a) A classic German mass analyzer design – in fact the first double focusing geometry of magnetic sector instruments – is still used for a certain method in inorganic MS. Can you name the analyzer and the method? Why is this analyzer important for the technique?
The famous Mattauch-Herzog geometry (Chap. 4) offers a detection plane for simultaneous ion detection, e.g., on photographic plates. Thus, the m/z range of interest can be recorded without affecting the signal intensity by fluctuating ion production from the source. SS-MS has high fluctation in ion flux, and moreover, delivers ions having a large kinetic energy spread that needs to be compensated by the electrostatic sector (Chap. 15).
b) ICP-MS has become widespread in inorganic MS. The plasma torch is constructed of three coaxial tubes surrounded by the RF load coil.
1. Explain the function of each of these tubes.
The sample aerosol is admitted via the central line. The intermediate tube delivers a stream of argon to form the plasma. The outer tube creates a laminar argon sheath flow around the plasma to prevent the instrument from damage by the hot plasma.
2. What is the material they are made of?
Fused silica, because it is rather inert and resistive to heat.
3. Specify the temperature range of the ICP.
The plasma can reach 10,000 K in the center between the coils and still has 5000-6000 K at the sampling orifice.
c) What do you know about the ionization efficiency in TIMS?
1. How does it depend on the temperature of the filament?
Increasing temperature improves thermal ionization efficiency, which is described by the Saha-Langmuir equation (Chap. 15.1).
2. Is it independent of the element to be analyzed?
No. Each element has a thermal ionization efficiency of its on. Low ionization energy of the element results in higher thermal ionization effeciency at given temperature.
3. Is it independent of the material of the metal ribbon?
No, Re has a higher work function than W, and thus, yields better thermal ionization efficiency at given temperature and analyte.