Fig. 3. (a) Iron(iii) adsorption by PAF-1–ET measured by ICP-MS in 100 mM HEPES (pH = 6.7) aqueous solutions using FeCl₃ as the iron(iii) source. (b) Absorption spectra resulting from the addition of a 1 mM aqueous solution of 8-hydroxyquinoline to dried PAF-1–ET, obtained after exposure to the iron(iii) aqueous solutions shown in (a). The top red spectrum corresponds to the absorption of a complex of iron(iii) and 8-hydroxyquinoline, and the gray absorption spectra with increasing absorbance at 460 nm correspond to the solutions in (a) with increasing initial concentrations of iron(iii). (c) A close correlation was observed between the iron(iii) uptake measured by ICP-MS (gray squares) and the iron(iii) uptake obtained from the absorbance at 460 nm in the presence of the 8-hydroxyquinoline indicator (open circles).