Most labs use this bottle cap to ensure that their mobile phase is not contaminated and thereby helps to comply with their HPLC GLP requirements

Your mobile phase will only contact medical grade PTFE so there will not be any contamination from plastic or wax film. Keeping these caps on the bottles with the tubing through holes prevents dust and dirt from getting in and minimizes outgassing or absorption of CO2 from the atmosphere. The cap assembly can be autoclaved.