For how long can samples be preserved using Nitric Acid?

The preservation of samples using Nitric Acid is particularly relevant in the context of water quality testing, especially for metals analysis. When samples are acidified with Nitric Acid, it helps in stabilizing the sample by preventing precipitation and adsorption processes that can alter the analyte concentrations over time.

This method ensures that metal ions remain in solution and their concentrations do not change before analysis. Generally, samples preserved with Nitric Acid can be kept for a duration of 6 months and still preserve their integrity and accuracy for testing. This timeframe allows laboratories enough time to process and analyze samples without the risk of significant degradation or alteration in the metal concentrations due to environmental factors.

The other time frames mentioned do not reflect the accepted standards for sample preservation with Nitric Acid, as shorter periods may not provide sufficient leeway for laboratory scheduling and longer periods may lead to inaccuracies in results as the sample may begin to deteriorate or change. Therefore, 6 months is the most appropriate and widely accepted duration for preserving samples treated with Nitric Acid.