Spectrochemical Analysis by X-Ray Fluorescence pp 159-170 | Cite as

# Determination of High Concentrations with Calibration Curves

Chapter

## Abstract

The fluorescent intensity of a component is, in a first approximation, proportional to the concentration. The precise composition is determined with the aid of standard samples. For mixtures consisting of two and three components, the graphical method of determining the concentration is commonly used. Calibration curves are obtained by measuring samples of known composition for each component and by presenting graphically the relationship between intensity and concentration. The effect of associated components on the fluorescent intensity is evident from the fact that curves instead of straight lines are obtained, where the calibration curves for one and the same component may have different curvatures depending upon the associated components. The calibration curve used for determining niobium oxide in a mixture with tantalum oxide, for example, has a different curvature than the calibration curve used for determining niobium oxide in a mixture with titanium oxide (Figure 15.1). In order to balance as much as possible the differences incurvature between individual calibration points, the regression coefficient may be calculated first and the corresponding regression curve may then be plotted. The calibration curve for a two-component mixture is given approximately by the following function (see Chapter 12):where

$$\frac{{{N_A}}} {{{N_{A100}}}} = \frac{{{C_A}}} {{{C_A} + {C_B}{r_{AB}}}}$$

*r*_{ AB }is the regression coefficient. The complete curve is determined by one standard sample.## Keywords

Fluorescent Intensity Calibration Curve Correction Factor Niobium Oxide Tantalum Oxide
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Plenum Press, New York 1972