This second in a blog series on robustness and its role in enhancing lab optimization processes focused on inductively coupled plasma mass spectrometry (ICP-MS). The series takes a critical look at the term “robustness” and describes how it relates to a portfolio of analytical instruments (hardware and software) in quantifiable terms and benefits. The working definition for robustness (described in Part 1 of the series) includes three aspects: measurement, instrument, and process.
What is an RF generator?
The following describes an example of instrument robustness that centers on radio frequency (RF) generator technology -- a critical component used in the detection of trace metals by ICP-OES and ICP-MS. Briefly, ICP-OES and ICP-MS instruments utilize high purity argon and an oscillating radio frequency field to generate and sustain a plasma which is used as an atomization and ionization source during analysis. In this setup, a constant stream of argon flows through a torch that is positioned inside a load coil. A high frequency field is applied to the load coil. A high voltage spark is applied to the torch, stripping some of the argon atoms of their outer electrons. Those ionized argon atoms are accelerated through the load coil, causing them to collide with other argon atoms and to be stripped of their outer electrons. This process repeats until a stable plasma is formed.
What is the value of an RF generator?
A robust RF generator will continually sustain a plasma and allow it to fully desolvate, vaporize, atomize and ionize liquid samples. A key challenge is for the RF generator is its ability to adjust for changing conditions in the plasma (due to differing sample matrices, such as high metal or salt content and organic solutions). Rapid changes in plasma conditions require an RF generator which will quickly respond to changes and achieve a stable plasma as quickly as possible.
The following provides an example of a robustness study showing excellent stability (within <2 RSD over an 8 hour period) using the iCAP 7000 Plus Series ICP-OES RF generator. The solution used was a continuously aspirated 50 g/L Ni solution spiked with various concentrations of elements and the intensities plotted as a percentage.
The Thermo ScientificTM iCAPTM RQ ICP-MS with new solid state RF generator plus hot and cold plasma operation provides the additional robustness benefit of enhanced uptime and low maintenance.