Secondly, lucigenin also has a significantly higher extinction coefficient than SPQ with a similar quantum yield (0.67), which thus leads to higher emission intensities. Another limitation of quinolinium probes is that the excitation wavelength for SPQ is in the UV range (322 and 350 nm), where the scattering by the liposomes (with diameters of 130-200 nm) results in less efficient excitation. The use of the additional excitation band of lucigenin at 430 nm mitigates this issue.