Without calcium and magnesium Phosphate Buffered Saline is used to maintain a physiological pH and osmolarity, two key factors in tissue culture and molecular biology research.  This concentrated form should be diluted to a working concentration using reagent grade water. Without calcium and magnesium Phosphate Buffered Saline is used to maintain a physiological pH and osmolarity, two key factors in tissue culture and molecular biology research.  This concentrated form should be diluted to a working concentration using reagent grade water.