Evaluation of the Rupp-Schied-Thiel Method as a Test for Thiocyanate in the Urine. ∗

Abstract

While applying the Rupp-Schied-Thiel^{1, 2} thiocyanate procedure to pathological urines, cancerous, and non-cancerous and to normals, as given in the preceding paper, the question arose as to the degree of specificity of the reaction when applied to a number of substances knbwn to occur in urine or possibly there. Among the substances possibly in urine found to behave like thiocyanate in the Rupp-Schied-Thiel procedure are ergothioneine, urinary protease, and oxyproteic acids, and to some degree uric acid. Four normal urines were studied for total apparent thiocyanate by the Rupp-Schied-Thiel procedure; for ergothioneine-like material color-imetrically against blood ergothioneine by the Behre and Benedict 3 procedure; urinary proteose by the method of Oriel and Barber 4 ; and for oxyproteic acids as barium salts according to Pregl. 5 In each case the thiocyanate equivalent of the fractions, (1) ergothioneine-like material, (2) proteose, and (3) barium oxyproteic acids was determined in the Rupp-Schied-Thiel procedure. The thiocyanate equivalents of fractions listed subtracted from the total apparent thiocyanate shows much less thiocyanate than given by the Rupp-Schied-Thiel method. The conclusion is drawn that the Rupp-Schied-Thiel method is not a measure of thiocyanate if applied directly to the urine. The same objection holds for the Munk 6 gravimetric method which depends on the precipitation of thiocyanate by silver nitrate and melting the precipitate with sodium carbonate and potassium nitrate to oxidize the sulfur to sulfate, which is then precipitated as barium sulfate. Other urinary sulfur compounds than thiocyanate are included in this method.

The interfering material, however, can be eliminated. Thus, based on the findings that strong alcohol does not dissolve certain interfering substances such as ergothioneine, proteose, the barium salt of oxyproteic acid, or barium urate but does dissolve barium thiocyanate a somewhat improved procedure has been employed as follows: An aliquot of urine generally 50 cc. is treated with a saturated aqueous solution of barium hydroxide as long as a precipitate forms.