Comparison of the column densities of the CN-bearing molecular family with HCO⁺. The blacksymbols correspond to the absorption study against Galactic star-forming regions by Godard et al. (2010), the blue symbols correspond to the absorption study against quasars by Lucas & Liszt (2000a), and the red symbols refer to this work. We also include in green symbols the recent work by Ando et al. (2016) using Galactic ALMA calibrators and in yellow the absorption line study of a z = 0.89 galaxy by Muller et al. (2011).