Ektachem multilayer dry-film assay for ammonia evaluated

We evaluated the Kodak Ektachem multilayer dry-film method for ammonia. Within-day precision (CV) was 5.9% and 2.7% at ammonia concentrations of 53 and 654 mumol/L, respectively. Between-run precision (CV) was 7.8% and 7.3% at 51 and 109 mumol/L, respectively. Correlation with a manual ion-exchange chromatography-Berthelot reaction-based method (x) was good (y = 0.96x - 1.37; r = 0.984; SEE = 9.16). The response of the method varies linearly with ammonia concentration up to 900 mumol/L. Bilirubin less than or equal to 270 mg/L, triglycerides less than or equal to 6.0 g/L, and slight hemolysis did not interfere. The concentration of ammonia in plasma of 120 healthy adults was 16-53 mumol/L (nonparametric central 95 percentiles).