For the determination of phosphorus, the sample to be analyzed is converted into an analyzable solution by using high-purity reagents. Depending on the sample matrix and the expected phosphorus content, different digestion systems are available. The detection is performed by optical emission spectrometry with an inductively coupled plasma (ICP-AES). The digestion solution is transported into an argon plasma after nebulisation and the phosphorus atoms are excited to emit light. The wavelength of the emitted light is element-specific and is detected after spectral decomposition within a polychromator by using CID-technology.