What is the preservation method for Phosphorus, Total samples?

What is the preservation method for Phosphorus, Total samples?

• A. Analyze Immediately; 0.25h
• B. Add H2SO4 (sulfuric) to pH<2; Cool <=6C; 28D
• C. Filter Immediately; 48H
• D. Cool <=6 C; 7D

Answer: (B)

Preservation of total phosphorus samples relies on chemical stabilization and cold storage with a defined hold time to keep the phosphorus content stable until analysis. Specifically, you add sulfuric acid to bring the sample pH below 2, then cool it to 0–6 °C and hold for 28 days. Acidifying to pH below 2 prevents biological activity and minimizes changes in phosphorus forms that could occur during storage, while cooling slows down chemical and microbial processes. The 28-day hold is the standard period that ensures the sample remains stable for accurate measurement later, often prior to the digestion and analysis steps. Without acidification, phosphorus can shift forms or be affected by biological activity; simply cooling without acidification doesn’t provide the same stabilization, and options like filtering would exclude particulates and yield only dissolved phosphorus, which isn’t the total phosphorus value. Analyzing immediately avoids preservation altogether and isn’t compatible with the required holding protocol.

Preservation of total phosphorus samples relies on chemical stabilization and cold storage with a defined hold time to keep the phosphorus content stable until analysis. Specifically, you add sulfuric acid to bring the sample pH below 2, then cool it to 0–6 °C and hold for 28 days. Acidifying to pH below 2 prevents biological activity and minimizes changes in phosphorus forms that could occur during storage, while cooling slows down chemical and microbial processes. The 28-day hold is the standard period that ensures the sample remains stable for accurate measurement later, often prior to the digestion and analysis steps. Without acidification, phosphorus can shift forms or be affected by biological activity; simply cooling without acidification doesn’t provide the same stabilization, and options like filtering would exclude particulates and yield only dissolved phosphorus, which isn’t the total phosphorus value. Analyzing immediately avoids preservation altogether and isn’t compatible with the required holding protocol.