Problems associated with the automated analysis of mixtures of amino acids.

91 in an alkaline Polycell solution for at least 24 h before analysis. When these steps are taken blockage of the manifold occurs infrequently. E excretion in man is predominantly urinary; about 10% of the intake is excreted in the faeces. T h e main source of error in a N balance study is in the estimation of dietary N. Because of the mixed nature of the diet it is difficult to obtain a truly homogeneous sample and to draw from it representative portions. This difficulty can be overcome to a great extent by mincing all meat and vegetables, by using an efficient homogenizer, and sampling by siphon while mixing. Values for N balance have been obtained for many patients in the Metabolic Unit. Large numbers of samples are required and these must be analysed under comparable conditions. We have found that the Technicon AutoAnalyzer provides an accurate and reproducible alternative to the manual Kjeldahl technique.