Fluorous Affinity–Driven Retention of Fluorinated Analytes on a High-Density Fluorinated Silica Gel Stationary Phase

A high-density fluoroalkyl-modified silica gel stationary phase (C10-FSG) was prepared and evaluated as an HPLC stationary phase for fluorinated analytes. Material characterization confirmed the successful formation of a highly fluorinated surface. Compared with nonfluorinated alkyl-bonded silica (C10-SG) and single-modified C10-FSG, the double-modified C10-FSG showed a clearer fluorination-dependent trend for fluorinated aromatic compounds, indicating selectivity distinct from that of a conventional hydrocarbon-bonded phase. Under pure organic mobile-phase conditions, perfluorinated esters were retained much more strongly than their nonfluorinated analogues, showing that strong fluorous affinity can be expressed on the C10-FSG phase even in the absence of water. The retention of PFAS-related carboxylic acids was strongly influenced by the mobile-phase environment. Under strongly acidic, water-rich conditions, medium- and long-chain PFAS acids showed strong retention, while even highly polar short-chain PFAS acids were retained on C10-FSG. Compared with single-modified C10-FSG and a commercial fluorinated stationary phase, double-modified C10-FSG showed stronger retention toward short-chain PFAS acids under the tested conditions. Overall, retention on C10-FSG was governed not only by conventional hydrophobicity, but also by analyte fluorination, solvation, and mobile-phase conditions, providing insight into the chromatographic behavior of PFAS-related analytes on a highly fluorinated stationary phase.