Food Safety and Environmental Stewardship Program

A non-polluting alternative catalyst was used in a U.S. Environmental Protection Agency (EPA) Kjeldahl digestion procedure for water and wastewater samples. The colorimetric semiautomated block digestion method (EPA Method 351.2) was essentially unchanged except that 1 mL of a saturated solution of titanium dioxide was added to the digestant mixture, instead of 2g mercuric oxide. Titanium dioxide is a nontoxic compound, which makes an excellent replacement in total Kjeldahl nitrogen (TKN) determination. Samples were digested and then placed on a flow injection autoanalyzer for ammonia determination. All other digestion and analysis procedures were the same as in the original method. Detection limit for TKN was 0.1 mg/L. Recovery of glutamic acid averaged 96.2%. Recoveries of standard reference water samples over a 9 month period averaged >95%.