Chloride interference in total nitrogen analysis by the Kjeldahl method |
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Abstract: | Abstract Very low recovery of NH4+‐N was observed in total N determination of (NH4)2SO4 in KC1 solutions by a semimicro Kjeldahl method using permanganate and reduced iron to recover NO3‐ and NO2‐, whereas complete recovery was obtained in analysis of NH4+‐N in water, and of NO3 ?‐N or NO2 ?‐N in either water or KC1 solutions. The loss of NH4 +‐N observed with KC1 was attributed to the formation of NCl3 upon reaction of NH4 + with Cl2 generated during oxidation of Cl? by MnO4 ?. This difficulty is avoided by using K2SO4 instead of KC1 for extraction of inorganic N from soil. Complete recovery was obtained by adding 15N‐labeled NH4+, NO3‐, or NO2‐ to 0.5 M K2SO4 soil extracts, and total 15N analyses of the labeled extracts were in good agreement with values calculated from the additions of 15N and the total N contents of the soil extracts. |
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