Abstract: Disclosed are a method of determining the components of a fluoroolefin composition, a method of recharging a fluid system in which the composition is used, and sensors used therefor. In particular, the composition may be a fluoroolefin refrigerant composition used within a vapor compression system, where the refrigerant composition is useful in cooling systems as replacements for existing refrigerants with higher global warming potential. Such fluoroolefin refrigerant compositions have double bond structures which make them particularly well suited with sensing technologies, including: infrared sensors, UV/vis sensors, NIR sensors, ion mobility or plasma chromatographs, gas chromatography, refractometry, mass spectroscopy, high temperature thick film sensors, thin film field effect sensors, pellistor sensors, Taguchi sensors and quartz microbalance sensors.