Richard J. Henry

Determination of Ceruloplasmin Oxidase in Serum

Summary A method for determination of ceruloplasmin in serum is presented in which rate of oxidation of p-phenylenediamine is measured spectrophotometrically or photometrically. Correction for catalytic oxidation by free metals present is made by reading the test against a serum blank in which enzymatic activity is inhibited by azide. The effects of pH and temperature on the reaction have been investigated and normal values obtained by our method. Ethylenediaminetetraacetate significantly inhibits enzymatic oxidase activity of serum.

Determination of α-amino acid nitrogen in urine.

Summary A modification of the photometric copper phosphate method for determination of α-amino acid nitrogen in urine has been presented. A comparison of results obtained in urines by the copper phosphate, naphthoquinone and gasometric-ninhydrin methods indicates that the specificity of the copper phosphate and naphthoquinone methods is materially improved by preliminary isolation of the amino acids on an ion exchange column.

A highly specific new method for the determination of cystine and cysteine and its application to urine.

Abstract A new and highly specific color reaction for determination of cystine is presented. Cystine is reduced to cysteine, which is then reacted with 2,6-dichloro- p -benzoquinone under specified conditions to produce an intense color with an absorption maximum at 510 mμ. The color follows Beers Law and is unaffected by other sulfhydryl compounds and reducing agents. The reaction is about five times more sensitive than the reduction of Folin reagent. This reaction was applied to cystine isolated from urine as the cuprous mercaptide. Quantitative recovery from urine was consistently obtained and the precision of the method was ±4.8% (95% limits). The cystine excretion for normal subjects was 8.2 to 88.1 mg/24 hr. A statistical comparison of several conventional techniques with the new one revealed no significant contribution of other sulfhydryl compounds to the results obtained by the methods of Medes and Padis or Shinohara but the method of Sullivan was found to be inaccurate.

Determination of calcium in biologic material by the chloranilate method.

Summary The Ferro-Ham chloranilate procedure for determination of serum calcium has been investigated. Modifications of this procedure are presented for determination of urine and fecal calcium and ultramicro modification for determination of serum calcium is described. Presence of turbidity, apparently lipid in nature, in final solution constitutes a source of significant positive error in the chloranilate method for determination of calcium in serum. This turbidity can be removed by ether extraction. Results obtained by the chloranilate method have been compared with the Clark-Collip procedure.