Patent ID: 6040190
Filing Date: 2000-03-21
Classification: G01N,Y10T

Abstract:
A method of spectroscopically determining the concentration c of a sample of a nonlinear absorbent that does not conform to Lambert-Beer's law and so exhibits a non-linear relationship between concentration and absorption, the method comprising:(a) forming a mathematical model of said nonlinear absorbent, said model including a plurality n, n.gtoreq.2, of model components each of which conforms to Lambert-Beer's law, the step of forming the mathematical model comprising:(i) taking calibration spectroscopic data of absorption a(.lambda.) at the plurality n of wavelengths .lambda. for each of a plurality of calibration samples of said non-linear absorbent, said calibration samples having known concentrations; and(ii) from the calibration spectroscopic data taken in step (a)(i), determining parameters of the plurality of model components that would allow the plurality of model components to model the non-linear absorbency behavior of said absorbent by satisfying the following equation:a(.lambda.)=(.epsilon..sub.1 (.lambda.).multidot.c.sub.1 +.epsilon..sub.2 (.lambda.).multidot.c.sub.2 + .multidot. .multidot. .multidot. .epsilon..sub.n (.lambda.).multidot.c.sub.n).multidot.dwhere each model component .epsilon..sub.i (.lambda.).multidot.c.sub.i, 1.ltoreq.i.ltoreq.n, has a spectral absorption value given by .epsilon..sub.i (.lambda.) and a concentration c.sub.i ; and(b) applying the mathematical model to the sample of the absorbent, the step of applying the mathematical model comprising:(i) taking measurement spectroscopic data for a sample of said absorbent of unknown concentration at the plurality n of wavelengths;(ii) applying the equation set forth in (a)(ii) to said measurement spectroscopic data to determine the concentration values c.sub.i of the plurality of model components corresponding to the measurement spectroscopic data; and(iii) from the concentration values c.sub.i of the plurality of model components, calculating C.