BCECF AM ester is a widely-
used fluorescent indicator for estimating intracellular pH.
1,2 This membrane-
permeant compound is modified by intracellular esterases to produce BCECF, a polar fluorescein derivative that is retained by cells. Intracellular BCECF is stable and has an efflux half-
life of greater than two hours.
3 Intracellular pH measurements are made by ratio imaging, which involves determining the pH-
dependent ratio of emission intensity (detected at 535 nm) when the dye is excited at 490 nm
vs. the emission intensity when excited at 440 nm.
2,4 This approach is amenable to either spectrofluorometry or flow cytometry.
2,5 BCECF AM can also be used to investigate intracellular changes in other ions, including potassium.
6