The determination of cystine. Use of the Zeiss photometer

Abstract

The color developed in the Sullivan method (and its modifications) may be detd. as an extinction coefficient by the Zeiss photometer employing light of wave length 530 m[mu] (filter No. 53). The color developed from cystine by the original Sullivan technique is subject to a variation of [plus or minus]25%. O interferes in the color development. By using a modified Lugg technique whereby the O effect is eliminated, the variation is reduced to [plus or minus]8%. Cystine, in pure solution, may be detd. with an approximate error of [plus or minus]5% with an outside limit of [plus or minus]15% which is reduced in the presence of hydrolyzed casein to [plus or minus]8%. Cysteine in pure solution may be detd. with an error of [plus or minus]4%. A method of determining cystine in hydrolyzed proteins is indicated.