A PROCEDURE FOR THE SIMULTANEOUS DETERMINATION OF TOTAL NITROGEN AND TOTAL PHOSPHORUS IN FRESH-WATER SAMPLES USING PERSULFATE MICROWAVE DIGESTION

In the absence of a suitable method for routine analysis of large numbers of natural river water samples for organic nitrogen and phosphorus fractions, a new simultaneous digestion technique was developed, based on a standard persulphate digestion procedure. This allows rapid analysis of river, lake and groundwater samples from a range of environments for total nitrogen and phosphorus. The method was evaluated using a range of organic nitrogen and phosphorus structures tested at low, mid and high range concentrations from 2 to 50 mg l-1 nitrogen and 0.2 to 10 mg l-1 phosphorus. Mean recoveries for nitrogen ranged from 94.5% (2 mg l-1) to 92.7% (50 mg l-1) and for phosphorus were 98.2% (0.2 mg l-1) to 100.2% (10 mg l-1). The method is precise in its ability to reproduce results from replicate digestions, and robust in its ability to handle a variety of natural water samples in the pH range 5-8.