Sampling interface design and function

If the response versus mass of a typical modern ICP-MS is considered under normal operating conditions, then for most if not all commercial instruments (quadrupole, time of flight and magnetic sector), sensitivity increases with mass. Therefore, for example, 1 ng/mL of is found to yield a larger signal than 1 ng/mL of Li. However, when one considers this in terms of the actual number of atoms in the solution, then in the case of the 1 ng/mL of Li and U example, there are 238/7 times more Li atoms in that solution than there are atoms, since 7 g of Li contains 

The quadrupole mass filter is probably the most robust type of mass analyser, being capable of operating at relatively high pressures, approaching 10 mbar. So it was unsurprising that all early interface development focused on using quadrupole mass filters, rather than magnetic 

Additional discussions on the physics of the plasma sampling interface can he found in the literature. This continues to be a dynamic research field and considerable advances remain to be made given the high loss of analyte ions between the ICP source and the mass spectrometer. 

Inductively Coupled Plasma Mass Spectrometry Handbook 

This region of free expansion is called the zone of silence. Spaced behind the sample cone is a second cone with a smaller orifice in its tip (0.4-0.7 mm), called the skimmer cone. For the skimmer cone to sample the expanding plasma gas effectively, the orifice must be situated 

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