Optical emission spectrometry (ICP-OES) and mass spectrometry (ICP-MS), both with inductively coupled plasma, have today become one of the most versatile and powerful analytical methods for qualitative and quantitative element analysis.
The two perfectly complementary methods together cover the largest area of main, secondary, and trace element determination. They have evolved to become the leading technology for routine and special analysis and are indispensable in the fields of environmental analysis, modern material and substance analysis, in-process and contamination analysis as well as quality assurance and research.
The analytical methods based on inductively coupled plasmas are capable of supplying the quantitative element composition for a variety of sample types, such as liquids, suspensions, solids, powders, etc. In the case of solid samples, a dissolving process, melting digestion or microwave-supported acid digestion is usually necessary in which potentially volatile analytes are preserved in the digestion solution.
The sample solution is converted into a fine aerosol by atomizer which is then introduced into an inductively coupled argon plasma (ICP) at temperatures of 6,000–10,000 K. Here, the solution goes through the following processes:
Drying → Desolvation → Evaporation → Atomization → Ionization
ICP-OES: Due to the high temperatures in the plasma, the analyte atoms and ions are thermally stimulated and emit light of their characteristic wavelengths. In the spectrometer, the radiation emitted by specific elements is separated by wavelength by means of diffraction grids (Echelle grids), amplified and measured simultaneously by means of a semiconductor detector. Quantification is carried out using calibration standards. ICP-OES is particularly suitable for ppm analysis.
ICP-MS: In contrast to OES, ICP-MS analyzes the masses of the ions produced in the plasma. The analytes present in the sample are fed as simply charged ions to a quadrupole mass spectrometer and separated, amplified and sequentially detected according to their mass/charge ratio. ICP-MS offers an extremely high degree of sensitivity to a wide variety of elements and is particularly powerful in trace analysis (ppb/ppt).
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