What are the main differences between Earle's BSS and Hank's BSS? 


A balanced salt solution (BSS) is a solution made to a physiological pH and salt concentration.  Solutions most commonly include sodium, potassium, calcium, magnesium, and chloride.   Balanced salt solutions are used for washing tissues and cells and are usually combined with other agents to treat the tissues and cells. They provide the cells with water and inorganic ions, while maintaining a physiological pH and osmotic pressure.

Sometimes glucose is added as an energy source and phenol red is used as a pH indicator.


Intended to equilibrate with air in a closed system that contains a low concentration of sodium bicarbonate.


Intended to equilibrate with a gaseous phase containing 5% CO2 and contains a higher concentration of sodium bicarbonate in the solution.  Has superior buffering abilogy because it contains a greater amount of sodium bicarbonate, although it is more difficult to use because it requires a special gaseous mixture of 5% CO2 to 95% air, supplied above the culture medium.  If this procedure is not followed, the pH rapidly increases and cell growth is inhibited at normal incubation temperature.  Another related method is to use a medium that produces adequate buffering capacity but does not require the 5% CO2 to 95% air mixture to be added to the environment above the culture medium.  In some cases this can be achieved by using a medium containing Earle’s salts with the sodium bicarbonate concentration reduced to 0.85g/L.

The main difference between Earle’s and Hanks is the sodium bicarbonate level. Earle’s has a higher sodium bicarbonate level so it needs to be used in a 5% CO2 air environment. Hank’s has a lower sodium bicarbonate level so it is more used in a closed system. However the customer would need to know which one they need for their experiment. Balanced salt solutions are used to wash tissues and as a way to keep medium at a certain physiological pH and salt concentration.

In terms of alpha EMEM and EMEM. EMEM was developed first and was mainly designed for HeLa and L cells. It has a higher concentration of nutrients so there are longer periods of time between feedings. EMEM has 2-5X greater vitamin concentrations, and higher concentrations of amino acids then BME. Alpha EMEM was developed to contain a unique set of components that other MEM medias to do not have. Some of those components are Vitamin B12, ascorbic acid, lipoic acid, sodium pyruvate and D-Biotin.

Classical Media and Reagents