Which instrument is used for the enzymatic ammonia determination?

• A. UV Spectrophotometry
• B. Fluorometry
• C. Mass Spectrometry
• D. HPLC

Answer: (A)

Enzymatic ammonia determination often relies on a dehydrogenase reaction that uses NAD+/NADH. In a typical setup, the enzyme catalyzes a reaction where ammonia is incorporated or released, causing a change in the amount of NADH. NADH has a strong absorbance at 340 nm, so a UV spectrophotometer is used to monitor the increase or decrease in NADH concentration. The measured change in absorbance is directly related to the ammonia level, making UV spectrophotometry the standard instrument for this enzymatic method.

Fluorometry would require a fluorescent product to be formed, which isn’t the usual detection path for this assay. Mass spectrometry and HPLC are capable of measuring ammonia but represent different, more specialized approaches rather than the common enzymatic colorimetric/UV-detection method.