Total Kjeldahl nitrogen (TKN) measurement context
EPA Method 351.2. Sulfuric acid digestion converts organic nitrogen and ammonia to ammonium, which is then measured by colorimetry. TKN is organic nitrogen plus ammonia; some industrial nitrogen compounds are not converted by the digestion. Reported as mg/L nitrogen.
Connect the parameter to the sample plan
Specify grab or composite collection where applicable, the reporting unit and any field or preparation requirements. Keep nitrogen, phosphorus, solids and demand measurements on their correct reporting basis.
Include the complete project requirement
Provide the matrix, target analytes, required method, fraction, units and reporting limits. Include the permit or monitoring instructions where results will support a regulatory submission. Naming this method does not establish blanket compliance eligibility.
Resolve collection before sampling
Use the bottle, preservation and delivery instructions assigned to the agreed scope. Identify each location and collection time, and document any deviation. The final analytical plan must fit the submitted material and its intended use.
Related testing & guidance
Technical & service references
Vanguard service detailsSource review: November 8, 2026. The agreed method and project scope govern the testing.