Nagahiro, T.; Uesugi, K.; Satake, M. Column Preconcentration of Cobalt Using 4-(5-Bromo-2-Pyridylazo)-1,3-Diaminobenzene and Ammonium Tetraphenyl-Broate Supported on Naphthalene and Its Analysis Using Atomic Absorption Spectrometry . ajc 2010, 5, 743-748.