Inductively Coupled Plasma-Mass Spectrometry (ICP-MS)

Take Home Point:

Trace elemental analysis of liquid and solid samples  

​

What It Provides:

Provides concentration tables of low/trace level components and impurities present in liquid and solid samples (after digestion).

​

Brief Description:

 

Sample into Plasma/Ions Out

​

In ICP-MS samples are first ionized by the inductively coupled plasma (ICP) and then analyzed by the mass spectrometer (MS). Preparation of the samples typically involves digestion with acidic solutions and sometimes heat.  Microwave digestion is also used.  The samples are then reconstituted in a slightly acidic aqueous matrix for analysis.  Liquids can be analyzed directly assuming that the total dissolved solid levels is less than ~0.5%.  

 

The prepared liquids are introduced into the instrument using a nebulizer that converts it into a fine mist and then carries it into a spray chamber with a stream of gas to remove large droplets.  The mist next enters a 'torch' which mixes the sample with additional gas flow before entering the plasma (typically Ar).  Within the plasma the sample separates into individual atoms due to the extremely high temps and the atoms are subsequently ionized.  

 

The gas containing the ions then flows through a set of cones that removes much of the Ar gas before the ions enter the vacuum of the mass spectrometer for mass selection and detection.    

 

ICP-MS is similar to ICP-OES except that in the latter detection is based on measuring the wavelength of light emitted by the sample.  ICP-MS is more sensitive and has less interferences while ICP-OES is more robust.   ICP-OES is better for 'dirty' samples with high levels of suspended and/or dissolved solids where ICP-MS samples should be relatively clean.