A method and system for determining a density of a fluid is provided. The method is carried out using an electrospraying apparatus connected in the system. At a first step fluid is introduced into an emitter of the electrospraying apparatus. A voltage is applied between the emitter and a counter-electrode spaced apart from the emitter for a number of intermittent time periods, wherein the duration of at least some of the time periods during which the voltage is applied progressively decreases. The current between the emitter and the counter-electrode is measured for each time period during which a voltage is applied and the shortest time period for which a current reading is obtained is recorded. The shortest time period is used to calculate the density of the fluid in the emitter.