Metrohm 909 UV Digester - Manual (Page 38)

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909 UV Digester
Note
Nitrite interference
Nitrite forms from the effects of UV radiation on nitrate. It is voltam-
metrically active and shows a wide peak at –1.2 V. This peak can over-
lap with signals from metals such as zinc, thereby causing interference.
You can prevent this reaction in two ways:
￭ Add acid to the sample solutions using HCl instead of HNO
3
.
￭ Reduce the nitrite using sulfamic acid: add 0.025 mL ( β(sulfamic
acid) = 40 g/L) to 10 mL of open, hot sample solution.