5-(and-6)-carboxy-2',7'-dichlorofluorescein is similar to carboxyfluorescein, but has lower pKa. It is useful for detecting pH in more acidic environment. Also see the membrane-permeant compound dichlorofluorescein diacetate.
pKa = 4.8
&lamba;Ex/&lamba;Em = 504/529 nm
ε= 90,000
Orange solid soluble in DMSO and pH>6 buffers
Store at room temperature and protect from light, especially in solution