BCECF, AM is an ideal cell-permeant, dual-excitation ratiometric pH indicator 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. This dye is provided as 1 mg solid (C028) and 1 mg/mL solution in DMSO (C029).