This analytical method is a validated measurement procedure for the determination of diphenyl ether [101-84-8] in workplace air in a concentration range of one tenth up to twice the currently valid Occupational Exposure Limit Value (OELV) in Germany of 7.1 mg/m³. For sampling, a defined volume of air is drawn through a binder-free quartz fibre filter followed by a silica gel sorbent tube. The flow rate is set to 0.5 l/min and sampling duration is 2 hours (which corresponds to a sampling volume of 60 l). Diphenyl ether is extracted with 2-propanol and subsequently analysed using liquid chromatography with diode array detection. The quantitative determination is based on a calibration function. The limit of quantification is 0.008 mg/m³ based on an air sample volume of 60 l. The mean recovery is 95.3% and the expanded uncertainty for the validation range of 0.71 to 14.2 mg/m³ is 24 to 25%.