What is the recommended preservative for a water sample collected for lead and copper analysis?

The recommended preservative for a water sample collected for lead and copper analysis is nitric acid. This preservative is crucial because it serves to acidify the sample, which helps to keep lead and copper in a stable form and prevents the precipitation of these metals. By lowering the pH of the sample, nitric acid also inhibits any biological activity that could interfere with the analysis, thereby ensuring the accuracy of the results.

In lead and copper testing, maintaining the integrity of the sample is paramount, and the use of nitric acid as a preservative is standard practice as it aligns with laboratory methodologies and guidelines set by regulatory bodies. Instability in samples can lead to erroneous results, highlighting the importance of proper preservation techniques in water quality testing.