Abstract
We have found that a fair degree of accuracy can be obtained in testing for pregnancy by oxidizing 1 cc. of urine with 1 drop of 0.5% hydrogen peroxide, after which 5 drops of a 1% aqueous solution of phenylhydrazine hydrochloride are added and 5 drops of a 5% aqueous solution of methyl cyanide, followed by 5 drops of concentrated hydrochloric acid. It is then put into a boiling water bath and allowed to react for 25 minutes. After this time the reaction is said to be positive if a russet color develops and a flocculent precipitate appears. A negative reaction is shown by the absence of a precipitate or the presence of a powdery one and usually a straw color. All reagents should be fresh at the time the tests are made.
It was found that a modification of this test, which appears to be more sensitive for certain of the hormones, could be adapted to titration methods. This modification is carried out as follows:
To 1 cc. of urine, one drop of 0.5% hydrogen peroxide is added and this allowed to stand for 3 minutes. Five drops of a 1% solution of phenylhydrazine hydrochloride are added, followed by 5 drops of a 5% aqueous solution of potassium ferricyanide. This is allowed to stand for 10 minutes at room temperature and then put in a boiling water bath for 15 minutes. Upon removal from the water bath, one drop of concentrated hydrochloric acid is added and this is followed by an excess of sodium hydroxide. Dilute hydrochloric acid is then added by titration until a definite end point is obtained. (The color changes from an orange to a green to a prussian blue.) It was found that it required much less dilute hydrochloric acid to obtain the end point in pregnancy specimens than was required in the case of non-pregnancy female urine specimens, and that various pregnancy tests fall in a given range, while normal tests fall in another more restricted range.
Get full access to this article
View all access options for this article.