2,7-BIS-(2-CARBOXYETHYL 1 MG，B1150，Invitrogen

With a pK_a of ~6.98, the cell-permeant, dual-excitation ratiometric pH indicator BCECF, AM is ideal for measuring changes in the cytosolic pH of most cells. Intracellular pH measurements with BCECF are made by determining the pH-dependent ratio of emission intensity (detected at 535 nm) when the dye is excited at ~490 nm versus the emission intensity when excited at its isobestic point of ~440 nm.