Inductively Coupled Plasma-Mass Spectrometer (ICP-MS)

Technique in brief

ICP-MS is a fast and sensitive technique for multi-element analysis. Samples are introduced as a solution or via laser ablation to a plasma, the temperature of which effectively converts the elements present to ions. The ions produced will have differing mass and charge depending upon the element from which they are produced and these may be separated using a mass spectrometer. This essentially works as a filter only allowing positive ions of a particular mass to charge ratio pass through to a detector at any one time. Although the instrument is measuring sequentially (one mass/charge at a time), it does so at a very fast rate, with the result that for most applications it can be considered as "simultaneous" acquisition.

Current instrumentation

The AAC current operates two Varian ICP-MS 820 series instruments. Both instruments are configured to be able to be used with either solution-based samples or analysis of solids via laser ablation.

Applications

ICP-MS provides quantitative analysis for a large part of the elements of the periodic table and is particularly suitable for trace and ultra-trace levels (equivalent to parts per million to sub-parts per billion). It should be noted however that elements that prefer to form negative ions (ie F, Cl, I) cannot be analysed by this method. The technique can be applied to the determination of elemental composition of a wide variety of material types including geological, environmental, biological.

Sample requirements

Samples for ICP-MS can be introduced as a solution (a liquid phase) or by laser ablation. Where bulk/whole or acid soluble analysis is required of solid samples the material needs to be crushed and dried and a suitable method employed to dissolve the material (normally accomplished by open vessel or microwave-assisted digestion in acids or, where necessary by fusion techniques). In most instances the AAC will perform sample digestion.

Laser ablation material is typically mounted on glass slides or in epoxy resin mounts. These are then cut and polished prior to ablation.

For further information contact the officer in charge:

Dr Yi Hu