What can be added to samples collected for heavy metal analyses to preserve them?

To preserve samples collected for heavy metal analyses, the addition of nitric acid is common practice. Nitric acid acts as a preservative by adjusting the pH of the sample, preventing the precipitation of metal hydroxides, and inhibiting biological activity that could alter the sample’s composition over time. Additionally, nitric acid helps to dissolve certain metal complexes that may otherwise remain in solid form, ensuring that the heavy metals of interest remain in a detectable dissolved state for accurate analysis.

Other acids listed, such as acetic and sulfuric acids, can alter the chemical structure of the metals being tested or may not provide the same effectiveness in preserving the sample for the heavy metals of interest. Hydrochloric acid can also pose issues with specific metal ion interaction or solubility, making nitric acid the most suitable choice for preserving samples meant for heavy metal analysis by stabilizing the sample integrity and composition during storage and transport.