An automated microassay for blood ammonia.

A microassay for blood ammonia has been developed. After dilution, blood is dialyzed by a continuous flow procedure, and the ammonium ions in the dialysate are assayed colorimetrically by the hypochlorite-phenol Berthelot reaction. Concentrations from 1 to 400 mumol/l NH+4 can be measured in a 50 mul whole blood sample. Using slight modifications, concentrations up to 800 mumol/l NH+4 can be determined. The precision, accuracy, sensitivity, and specificity of the method have been studied. In man, the usual values (mean +/- 2 SD) found are 27.4 +/- 10.2 mumol/l NH+4 in arterial blood, 20.9 +/- 9.8 mumol/l in venous blood. The usual values in rats and mice are very close to those given for man.