Replacement of mercury by copper as a Kjeldahl catalyst for the determination of the total nitrogen in cheese

Abstract

The standard method for the determination of total nitrogen in cheese uses toxic mercury compounds as catalysts in the Kjeldahl digestion. These compounds have been successfully replaced by copper sulphate in a procedure adopted after the determination of optimum digestion parameters. The procedure was tested using a wide variety of cheeses and the results were compared with those found by the standard method employing a mercury(II) sulphate catalyst. Results were in good agreement for all cheeses.