DETERMINATION OF TOTAL NITROGEN IN SEDIMENTS BY USING HIGH-PRESSURE BOMBS AND ION CHROMATOGRAPHY

The standard method for the determination of organic nitrogen in water samples has in the past been based on Kjeldahl's digestion technique which determines nitrogen in the triply negative state. In the presenc e of sulfuric acid, potassium sulfate, mercuric sulfate and a catalyst , amino nitrogen is converted to ammonium sulfate. Free ammonia and am moniacal nitrogen are also converted to ammonium sulfate which can be determined spectrophotometrically, or by titration with a standard min eral acid. However, this method is time consuming and the accuracy is variable. An alternative method for the determination of organic nitro gen is the alkaline persulfate digestion technique which oxidizes all the nitrogen in the sample to nitrate as the sole product using potass ium persulfate in a strongly alkaline environment under high pressure and temperature. In this paper, a methodology for total nitrogen deter mination in sediments is developed using 23 ml high-pressure bombs wit h potassium persulfate and sodium hydroxide. The determination of nitr ogen as nitrate was made by using ion chromatography. Urea was used as the nitrogenous compound to calibrate the methodology, which was chec ked using the Kjeldahl method and showed good agreement.