When analyzing samples for haloacetic acids 5 (HAA5), what is added to the sample container to quench more HAA5 formation?

When analyzing samples for haloacetic acids 5 (HAA5), what is added to the sample container to quench more HAA5 formation?

• A. HNO3
• B. NH4Cl
• C. NO2
• D. dilute H2SO4

Answer: (B)

Quenching residual chlorine right after collection is essential to prevent more HAA5 from forming in the sample during storage and transport. Ammonium chloride is used because the ammonium reacts with the remaining chlorine to form chloramines, quickly eliminating free chlorine and stopping additional reactions with natural organic matter that would produce haloacetic acids. This keeps the measured HAA5 reflecting the level at the moment of sampling. Strong acids would just change the pH and wouldn’t neutralize chlorine, and nitrite isn’t the standard quencher for this purpose, so they don’t prevent ongoing HAA5 formation in the same reliable way.

Quenching residual chlorine right after collection is essential to prevent more HAA5 from forming in the sample during storage and transport. Ammonium chloride is used because the ammonium reacts with the remaining chlorine to form chloramines, quickly eliminating free chlorine and stopping additional reactions with natural organic matter that would produce haloacetic acids. This keeps the measured HAA5 reflecting the level at the moment of sampling. Strong acids would just change the pH and wouldn’t neutralize chlorine, and nitrite isn’t the standard quencher for this purpose, so they don’t prevent ongoing HAA5 formation in the same reliable way.