ATMOSPHERIC-PRESSURE MICROWAVE SAMPLE PREPARATION PROCEDURE FOR THE COMBINED ANALYSIS OF TOTAL PHOSPHORUS AND KJELDAHL NITROGEN

An atmospheric pressure microwave digestion method has been developed for the combined analysis of total phosphorus and Kjeldahl nitrogen in complex matrices, In comparison to the digestion steps in EPA Methods 365.4 (total phosphorus) and 351.x (Kjeldahl nitrogen), this method r equires less time, eliminates the need for a catalyst, and reduces the toxicity of the waste significantly. It employs a microwave-assisted digestion step, using refluxing borosilicate glass vessels at atmosphe ric pressure, Traditionally, this method has a time-consuming sample p reparation step and generates toxic waste through the use of heavy met al catalysts, These advantages are gained by the combination of a high boiling point acid (sulfuric acid) and the application of focused mic rowave irradiation, which enhances the digestion process by direct ene rgy coupling, NIST standard reference materials 1572 (citrus leaves), 1577a (bovine liver), and 1566 (oyster tissue) and tryptophan were ana lyzed to validate the method. Phosphorus concentrations were determine d by the colorimetric ascorbic acid method outlined in EPA Method 365. 3, Kjeldahl nitrogen concentrations were determined using EPA Method 3 51.1. The results of the analyses showed good precision and are in exc ellent agreement with the NIST published values for both elements.