Trace Element Analysis 

Trace element analysis within our group is performed by single-collector plasma source mass spectrometry. We have two instruments; a Sector-Field Inductively Coupled Plasma-Mass Spectrometer (SF ICP-MS), and a Quadrupole Inductively Coupled Plasma-Mass Spectrometer (ICP-MS).

The SF ICP-MS (a Thermo Element 2) is arranged with ‘Double Focussing Nier Johnson Geometry’. The magnetic sector field, dispersive for ion momentum is placed before the Electric Static Analyser (ESA), which is dispersive for ion energy. When equal in magnitude but opposite in direction, the energies coupled from the magnet and ESA act to be dispersive to the mass to charge ratio. This forms the basis of the Element 2 mass spectrometer.

This set-up enables the user to analyse many elements to a high resolution (up to R=10,000), thus allowing accurate elemental measurements to be made without many of the problematic isobaric or polymetallic interferences. This is important for many of our research projects, especially those involving the measurements of trace elements in cave calcite samples. Coupled with the high resolution the Element 2 is able to rapidly scan throughout the mass profile of the periodic table. This allows a high frequency of sweeps to be made per sample, which is important towards determining accurate and precise element ratio data.

The Element 2 also provides us with a high performance mass spectrometer in low resolution. When coupled with an Aridus desolvating nebuliser, the instrument is able to detect many elements with a low natural abundance to a high degree of accuracy. An example of such work includes the measurement of the rare earth elements in ocean and sea waters.

 Thermo Element 2

The Quadrupole ICP-MS (a Perkin Elmer Elan 6100 DRC) is a versatile low resolution ICP-MS. Contained within the high vacuum chamber of the instrument, four parallel gold-coated ceramic rods act as a mass filter for the ions that pass into the mass spectrometer. Only ions of a particular mass to charge ratio can pass through the quadrupole and be detected at any one time by the SEM detector. It may not offer the resolution or performance of the Element 2, but instead provides a dynamic linear working range, which is useful for chemistry tests or for screening of unknown or new samples.  

Quadrupole ICPMSPerkin Elmer Elan 6100DRC