On the chromatographic behavior of dipicolinic acid

Summary Paper chromatography of 100g or more of dipicolinic acid (DPA) in acetic acid-containing solvents resulted in 3 distinct ultraviolet-absorbing sports at different R_f values. The ultraviolet absorption spectra of eluates of the respective spots were different; this is ascribed to metal chelates of DPA. As DPA moves up the paper, it chelates with metal impurities in the chromatographic paper. The chelates have lower R_f values than free DPA which is the fastest moving spot. This condition arises only when the amount of DPA exceeds the chelation capacity of metal impurities in the system. Chromatographic paper pre-washed with Na ethylenediamine tetraacetate to remove the metal impurities gave only a single spot. Chromatography in a formic acid-containing solvent did not produce the chelate spots. A possible explanation is advanced for this behavior. A sensitive, simple spectrophotometric assay of DPA is described based on optical density at the wave length of maximal absorption of DPA, 273 m.Professor Dr. A. Rippel zum 70. Geburtstag.International Cooperation Administration Fellow, 1955–57.