Purification of gaseous CO from Fe(CO)5 traces formed in steel storage cylinders

High purity gaseous CO stored in a steel tank contains a volatile iron carbonyl compound that easily contaminates electrochemical samples saturated with CO. The impurity yields a voltammetric reduction peak at −2.0 V in non-aqueous solvents (acetonitrile, acetone and tetrahydrofurane) and IR absorption at 2024 and 2001 cm−1 characteristic of metal carbonyls. This impurity is Fe(CO)5 and can be removed efficiently by bubbling CO through aqueous NaOH solution. This purification procedure is adequate for the electrochemical studies of metal carbonyls under CO atmosphere. Failure to remove this volatile impurity may lead to misinterpretation of electrocatalytic and ligand substitution reactions.