RPMI 1640 medium is a general purpose medium based on the RPMI 1630 line of media which utilized a bicarbonate buffering system and alterations in the amounts of amino acids and vitamins. A Dutch Modification of RPMI 1640 is also available through MP. The Dutch Modification contains 6400 mg/L sodium chloride instead of 6000 mg/L; contains 1000 mg/L sodium bicarbonate instead of 2000 mg/L; and contains 20 mM HEPES.