.Time of flight(TOF) mass spectrometer is a spectrometer in which the m/z ie mass by charge ratio is determined by measuring time. An electric field of known strength is used for accelerating the ions. All the ions get equal kinetic energy(1/2mV^2). So ions with smaller m gets more velocity and so lesser time of flight.

Advantages of TOF over Qaudrupole mass analysers are faster data acquisition(ie shorter scan time) without sacrificing the sensitivity, spectral continuity and exceptional dynamic range.

Limitations of TOF over Qaudrupole mass analyser is that it's costly as compared to Qaudrupole mass analyser and both qualitative and quantitative mass analysis can't be done in TOF unlike Qaudrupole mass analyser.