HILIC-like separation on a base-deactivated C₁₈ column for ion-pair-free LC-MS/MS analysis of 16 aminoglycosides in...

An LC-MS/MS method was developed for the simultaneous determination of 16 aminoglycosides (AGs) in pork, chicken, milk, and eggs using a conventional Hypersil base-deactivated silica (BDS) C₁₈ column operated under HILIC-like conditions. Unlike typical C₁₈-based methods that rely on ion-pairing reagents in the LC mobile phase, separation was achieved with an ion-pair-free mobile phase consisting only of 0.1% formic acid and acetonitrile under gradient elution. Column comparison, aqueous-fraction experiments, and SRM 870 probe testing indicated a mixed retention mechanism involving hydrophilic partitioning into a water-enriched interfacial layer and reversible interactions with accessible residual silanol sites. Because the method prioritizes MS compatibility and reproducible multi-residue quantification, compound-specific MRM transitions and matrix-matched calibration were used to ensure selectivity and quantitative reliability. The method showed good linearity (R² > 0.99), satisfactory accuracy (71.2-99.8%) with reported standard deviations, acceptable precision (CV ≤ 11.3%), and low detection limits (LODs 3-15 μg/kg; LOQs 10-50 μg/kg). Overall, this work demonstrates that a conventional C₁₈ column can exhibit pronounced hydrophilic selectivity under high-organic conditions, offering a practical, MS-friendly alternative for aminoglycoside residue analysis and informing future stationary-phase development for hydrophilic separations.