Abstract: The invention relates to a method for the determination of impurities in silicon, in which a monocrystalline rod is produced by means of zone refining from a silicon to be tested; this monocrystalline rod is introduced, in at least one dilution step, into a casing made of mono- or polycrystalline silicon having defined carbon and dopant concentrations and a diluted monocrystalline rod of silicon is produced from the rod and casing by means of zone refining; wherein the determination of impurities in the silicon to be tested is carried out with the aid of a diluted monocrystalline rod by means of photoluminescence or FTIR or both.