icp

Categories

• ICP (Inductively Coupled Plasma) - this is a high temperature plasma (partly ionised argon) sustained with a radiofrequency electric current, which acts to produce ions. The electric current is transferred to the plasma by an induction coil, wrapped around a configuration of concentric quartz tubes (the plasma torch). The common operating frequencies are 27.12 and 40.68 MHz and operating power is in the range between 800 and 1500 W. The plasma is sustained within a constant flow of argon gas, open to atmosphere and reaches temperatures as high as 10,000 K in the hottest part. To prevent melting of the torch a high flow rate of argon is used in the outermost tubing. The total gas consumption of a typical analytical ICP is in the range of 14 - 18 L/min. In order to reduce capacititive coupling between the coil and plasma, some designs employ an additional metal sheet between the torch body and the induction coil.

• MS (Mass Spectrometry) the ions from the plasma are extracted through a series of cones into a mass spectrometer, usually a quadrupole. The ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration.

The concentration of a sample can be determined through calibration with elemental standards. ICP-MS also lends itself to quantitative determinations through isotope dilution, a single point method based on an isotopically enriched standard.

Other mass analyzers coupled to ICP systems include double focusing magnetic-electrostatic sector systems with both single and multiple collector, as well as time of flight systems (both with axial and orthogonal accelerators).

Another type of spectrometer using ICP is ICP-AES (Atomic Emission Spectrometer).

There is an increasing trend of using ICP-MS as a tool in Speciation Analysis, which normally involves a front end chromatograph separation and an elemental selective detector, such as AAS and ICP-MS.