A collaborative study on the determination of free amino acids in blood plasma

Abstract

Abstract Collaborative work to determine the amino acid, taurine, urea and ammonia contents of a standard mixture of amino acids and of blood plasma from a preruminant and a ruminant calf was carried out at four laboratories to assess the accuracy of the ion‐exchange column chromatographic technique. Samples of blood plasma were deproteinised by the organising laboratory and by the collaborating laboratories using their own methods. For the standard amino acid mixture the mean absolute deviation was 0.036 of the true concentration. This compared favourably with results from previous collaborative trials on protein hydrolysates. The mean absolute deviations were 0.192 for preruminant calf blood deproteinised by the organising laboratory and 0.159 for blood deproteinised by the collaborating laboratories. Comparable values for ruminant calf blood were 0.149 and 0.117, respectively. These results were much poorer than those obtained for protein hydrolysates and possible explanations are put forward for these different degrees of precision.