What is the hold time for a nitrate sample preserved with sulfuric acid?

The hold time for a nitrate sample preserved with sulfuric acid is indeed 28 days. This period is crucial as it ensures the integrity and accuracy of the sample for analysis. During this time, the acidic environment helps to stabilize the nitrate concentration and prevents microbial activity that could alter the sample's composition. Adhering to this hold time is essential in wastewater treatment and analysis to ensure reliable results that reflect the actual conditions of the sample at the time it was collected. The preservation technique with sulfuric acid is widely accepted and validated in standard methods for water and wastewater analysis, reinforcing the significance of the 28-day hold time.