Technical Summary: Blood Ammonia Analysis (Bulletin ref. TB058913G)
 

A fast enzymatic analysis for plasma ammonia.
 

Name:
Code:
Size:

Instruments:
 

Blood Ammonia
GMRD-162
2 x 10 tests; 140 analyser cycles. The number of tests may be doubled by using half-volumes (micro-method)
All GM7 Series analysers
 

Principle:

i) Ammonia is converted to L-glutamate by a-ketoglutarate in the presence of glutamate dehydrogenase (GLDH) and excess NADH in a brief pre-reaction:
 

ii) Under the conditions of the assay, the rate of oxidation of excess NADH by peroxidase (POD) is inversely proportional to ammonia concentration:
 

A sample blank allows for interference by endogenous NADH consuming reactions, etc.
 

Samples:
Sample volume:
Linearity:
Precision:

Accuracy:
 

Plasma
200 µl (2 x 100 µl)
800 µmol/L (13.5 µg/ml)
Typical within-run S.D. = 0.2 µmol/L; C.V. = 2 % @ 500 µmol/L

Method comparison vs Spectrophotometric UV (Sigma):
y (Analox) = 0.97x + 0.28 µg/ml, r = 0.968, n = 33
 

Reagent Stability:

Shelf life 12 months unopened when stored at 0 - 5°C. Reconstituted
NADH/a- ketoglutarate, 7 - 10 days (2 vials) if stored at 0 - 5°C.

Reference:

Plasma ammonia measurements using the Analox GM7 analyser, M.E. Haseler and S. Krywawych, Proceedings of the ACB National Meeting, Birmingham, UK, 1991.