“…S2a-d, ESI †) to obtain the liquid-ice/hydrate mixture where the liquid phase is the FCE. Finally, extract the FCE from the liquid-ice/hydrate mixture by syringe-filtration method and determine its concentration via refractive index method 26 (for single-solute systems), or analytical chemistry techniques such as inductively coupled plasma atomic emission spectrometry (ICP-AES), 27 ion chromatography, 28,29 and so on.…”