A SIMPLE METHOD FOR ANALYZING COMPLICATED ABSORPTION CURVES, OF USE IN THE COLORIMETRIC DETERMINATION OF URINARY STEROIDS

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Abstract
A simple equation has been developed which makes for easy analysis of mixed absorption curves provided the absorption curves of the contaminating substances closely approximate straight lines in the region of the absorption maximum produced by the compound being measured. The background colors produced by the various modifications of the Kober test now in use for the measurement of urinary steroids closely approach straight lines so that the method is very useful in routine measurements of urinary estrogen and dehydroisoandrosterone. The equation is as follows: [image]calculated density due to compound X having an absorption max. at wave length x. The evaluation of this density in terms of the pure compound is obtained by study of the densities of various quantities of the pure compound at the 3 lengths a, b, and x. A more general solution is given also where wave lengths a and b are not equidistant from wave length x. No constants pertaining to the actual curves in question are necessary in either equation. Actually all of the background color occurring between wave lengths a and b, together with a portion of the color due to compound X, is subtracted from the observed density. However, the fraction of the total absorption due to X which is subtracted bears a constant relation to the total''absorption, hence, none of the usual constants enter into the equations.