Is it possible to measure nitrogen colorimetrically in solids such as sludge?

Document ID

Document ID TE4374

Published Date

Published Date 03/21/2019
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Question
Is it possible to measure nitrogen colorimetrically in solids such as sludge?
Summary
Measure nitrogen colorimetrically in solids such as sludge
Answer
It is going to be difficult to get a homogeneous sample and significant dilution will most likely be required, but it is possible to get a good estimate. Below are some helpful hints:
  • Perform a TKN test using the Digestahl and a spectrophotometer and only use the results for process control. The assumption is that most natural fertilizers or manure will not contain that much inorganic nitrogen. Typically fertilizer manufacturers will need to test for total nitrogen but manure can be tested with TKN.
  • Hach does not have a TKN reduction reagent for fertilizers with mostly inorganic nitrogen, but one could be created easily. The formulary for this reagent is 50% sucrose and 50% salycilic acid. In this case, more sulfuric acid needs to be added as well.

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