Abstract: The present disclosure deals with the biochemistry of reagents useful in the detection of ammonia in liquid samples. Specifically, the present disclosure is directed to a technical improvement of an enzyme-based test for ammonia that can be used for analysis of plasma samples taken from patients in clinical settings, among other uses. In this regard, stability of a reagent containing NAD(P)H is improved, enhancing shelf life and results in the detection of ammonia. In an exemplary reagent ammonia released as a result of NAD(P)H decay is scavenged using an enzymatic reaction to convert the ammonia using GLDH, NAD(P)H and 2-oxoglutarate, thereby forming L-glutamate, NAD(P)+ and H2O in the NAD(P)H containing reagent.