A new rapid method for quantification of nitrogen in human serum employing the 14N(p,p' gamma)14N reaction: application to human pregnancy.

The total nitrogen concentrations in dried serum from 54 pregnant women and 17 newborn babies were determined by a new application of the 14N(p,p' gamma)14N reaction resonance at 3.9 MeV. The samples were bombarded in a He atmosphere by 4.1 MeV protons from a tandem Van de Graaff accelerator. The mean dry-weight nitrogen concentration in serum sampled during early pregnancy (6-12 weeks; 13.9 g per 100 g +/- 5.4%) was significantly higher than that in serum sampled during late pregnancy (38-42 weeks: 13.0 g per 100 g +/- 3.9%, p less than 0.001) and than that in serum taken from the umbilical cord (13.3 g per 100 g +/- 4.6%, p less than 0.01). The nitrogen levels measured using this rapid nuclear technique, applied for the first time to human serum analysis, agree well with parallel Kjeldahl analyses.