Ammonia
A fast enzymatic analysis for plasma ammonia
PRINCIPLE
i) Ammonia is converted to L-glutamate by glutamate dehydrogenase (GLDH) in the presence of α-ketoglutarate 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.
TECHNICAL SUMMARY
| Samples | > | Plasma |
| Sample volume | > | 200 µl (2 x 100 µl) |
| Analysis time | > | 20 seconds (from injection) |
| Linearity | > | 0 - 800 µmol/L (0 - 13.5 µg/ml) |
| Precision | > | C.V. of 2% @ 500 µmol/L (ca. 8.5 µg/ml) |
| Accuracy | > | Method comparison vs Spectrophotometric UV (Sigma): y (Analox) = 0.97x + 0.28 µg/ml, r = 0.968, n = 33 |
| Detection limit | > | 18 µmol/L (ca. 0.3 µg/ml) |
| Reagent Stability | > | Shelf-life unopened: 9 months stored at 0-5°C. Shelf-life reconstituted: NADH/α-ketoglutarate, 7 - 10 days stored at 0-5°C; POD reagent 5-6 weeks at 0-5°C. |
Notes:
A sample blank allows for interference by endogenous NADH consuming reactions.