Petroleum hydrocarbons analyzer AE-2 is designed for continuous automatic monitoring of content of petroleum hydrocarbons in potable, natural, and waste water. The instrument comprises a sample preparation unit and a fluorescence detector. The sample preparation unit provides metered water feed and switching of the water and reagent flows, control of temperature, mixing and mass-exchange processes. The detector (or optical cell) performs the detection of fluorescence of petroleum hydrocarbons extracted by hexane from the sample using a patented chromato membrane technology.