HBS-EP is a ready-to-use HEPES-buffered saline of 10 mM HEPES, 150 mM sodium chloride, 3 mM EDTA, and 0.005% polysorbate 20 (Tween-20) in purified water. The 200 mL fill suits bench-scale instrument runs.

It is commonly used as the running buffer for surface plasmon resonance (SPR) binding and kinetics studies of proteins, antibodies, and other biomolecules. EDTA chelates divalent cations, and the surfactant reduces nonspecific binding to the sensor surface. Filter and degas before use.