Photometric determination of cobalt by means of photochemically generated anti-2-furaldehyde 2-pyridylhydrazone

The photochemical syn-anti isomerization of 2-furaldehyde 2-pyridylhydrazone (FAPH) in ethanolic solutions has been investigated. A study of the infrared, visible and ultraviolet, and n.m.r. spectra of the two isomers was made. The syn-anti ratio at the photostationary state was determined. syn-FAPH scarcely reacts with metal ions but the anti-FAPH formed by irradiation gives sensitive reactions with several metal ions to form stable chelates. A photometric method for the determination of cobalt (0.025-1.0 microg/ml ) in aqueous ethanolic medium (50% v/v ) at pH 9.7 is described. A detection limit of 0.007 microg/ml and relative standard deviation of 0.5% were found. By consideration of the syn-anti ratio at the photostationary state, the stoichiometry of the chelate was determined. An application of this technique to determination of cobalt in environmental fume samples is also described.