DETERMINATION OF NITRATE-NITROGEN BY ISE

1 After buffering the ionic strength of the water extracts by a phosphate solution, the nitrate ions are detected direotiy with an ion-selective electrode (ISE). 

2 This determination may be carried out on extract 3.1 (extraction with water). 

This method may be used for the determination of nitrate in piant materiai oniy when the nitrate oontent is high (0.5 mmoi/kg). At iower ieveis the interferences by inorganic but espeoiaiiy organic anions are too strong. The nitrate concentration at which the interferences are negiigibie depends on the piant species (Novozamsky et ai., 1983). 

The addition of phosphate and Ai-resin aiso serves the purpose of buffering the ionic strength. 

1 The detection limit is approximately 0.1 mmol/L in the extract. The determination limit is approximately 0.3 mmol/L (5 respectively 15 mmol/kg in the dried plant 

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