Britannica Sources used in this answer

Why is nitric acid added to water samples analyzed for trace metals?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Viking 1 on Mars — sample preparation Viking 1's sample scoop, poised to extract material from the surface of Mars.

In analytical chemistry, nitric acid is added to water samples intended for trace metal analysis primarily to ensure the stability and solubility of the metals.

By acidifying the sample, the nitric acid maintains the metals in a dissolved state, preventing them from precipitating out of the solution or adsorbing onto the walls of the sample container, which would otherwise lead to inaccurate measurements.12

As a strong acid and a powerful oxidizing agent, nitric acid is highly effective at dissolving many metals and keeping them in an aqueous, ionic form suitable for laboratory analysis. This process is a standard step in the preparation of inorganic samples to ensure that the concentration of the analytes remains representative of the original water source throughout the storage and handling period.312