To preserve ammonia stability for measurement, which handling step is recommended?

• A. Draw into a pre-chilled tube and place on ice
• B. Keep at room temperature
• C. Delay analysis until later
• D. Expose to light

Answer: (A)

Ammonia in a collected specimen is unstable and can change rapidly after collection due to ongoing cellular metabolism and bacterial activity. Cooling the sample quickly slows these processes, preserving the ammonia concentration as close as possible to the level at draw. Drawing into a pre-chilled tube minimizes any initial warming, and placing the sample on ice keeps it cold until analysis, which is essential for accurate measurement.

Keeping the sample at room temperature allows enzymes and bacteria to produce more ammonia, skewing results. Delaying analysis provides more time for changes to occur. Exposing the sample to light does not improve ammonia stability and is not helpful for this measurement.