The Missing Link for Efficient Supercritical Fluid Extraction: A Unified Theory of Solvation Shell Dynamics, Intermolecular Forces, and Pressure-Selective Extraction Windows

Background: Supercritical fluid extraction (SFE) has been extensively studied and applied across pharmaceuticals, food processing, and environmental remediation. However, a fundamental disconnect persists between the phenomenological optimization approaches dominant in the literature and the underlying molecular mechanisms governing extraction efficiency. Methods: This work synthesizes evidence from molecular dynamics simulations, thermodynamic measurements, chromatographic studies, and extraction experiments across multiple disciplines to develop a unified theoretical framework. We analyze coordination number variations, local density augmentation phenomena, dielectric constant tunability, and interfacial tension effects as interconnected parameters. Results: We demonstrate that extraction efficiency exhibits non-monotonic dependence on pressure, with distinct "optimal windows" occurring where the number of solvent molecules in the first solvation shell reaches its maximum. This coordination number maximum (CN ) max occurs within narrow pressure-temperature ranges specific to each solute-solvent system. Conclusions: We propose a new paradigm of pressure-selective extraction based on solvation shell optimization, introducing the concept of cyclic pressure gradient extraction (CPGE) as a methodology for maximizing extraction efficiency of complex mixtures.