Which parameter has no preservation required and a 28-day regulatory storage time?

Which parameter has no preservation required and a 28-day regulatory storage time?

• A. Chloride
• B. Total Chlorine Residual
• C. Ammonia
• D. Nitrate

Answer: (A)

In this context, hold time and preservation determine how long a sample can be stored before analysis and whether any treatment is needed to keep it stable. Chloride is chemically stable in water and does not change appreciably during storage, so no preservative is required. It can meet a 28-day regulatory hold time because the concentration remains reliable without special treatment. The other parameters can change during storage: total chlorine residual can decay or react, ammonia can volatilize or transform, and nitrate can be affected by microbial activity or chemical changes if not preserved. These require some form of preservation or have different hold-time constraints, so they don’t fit the combination of “no preservation required” and “28-day storage time.”

In this context, hold time and preservation determine how long a sample can be stored before analysis and whether any treatment is needed to keep it stable. Chloride is chemically stable in water and does not change appreciably during storage, so no preservative is required. It can meet a 28-day regulatory hold time because the concentration remains reliable without special treatment.

The other parameters can change during storage: total chlorine residual can decay or react, ammonia can volatilize or transform, and nitrate can be affected by microbial activity or chemical changes if not preserved. These require some form of preservation or have different hold-time constraints, so they don’t fit the combination of “no preservation required” and “28-day storage time.”