In order to determine the chemical composition of test pieces, different spectrometers are used.

In spark spectrometers, a spark discharge to the test piece is created with a tungsten cathode, which atomises a small part of the sample surface. These excited atoms radiate light at element-specific wavelengths. The chemical composition of the sample surface can be determined very exactly by the wavelength distribution. Spectrometers are used to monitor the carburizing process exactly or to register material mix-ups, for example.

The glow-discharge spectrometer (GDOES) additionally offers the possibility of determining the elemental distribution up to a depth of 100 µm. This is used particularly when analysing nitriding processes.