7. The most favorable ratio of 29 is observed for B2, meaning that the absorbance of B2 at 422 nm is 29 times stronger than that of G1 at the same wavelength. From a chemical point-of-view B2 is also preferred over B1, since the two methyl groups replace two fairly acidic protons next to the NBF2Nunit, which renders B1 (and derivatives) base-sensitive. 19.5@413 nm 28.9@422 nm 24.2@426 nm 12.5@431 nm Fig. . Absorption spectra of B1, B2, B3, B4 and the green dye G1. The numbers on top of the peaks denote the ratio of the absorption of B1, B2, B3 and B4, respectively, relative to the absorbance of G1 at the given wavelengths (c= 2.0 • 10 -6 mol/L).