What is ICPMS and laser ablation

ICPMS (Inductively Coupled Plasma Mass Spectrometer) is an analytical instrument that is capable of detecting the isotopic composition and the trace concentrations of elements present in the sample. The samples are introduced either as solutions in the form of a fine aerosol in Ar or Ar-He gas mixture (solution ICPMS) or, alternatively, solid materials can be sampled directly (in situ) using Laser Ablation. The fine aerosol from the solution, or the ablated material from the laser sampling, enters the RF-generated argon plasma (temperatures up to 10 000 K) where virtually all atoms and molecules are converted to ions before they enter the high vacuum stage of the mass spectrometer through a small entrance hole in the interface. The ions are accelerated and focused into an ion beam by a series of electrostatic lenses. The ion beam is then analysed by a fast switching mass filter - the quadrupole. The mass filter selects particles on the basis of their mass/charge ratio so that only specific isotopes are allowed through the filter and can enter the electron multiplier detector mounted at the end of the quadrupole. Fast switching of the quadrupole settings enables scanning or peak jumping over the mass spectrum. Detected signals of individual isotopes can be converted to isotopic ratios or, when standards are measured along with the unknowns, to the element concentrations.

Schematics of inductively coupled plasma mass spectrometer (VG PlasmaQuad 3).

Schematics of the laser ablation system.

For a more thorough introduction to the technique see Yann Lahaye's lecture on ICPMS and laser ablation. Further comprehensive information on the technique can be found e.g. in "Inductively Coupled Plasma Mass Spectrometry" edited by Akbar Montaser (Wiley-VCH, 1998).