3.1 Introduction and History
Greenfield et al. developed plasma-based instruments in the mid 1960s about the same time flame-based instruments such as FAAS and FAES (Chapter 2) became prominent (Analyst, 89, 713-720, 1964). These first plasma-based instruments used direct current (DC) and microwave-induced (MI) systems to generate the plasma. Interference effects and plasma instability limited the utility of plasma instruments during analysis; consequently flame-based spectrometry instruments (such as FAAS) dominated the analytical market for metals analysis and remain effective today.
The limitations of the first plasma instruments were overcome by utilizing an inductively coupled plasma (ICP) instead of DC or MI generated plasma. ICP optical systems became popular in the 1980s due to their decreased cost, lower time investment during analysis, and labor saving advantages. FAAS/FAES instruments require a unique radiation source (lamp) for the approximately 35 elements they can measure. Because the lamp must be changed between each element of interest, FAAS/FAES techniques analyze a single element at a time and are unable to easily analyze metalloids. ICP optical systems, by contrast, can analyze about 60 different elements at the same time with a single source (the plasma). The most common instruments today are inductively coupled plasma—atomic emission spectrometers (ICP-AES) and inductively coupled plasma—mass spectrometers (ICP-MS). ICP-AES will be discussed in this chapter while ICP-MS will be the subject of the next chapter.
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