Table 2. UV absorption bands for chromophores, adapted from [29].

Chromophore	Formula	Wavelength nm (ε at maximum)*	Relation to RNA samples
Amine	–NH2	195 (3000)	Present in purines/pyrimidines, e.g. the nitrogenous bases.
Ester	O = C–O–C	205 (50)	Substitution of Carbon with Phosphor creates the phosphodiester bond (O = P–O–C), which forms the linkage between nucleotides.
Carboxyl	O = C–O–H	205 (60)	Present in amino acids, which may contaminate RNA isolations.

*The extinction coefficient ε  =  M_r.(A/cl), and is related to the relative molecular mass, M_r.