Glow Discharge Mass Spectrometry (GDMS)

Take Home Point:

Survey trace/ultra-trace elemental analysis of metals/alloys, ceramics and inorganic powders

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What It Provides:

Provides concentration tables of low/ultra-trace level components and impurities present in solid samples.  It can also provide concentration versus depth of these species via depth profiles at both small and relatively large depths. 

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Brief Description:

 

Argon Ions In/Ions Out

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GDMS is good choice when trace and ultra-trace level detection of elements in samples is needed.  Additionally, it is a survey technique meaning that one doesn't need to know which elements to sample prior to analysis. 

 

In GDMS the sample is subjected to a plasma (typically Argon) that causes the 'atomization' (i.e. sputtering as atoms) of the sample surface.  The plasma consists of electrons and positive Argon ions, the latter which are accelerated to the sample surface resulting in sputtering.  These sputtered atoms are subsequently ionized by other Ar ions within the plasma.  Since atomization and ionization are separate events, the technique has minimal matrix effects allowing for the use of standard Relative Sensitivity Factors (RSFs).  Following ionization, the metals ions are accelerated into a mass spectrometer for mass separation and detection.  

 

While GDMS is commonly used to provide 'bulk' analysis, it can also be used for depth profiling.  Some characteristics that make it well suited for the latter is it can have nm depth resolution, fast sputter rates, survey capability, excellent sensitivity and low matrix effects.