Atomic-emission spectrometry with inductively coupled plasma ICP-AES, see also Chapter

12 Atomic-emission spectrometry with inductively coupled plasma (ICP-AES, see also Chapter 2) 

ICP-AES is a technique of measurement used for the detection and determination of elements with the aid of atomic emission. The solution for measurement is atomized and the aerosol is transported into an inductively coupled plasma (ICP) with the aid of a carrier gas. There, the elements are excited such that they emit radiation. This is spectrally dispersed in a spectrometer and the intensities of the emitted element lines are measured by means of detectors (photomultipliers). A quantitative statement is possible by means of calibration with reference solutions, there being a linear relationship between the intensities of the emission lines and the concentrations of the elements over a broad range (usually several powers of ten). The elements may be determined either simultaneously or consecutively. 

Basically, ICP-AES is a low-interference method. In individual cases, however, the spectral and non-spectral types of interference described below may occur. Of these, line coincidences and interference due to sample feeding are the most significant in practice. 

This interference arises as a result of overlapping of the spectral lines. Line coincidences become apparent only when a critical concentration ratio between the interfering and analyzed elements is reached. They are dependent on the spectral resolution of the spectrometer. The line coincidences which may occur in the analysis of wastewater have been established in a test. The results of this test are summarized in Table b. 

Molecules or radicals (e.g N2+, OH, NO, CN and NH), which are formed in the plasma from the solvent, the surrounding air, the gases used or incompletely dissociated compounds, (e.g. AlO), may emit bands which coincide with the lines under analysis. 

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