Fig. 2

Mass spectrometric analysis of the rhein hydrogel. a, b MS analyses of the rhein hydrogel. c MS/MS analyses of monomer [M−H]⁻. d MS/MS analyses of dimer [2M−2H+Na]⁻. e MS/MS analyses of trimer [3M−3H+2Na]⁻. f MS/MS analyses of tetramer [4M−4H+3Na]⁻. g MS/MS analyses of pentamer [5M−5H+4Na]⁻