In the current study, we have developed a green water switchable liquid–liquid microextraction method for separation, preconcentration, and estimation of selenium concentration in the real samples. First time introducing the water switchable liquid–liquid microextraction method to determine the trace level selenium in different food and soft drink samples. Water switchable medium was formed by the reaction of diethylenetriamine base when exposed to uniformed pressure of carbon dioxide. After being exposed to carbon dioxide, water switchable medium reversibly exchanges in two separated aqueous and organic phases. Advantages of carbon dioxide uses are cheap, environmental friendly, non-accumulation, removable, and require the opaque materials for operating container. Water switchable phenomena occurred easily from low polarity to high polarity organic solvent. Experimental variables of the water switchable liquid–liquid microextraction (LLME) method were optimized into its optimum values such as pressure, pH, centrifugation speed, extraction time, and concentration of complexing agent. The certified reference material of Canada Lake Water (TMDA-53.3) and CS-M-3 Mushroom ( Boletus edulis ) was used for validation of the present water switchable LLME method. Enhancement factor and limit of detection were obtained 85.5 and 0.018 μg kg −1 , respectively. Developed green water switchable LLME method was successfully applied for assessment of total selenium in tomato, pumpkin seed, mushroom, garlic, rice, pistachio, chickpea, hazelnut, walnut, apple juice, and ice tea samples.