Calcein

Calcein, AM is widely used for determining cell viability

In living cells the non-fluorescent calcein, AM is hydrolyzed by intracellular esterases into the strongly green fluorescent anion calcein. The fluorescent calcein is well-retained in the cytoplasm in live cells. 

Our UltraPure Grade AM esters of fluorescent indicators are typically at least 95% pure by HPLC analysis.