A new approach for obtaining total tryptophan recovery in plasma samples deproteinized with sulphosalicylic acid

The treatment of plasma with a sodium dodecy sulphate solution before deproteinization with sulphosalicylic acid is described. With this treatment, the liberation of tryptophan from plasma albumin is complete and its determination can be made directly, together with that of other amino acids and related compounds, by automatic ion-exchange chromatography, eliminating the need for an extra analysis for the accurate determination of this amino acid. Results of tryptophan recovery tests, carried out both on plasma samples simply deproteinized with sulphosalicylic acid and on other samples pre-treated with sodium dodecylsulphate solution are reported. These results are also compared with those obtained when trichloroacetic acid was used as deproteinizing agent. A recovery study on a human albumin (fraction V) solution containing a known amount of tryptophan is also described.