Method for quantitative analysis of analyte in liquid sample using analytical element

Claim 1

In a method for quantitatively analyzing an analyte in a liquid sample by applying the liquid sample on one of a set of analytical elements and measuring a color developed in the analytical element through reflection photometry in which said set of analytical elements are the same elements as a standard element except for deviation of sensitivity to the analyte, but said deviation of sensitivity is essentially equivalent to each other among the set of analytical elements, a calibration curve of the standard element with respect to said analyte being predetermined, the improvement comprising the steps of: (I) applying two standard solutions containing the analyte in contents C 1 and C 2 different from each other on two analytical elements, respectively, these analytical elements being selected from said set of analytical elements, and measuring colors developed on the elements through reflection photometry to obtain optical reflection density values OD x1 and OD x2 , respectively; (II) preparing a linear equation for defining a relationship between an optical reflection density value OD x to be measured on an analytical element belonging to said set of the analytical elements and an optical reflection density value OD s being predetermined on the standard analytical element, in which the optical reflection density values OD x and OD s are those to be determined on colors developed on the respective elements upon application of a liquid sample containing the analyte in the same content C x , the preparation being made utilizing the calibration curve and the optical reflection density values OD x1 and OD x2 obtained in step (I); (III) applying a liquid sample containing the analyte in an unknown amount on an analytical element belonging to said set of analytical elements, and measuring a color developed on said element through reflection photometry to obtain an optical reflection density values; and (IV) determining the content of the analyte in the applied liquid sample according to the above-prepared linear equation and the predetermined calibration curve; wherein said linear equation is OD.sub.x =A·OD.sub.s +B in which A and B are constant values obtained from the equations: OD.sub.x1 =A·OD.sub.s1 +B OD.sub.x2 =A·OD.sub.x2 +B in which OD s1 is an optical reflection density value to be determined on the standard analytical element upon application of a liquid sample containing the analyte in the content C x1 , and OD s2 is an optical reflection density value to be determined on the standard analytical element upon application of a liquid sample containing the analyte in the content C x2 .