The method consists in analyzing a small quantity of essential oil on a column of small diameter but great length under specified conditions. The citral content is determined by using the internal standard method. Polyethylene glycol 20000 is used as stationary phase. Operating temperatures: Oven: linear temperature programming from 80 to 180 °C at a rate of 2 °C/min. Injection system: about 190 to 200 °C. Detector: 200 to 250 °C, maximum.