Which compound is utilized for preserving an Ammonia sample?

Preserving an ammonia sample is crucial for accurate analysis, as ammonia can volatilize and be lost from the sample over time. Sulfuric acid is often used for this purpose because it reacts with ammonia to form ammonium sulfate. This process helps to stabilize the sample by converting ammonia gas into a more stable compound, thus preventing its loss from the solution.

The use of sulfuric acid also lowers the pH of the solution, which further inhibits the escape of ammonia into the atmosphere, ensuring that the concentration of ammonia in the sample remains representative of the sample taken from the source. This preservation technique is important in various analytical methods used to determine ammonia concentrations, such as colorimetric assays or ion chromatography.

In contrast, the other compounds listed do not serve the same role in preserving ammonia samples. Sodium chloride may help with ionic strength but does not prevent ammonia loss effectively. Sodium bicarbonate acts more as a buffering agent and does not stabilize ammonia in samples. Acetic acid, while it can influence pH, is not effective for preserving ammonia in the same way as sulfuric acid.