DETERMINATION OF NITRATE NITRITE BY SFA

1 In a segmented-flow analysis (SFA) system, the sample is first subjected to dialysis. Nitrate ions from the extract pass the membrane and are taken in an understream of ammonium chloride. The nitrate is then reduced to nitrite by means of copper-coated cadmium. Next a-naphtylamine and sulphanilamide are added, so that in the add medium present a red-coloured diazo compound is formed. Its absorbance is measured at a wavelength of 540 nm. 

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

The dialysis serves to separate nitrate ions from interfering substances like colloids and coloured organic compounds. 

The coleur reagent is known as the Qriess-llosvay reagent. 

1 This procedure yields a standard curve that is linear up to approximately 65 mg/L 

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