Laser ablation inductively coupled mass spectrometry (LA- ICP-MS) is an analytical technique capable of quantitative, in situ, trace and ultra-trace analysis with high spatial resolution. The technique combines direct sampling of solids, via the heating action of a focused laser, and mass spectrometric determination. Particles ablated from the sample surface are transported in a stream of argon gas to an inductively coupled argon plasma where they are vaporized, dissociated and ionized. The ions, dominated by singly charged species, are extracted from the plasma through a set of differentially pumped orifices and separated, based on their mass to charge ratio, using a quadrupole mass spectrometer. All elements except fluorine can be detected; however most gaseous elements cannot be quantified because of entrapment of air in the argon plasma. The technique is useful for all other elements from mass 6 (Li) through mass 238 (U).

Infrared and ultraviolet laser sources are used to address geochemical problems. Infrared lasers typically operate at 1064 nm and high power (500 mJoule/pulse), and ultraviolet lasers typically operate at a frequency-quadrupled wavelength of 266nm. Commercial infrared lasers are best suited for studies where spatial resolution and sample integrity are less important than spectral sensitivity. Ultraviolet lasers and beam attenuated infrared lasers provide high spatial resolution (commonly 10 microns or less) and less sample damage with some sacrifice of sensitivity.

Suitable sample preparation to produce a homogeneous glass, e.g. using a lithium borate fusion, allows bulk analysis of rocks. This has the advantage of precise determination for a wide variety of trace elements that otherwise would require several independent techniques. However, the power of the technique for geochemical analysis lies in its capability as a trace element microprobe, e.g., for mineral analysis, where the spatial context can be preserved. The ultimate aim is to produce precise analytical data from thin sections, but this has yet to be realized on a routine basis. Studies to date on silicates, carbonates and a variety of other minerals indicate that methods for geologic application can be developed for this technique.