Purify it by TLC on silica Gel G (Merck 250a particle size) in two solvent systems (BuOH/AcOH/H2O 30:7.5:12.5 v/v, and BuOH/propionic acid/H2O 30:20:7.5 v/v). When the solvent reaches a height of ~10cm, the plate is removed, dried in air and developed with NH3 vapour giving blue-coloured spots. Also, the dye can be chromatographed on MN Silica Gel with t-BuOH/H2O/n-BuOH (32:10:5 v/v) as eluent and visualised with a dilute KOH (or NaOH if the Na salt is required) spray. The product corresponding to bromosulfalein is scraped off and eluted with H2O, filtered and evaporated to dryness in a vacuum. It was dissolved in H2O and filtered through Sephadex G-25 and evaporated to dryness. [UV and IR identification: Barbier & DeVeerdt J Pharm Sci 57 819 1968, NMR: Kato et al. Chem Pharm Bull Jpn 20 581 1972, McGuire Anal Biochem 83 75 1977, Beilstein 18/9 V 461.]
