[Usefulness of spectrophotometric methods Messineo and Musarra for free tryptophan determination in blood plasma].

The evaluation of usefulness of the Messineo and Musarra spectrophotometric method for free tryptophan determination in human blood plasma was studied. The method is based on the formation of pink-violet complex, between the indole compound and clearly-green chromophore, being a condensation product of cysteine with the furfural derivative of fructose. The precision and accuracy was estimated as well as the effect of serotonin and trichloracetic acid, used to protein precipitation, on the yield of coloured complex formation, was studied. The obtained results indicate on the great usefulness of this method for the free blood plasma tryptophan determination. However the condition of the exact results receiving is the complete removal of proteins and concentration of other indole compounds probably present in the sample, should be no greater than 0.3 microgram/cm3. The trichloroacetic acid showed no effect on the yield of coloured compound formation. The precision of this method expresses as the variation coefficient was equal 2.1% and recovery of tryptophan 97.3%.