Concentration measuring method and fluorescent X-ray spectrometer

1. A concentration measuring method for measuring a concentration of an object component in a sample from a fluorescent X-ray intensity by means of a fluorescent X-ray spectrometer, comprising steps of:

acquiring spectrums of secondary X-rays generated by irradiating a plurality of standard samples, concentrations of the object component of which are zero and compositions of which are different from each other, with primary X-rays;

setting a subtraction formula by calculating constants α and β according to a plurality of formulas obtained by setting I=0 and assigning S and B, which are obtained from the spectrums acquired for a plurality of standard samples, to a subtraction formula I=S−αΔB−β (wherein I: a fluorescent X-ray intensity obtained by subtracting the background, S: a fluorescent X-ray intensity of the object component obtained from a spectrum, α and β: constants, and B: a scattered X-ray intensity obtained from a spectrum) for subtracting the background from the fluorescent X-ray intensity of the object component, which is obtained from a spectrum;

irradiating the sample with primary X-rays;

acquiring a spectrum of secondary X-rays generated from the sample;

obtaining a fluorescent X-ray intensity of the object component included in the sample from the acquired spectrum;

subtracting the background from the fluorescent X-ray intensity of the object component by assigning S and B, which are obtained from an acquired spectrum, to a subtraction formula in which calculated values are set as α and β;

performing a correction corresponding to a composition of the sample for the fluorescent X-ray intensity obtained by subtracting the background; and

calculating a concentration of the object component in the sample on the basis of a calibration curve representing a relation between a concentration of the object component and a value obtained after performing the correction for the fluorescent X-ray intensity obtained by subtracting the background.

2. The concentration measuring method according to claim 1 , comprising steps of:

acquiring spectrums of secondary X-rays generated from a plurality of standard samples, concentrations of the object component of which have known values that are not zero;

subtracting the background from fluorescent X-ray intensities of the object component, which are obtained from the spectrums acquired for a plurality of standard samples; and

setting a correction formula for performing the correction, on the basis of a relation between concentrations of the object component related to a plurality of standard samples and fluorescent X-ray intensities obtained by subtracting the background.

3. The concentration measuring method according to claim 2 , comprising steps of:

setting a correction formula I×(B 0 /B) γ by calculating a constant γ according to a plurality of formulas obtained by assigning I k , B 0 and B k to a relation formula (wherein I k : a value obtained by subtracting the background from a fluorescent X-ray intensity of an object component obtained from a spectrum related to a k-th standard sample, B 0 : a scattered X-ray intensity obtained from a spectrum related to a specific reference sample to be a reference of a fluorescent X-ray intensity, B k : a scattered X-ray intensity obtained from a spectrum related to the k-th standard sample, and γ: a constant) expressing that a concentration C k of the object component related to the k-th standard sample is proportional to I k ×(B 0 /B k ) γ ; and

performing the correction by assigning I and B to a correction formula in which a calculated value is set as γ.

4. The concentration measuring method according to claim 1 , comprising steps of:

acquiring spectrums of secondary X-rays generated from a plurality of standard samples, concentrations of the object component of which have known values that are different from each other;

subtracting the background from fluorescent X-ray intensities of the object component obtained from a plurality of acquired spectrums;

performing the correction for values obtained by subtracting the background from fluorescent X-ray intensities related to a plurality of standard samples; and

obtaining a calibration curve representing a relation between a concentration of the object component in the sample and a value obtained after performing the correction for the fluorescent X-ray intensity obtained by subtracting the background, from concentrations of the object component related to a plurality of standard samples and values obtained after performing the correction for values obtained by subtracting the background from fluorescent X-ray intensities related to a plurality of standard samples.

5. A fluorescent X-ray spectrometer for calculating a concentration of an object component in a sample from a fluorescent X-ray intensity, comprising:

a first acquiring unit for acquiring spectrums of secondary X-rays generated by irradiating a plurality of standard samples, concentrations of the object component of which are zero and compositions of which are different from each other, with primary X-rays;

a setting unit for setting a subtraction formula by calculating constants α and β according to a plurality of formulas obtained by setting I=0 and assigning S and B, which are obtained from the spectrums acquired for a plurality of standard samples, to a subtraction formula I=S−α×B−β (wherein I: a fluorescent X-ray intensity obtained by subtracting the background, S: a fluorescent X-ray intensity of the object component obtained from a spectrum, α and β: constants, and B: a scattered X-ray intensity obtained from a spectrum) for subtracting the background from the fluorescent X-ray intensity of the object component, which is obtained from a spectrum;

an irradiating unit for irradiating the sample with primary X-rays;

a second acquiring unit for acquiring a spectrum of secondary X-rays generated from the sample;

an obtaining unit for obtaining a fluorescent X-ray intensity of the object component included in the sample from the spectrum;

a subtraction formula storing unit for storing the subtraction formula set by the setting unit;

a correction formula storing unit for storing a correction formula for performing a correction corresponding to a composition of the sample for the fluorescent X-ray intensity obtained by subtracting the background;

a calibration curve storing unit for storing a calibration curve representing a relation between a concentration of the object component and a value obtained after performing the correction for the fluorescent X-ray intensity obtained by subtracting the background;

a subtracting unit for subtracting the background from the fluorescent X-ray intensity of the object component, which is obtained by the obtaining unit from the spectrum acquired by the second acquiring unit, using the subtraction formula;

a correction unit for performing the correction for the fluorescent X-ray intensity, which is obtained by subtracting the background, using the correction formula; and

a concentration calculating unit for calculating a concentration of the object component in the sample on the basis of the calibration curve.