The fluorescence of SPQ is specifically quenched by chloride via collision. Therefore, chloride concentration is measured by monitoring the degree of fluorescence decrease. The dye can be loaded into cells by hypotonic shock.    White solid soluble in H2O and DMSO  Store at 4°C. Protect from light, especially in solution.  &lamba; Ex/&lamba; Em = 344nm443nm  ε (344 nm, H2O) = 3,700  C15H15NO4S  MW: 281  [83907-40-8]