[Automated determination of total nitrogen in urine and feces]

Urine and stool total nitrogen was measured using the Carlo Erba Strumentazione NA 1500 nitrogen analyzer. Determinations were carried out on 10 mcl, 20 mcl and 50 mcl urine samples and on 20-50 mg stool samples. Both urine and stool data distributions were normal, thus indicating the reliability of the method. The NA and the classic Kjeldahl method gave very close results in the same urine specimen; slight and not significant differences were found in stool analysis, most likely caused by the poor homogeneity of the material. Due to the automation, they very short analysis time, the accuracy and the reproducibility of the results, NA 1500 can be used in clinical practice for nitrogen balance studies by direct measurement of losses.