What is meaning of end capped in HPLC columns?

End capping in HPLC columns refers to the process of chemically modifying the surface of silica particles to block unreacted silanol groups. This is done to reduce unwanted secondary interactions between the analytes and the stationary phase, enhancing column efficiency and improving peak shape. End-capped columns typically provide better reproducibility and selectivity in separation, making them suitable for a wider range of applications.