Fractional abundance ratios between B213-C2 and five reference sources: TMC-1, B335, B1-b, L1527, and L483. Upper and lower limits are indicated with downward and upward triangles, respectively. L483: Agúndez et al. (2019). TMC-1: Gratier et al. (2016); Cernicharo et al. (2024); Agúndez & Wakelam (2013). L1527: Yoshida et al. (2019). B335: Esplugues et al. (2023). B1-b: Fuente et al. (2016); Loison et al. (2017); Widicus Weaver et al. (2017). N(H₂) values used to obtain fractional abundances are 7.60 × 10²² cm⁻² for B1-b (Daniel et al. 2013), and 1.80 × 10²² cm⁻² for TMC-1 (Palmeirim et al. 2013; Rodríguez-Baras et al. 2021). Physical scales for each source are indicated in the upper left corner.