Substitution of Cupric Sulfate for Mercuric Oxide as Catalyst for the Kjel-Foss Instrument

Abstract

Abstract A mixture of cupric sulfate and titanium dioxide and cupric sulfate alone were evaluated as possible catalysts to replace mercuric oxide in the determination of protein nitrogen, using the Kjel-Foss automated instrument. It was necessary to modify the instrument to increase the digestion time from 6 to about 12 min to achieve acceptable protein nitrogen recovery with cupric sulfate as the catalyst. An experimental sample set of nitrogen-containing salts and American Association of Feed Control Officials check feed samples were analyzed with the Kjel-Foss instrument in its standard configuration with mercuric oxide and as modified with cupric sulfate as the catalyst. The average per cent nitrogen, standard deviation, and relative standard deviation with mercuric oxide and cupric sulfate were 10.37 and 10.36, 0.040 and 0.042, and 0.53 and 0.56, respectively. The substitution of cupric sulfate for mercuric oxide is feasible, and it eliminates the use of the potential pollutant, mercury.