Applications of Arc and Spark Emission Spectroscopy

3 Applications of Arc and Spark Emission Spectroscopy 7.2.3.1 Qualitative Analysis 

Qualitative analysis is performed by recording the emission spectmm of the sample. The sample elements are then identified by comparing their emission spectra with previously recorded spectra from known elements. Generally, for trace amounts, the raies ultimes, or RU lines, must be present and identified in the emission spectra as discussed below. For higher concentrations, the RU lines are present together with many other emission 

Note The roman numerals denote the type of line (atomic, ionic) not the valence state. 

Source Adapted from Thomsen, with permission of ASM International . 

When an element is excited in an electrical discharge, it emits a complex spectrum that consists of many lines, some strong, some weak. When the concentration of the element is decreased, the weaker lines disappear. Upon continuing dilution of the element, more and more lines disappear until only a few are visible. The hnal lines that remain are called the raies ultimes or RU lines, although this term is not used in many modem publications. The RU lines are the most intense emission lines and invariably involve an electronic transition from an excited state to the ground state. These lines can be detected even when small concentrations of the element are present. Conversely, if the element is present in a sample, whatever other spectral lines are emitted from the sample, the RU lines should always be detectable. Some elements and their RU lines are listed in Table 7.11. 

Element Wavelength of RU lines (nm) Element Wavelength of RU lines (nm) Element Wavelength of RU lines (nm) 

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