In TNT880 for s-TKN™, how is the test result corrected to account for the dilution caused by volume additions of acid and base in the pretreatment?

Document ID

Document ID TE6379

Published Date

Published Date 10/22/2019
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Question
In TNT880 for s-TKN™, how is the test result corrected to account for the dilution caused by volume additions of acid and base in the pretreatment?
Summary
Correcting final result for volumes added in TNT880
Answer
When using Simplified TKN (s-TKN™) TNTplus Vial Test (0-16 mg/L N) (Product # TNT880), the final result should be corrected to account for the dilution caused by adding acid to drop the pH to less than 2 and base to neutralize prior to analysis. To do this, take the total volume of the sample prior to analysis (volume of acid added + volume of base added + original volume) and divided by the original volume. Multiply the final results for Total Nitrogen and NO 3 + NO 2 by this factor.

For example, if you had 1000 mL of sample originally and added 2 mL of sulfuric acid to drop the pH to less than 2, then added 4 mL of sodium hydroxide to neutralize the sample prior to analysis, the total volume of the pH adjusted sample is 1006 mL. The original volume was 1000 mL. 1006/1000 is 1.006. This means that you need to multiply your final results for Total Nitrogen and NO 3 + NO 2 by 1.006 to account for the volume change.

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