Determination of 15N-ammonia by chemical ionization mass spectrometry.

The tracing of ammonium nitrogen is important in hepatic diseases, especially in liver cirrhosis with hyperammonemia. In this paper, a new convenient method is described for determining stable isotope 15N-labeled ammonia using the Conway apparatus and chemical ionization mass spectrometry. The minimum quantity of ammonia necessary for reliable measure of 15N content was 0.1 muMol. The average error was 5.3%. In clinical application, 4 ml of blood after oral administration of 1 g of 15NH4Cl was sufficient for measurement.