ASTM D8001 – 16: Kieldahl nitrogen by IC – including total phosphorus Standard Test Method for Determination of Total Nitrogen, Total Kjeldahl Nitrogen by Calculation, and Total Phosphorus in Water, Wastewater by Ion Chromatography.
Traditional Kjeldahl nitrogen is determined by digesting the sample with sulfuric acid and titrating the released ammonium.
The new IC method uses alkaline persulfate for the digestion. Organic nitrogen will be converted to nitrate. In addition organic phosphorus coverts into phosphate. This allows to determine total nitrogen and total phosphorus in one run.
- Total nitrogen (TN)
- Total Kjeldahl nitrogen (TKN)
- Total phosphorous (TP)
ASTM D8001 describes the digestion as well as the IC analysis. The standard can be performed applying the Metrosep A Supp 16 – 250/4.0 column. Example chromatograms are shown in the standard.