Open solvent bottles sitting on top of HPLC machines leak vapors. Over time as chemicals evaporate concentrations change inside the bottle and that can affect chromatography results. What’s more, open solvent bottles can leak toxic, flammable vapors into the air people breathe. Trying to seal the bottles with foil or parafilm doesn’t help. Finally, if the bottles get knocked over the fumes get worse.  
 
Reagent bottle caps from Argento Scientific provide these features:

• Ensures reagent bottles are sealed

• Caps include integrated PTFE filters - the entering air is filtered so not contaminated

• Caps contain duck-bill check valves - prevent spills even if the bottles are knocked over

• Secure tubes in place

• Prevent pumps from cavitating

• Block vapors from evaporating (to preserve concentrations)