SU1580232A1 - Method of x-ray luminescence analysis of composition of substance - Google Patents

Abstract

The invention relates to methods for fluorescent X-ray radiometric analysis of the composition of a substance and can be used in the quantitative determination of the contents of elements in samples of complex chemical composition. The aim of the invention is to improve the accuracy of the analysis when using radiation with energy, for which only one type of scattering is practically observed in the test substance. A sample of the analyte is irradiated with x-ray or gamma radiation with an energy E, such that between it and the energy of incoherently scattered radiation does not fall the energy of a single absorption edge of any of the main elements of the analyte. The intensities of the characteristic X-ray radiation of certain elements and coherently or incoherently scattered radiation are recorded. If the intensity of either coherently or incoherently scattered radiation is low, then the sample of the test substance is irradiated with radiation of another energy E 2, which, besides satisfying the condition for choosing energy E 1, is also such that for it the mass coefficients of coherent and incoherent scattering by the test substance comparable to each other. The N 2 / N 2 ratio of the intensities of coherently and incoherently scattered radiation is recorded and the value of @ or @ dl is determined by standard radiation samples with an energy E 1 from the ratio N 2 / N 2 according to the pre-built calibration dependences of the differential mass scattering coefficients @ and @ the test substance. Taking into account these values, the contents of the determined elements are found. 6 Il.

Description

The invention relates to methods for fluorescent X-ray radiometric analysis of the composition of a substance and can be used in the quantitative determination of the contents of elements in samples of complex chemical composition.

The aim of the invention is to improve the accuracy of the analysis when using radiation with energy, for which only one type of radiation is practically observed in the substance being analyzed.

FIG. Figure 1 shows the dependences of the differential mass coefficients of coherent and incoherent scatter on the intensity ratio of coherent and incoherent scattered radiation; in fig. 2 - dependences of the differential mass coefficient of coherent scattering of radiation with different energies E, on the differential mass coefficient of coherent scattering of radiation with energy E2; in fig. 3 is the same for incoherent scatter;, FIG. b - calibration dependences of the mass coefficient of coherent and incoherent scattering radiation with energy Ef on the ratio of the intensities of coherent and incoherent scattered radiation with energy in FIG. 5 - calibration dependence of zinc content on the value

fa2 d6K

n-fc-f in FIG. 6 — graduation

dependence of lead content on magnitude h1. -

ranks

N "dft

In the proposed method of X-ray fluorescence analysis, as well as in the known method, the content of the determined element is found by value

N dfr

kg

N

d6

nk

SF dJff or

magnitudes

i ™ ak 1

where N,, N to are the intensities, respectively, of the characteristic X-ray radiation of the element being detected, coherently and incoherently scattered by the analyte gamma radiation with energy E;

. , KG it NK1

t-rt, differential mass

coef fi cient and incoherently scattered radiation with energy E

In this case, the values of the mass scattering coefficients can be found (as is done in a known method) by the value of the experimentally measured T th intensity ratio

one

coherently and incoherently scattered by the analyte radiation with energy E., which serves to excite the characteristic x-ray radiation of a detectable element, according to dependencies (Fig. 1), where curve 1 shows the dependence

d &

kg

N

kg

d6

nk

a (y, -, and t v „„ a e. dSf f (a CURVOINT 2 dfl

N CG - a (). This known method

finding mass coefficients

dissipated is feasible if between the energy E1 and the energy of incoherently scattered radiation there is no energy of any of the main elements of the analyte and the energy E is sufficiently far from the energy of the absorption edge of the main and detectable elements so that anomalous scattering does not affect, and also if the differential mass coefficients are d6T d6HK

The factors are scattered and comparable in magnitude. If the latter condition is not met, then one of the peaks of scattered radiation in the spectrum is practically absent, and the error oAi. KG

do 1

Definitions -: - „- or unacceptable d SJ d il

is great.

However, there is a definite analytical relationship between the differential mass scattering coefficients of radiations with different energies. Therefore, the determination of mass scattering coefficients by the same method is possible if the irradiation of the analyte is carried out with radiation with an energy of E2, for which both scattering processes have average kgj

dbtd bg

Attention values:, - massive

d md it

scattering coefficients. The energy E2 must satisfy the formulated conditions for the selection of the radiation energy used to determine the mass scattering coefficients.

As evidence of the uniqueness of the dependencies between the differential mass coefficients

For various radiation energies (Figs. 2 and 3), the calculated dependences are given.

d & i d6 2

dSf ° T dlf

for E, 11.22 keV and E 22.16 keV

(curve 3)

and E. 17.48 keB and Er 22.16 keV

  t

(curve 4)

NK

j, kk,

About 6 1 a & g.

Dd from an

for E 59.6 keV and Et 22.16 keV (curve 5)

and E, 122 keV and Еg 22.16 keV (curve 6).

The method is carried out as follows.

A sample of the analyte is irradiated with an x-ray or gamma-ray flux with energy E, and the quanta fluxes of the characteristic x-ray emission of the element being detected N and coherent

scattered

N g or incoherent Mnk

primary radiation and calculate from NN wearing - & - or - "-" -.

Y4

Then a series of standard samples with different and known elemental composition, simulating the entire possible range of changes in the material composition of the analyte, is prepared. They are irradiated with a flux of x-rays or gamma rays with an energy Eg and the fluxes of quanta of coherently mogy incoherent radiations are recorded.

The values of differential mass coefficients of coherent and incoherent scattering of standard radiation samples with energy E1 are calculated by the substance and the calibration dependencies are calculated

d6V N $ r. d & r f, NK / dft Md6 - f (Nr-}

Then, the test sample is irradiated with X-ray or gamma radiation.

N Јcraces energy E,

soscience coherently real N

and record inte-ny and necogen

Excessive radiation.

N CG is the GL ratio for the d6f ..NT study.

my samples and schedule n f (

N

BUT ""

a to i,. , h á -.

or - "- f (FFrK-),

determine the value of the mass dissipation factor with energy E, which is used

five

0

five

0

five

are used to calculate the content of the element being determined, taking into account the calibration dependence

C f (

N d6

KG

OR

dfi

J-

,,,, NK

Example 1 By the proposed method, the zinc content in the control samples with known values of the elemental contents is determined, the zinc content in them varies from 0.9 to 19.2%, lead from 0.03 to 5.48%, BaS04 from 1.34 Up to 81.34%.

The characteristic x-ray radiation of zinc is excited by radiation (E 11.22 keV) of a selenium target irradiated by radiation of a 0.005BH-1 low-power x-ray tube with a molybdenum anode. For measuring the differential mass coefficient of coherent scattering, radiation from a cadmium-109 radionuclide source with energy Еg 22.16 keV, activity 10 mCi is used. Secondary radiation is detected by a silicon lithium semiconductor detector with a resolution of 200 eV along the line of 5.9 keV.

The voltage applied to the tube is 35 kV at a filament current of 80 µA. Geometric angles of incidence of primary radiation and selection of secondary radiation are 30 and 90 °, respectively. Measurements are carried out on a 1024-channel analyzer with an observation time of 400 s.

A series of standard samples of chemically pure reagents of silicon, calcium, barium, zinc, lead and BaSOx is prepared, for which mass coefficients of coherently scattered radiation with an energy of Ep 11.22 keV are calculated at a scattering angle of 0 120 ° according to the following Formula in cm2 / g):

A / kg

 i

  (° 571 Co + 1478 CS, + B858 C5 +

 2,711

cc "+

4,901 Czn + 9,968 Ave) x

x S-2

where SL, S,

WITH,

C in - C ° 0 S, S l Coi 2 g. holding in standard samples oxygen, silicon, sulfur, calcium, zinc and barium, respectively.

Measurement of standard samples and analytes crushed to 200 mesh is carried out in cuvettes with a diameter of 26 mm and a height of 6 mm. Calibration dependence

,, KG .., K.G

ac 1, n 2

  (Pnc) is given as curve 7 (fig. F).

The analytes are then irradiated with characteristic X-rays of selenium with an energy Ej of 11.22 keV, and the intensities of the characteristic emission of zinc N2 (in the part of the spectrum, COOT-corresponding K-line) and coherently scattered KL-radiation of the selenium target and the calculated yt attitude

N

2n

fjTTr intensity is characteristic

radiation of zinc to the intensity of coherently scattered primary radiation. Then the samples of the analyzed substances are irradiated with a flux of quanta of the radiation of the cadmium-109 radioisotope with an E2 energy of 22.16 keV, the fluxes of quanta are recorded coherently Ng and incoherently N N to the scattered radiation, the ratio

and according to the calibration schedule

(Fig. A, curve 7) determine the values of the mass coefficient of the coherently scattered radiation of the analytes for energy E (11.22 keV. The values obtained are multiplied by

m KG

N 1

„N

2n

s-k relationship values found

and 1 and calibration dependencies

N d is Kr C r f (jprr-) constructed by

The results of measurements of samples with certified values of zinc contents, zinc contents are found in. samples of the analyzed substances. The measurement results are plotted on a graduation chart (Fig. 5).

Example 2. The proposed method determines the lead content in the same samples as in example 1. The same standard samples are used. The K-series of lead is excited by gamma radiation from a cobalt-57 source with energy E., 122 keV. To determine the incoherent scattering mass coefficient, the radiation from a cadmium-109 source with an E4 energy of 22.16 keV is used. Detektiro

secondary radiation is realized. are on the same setup.

1 Standard measurements were carried out in cuvettes with a diameter of 26 mm and a height of 6 mm. Constructed by measurement results Graduated

five

mk, N 2

P

with

dependence --Ј- f (- H) is given

in view of curve 8 (fig. k).

Measurement of samples of the analyte is carried out in conditionally thin layers with a surface density of 0.08 g / cm, ensuring the independence of the measurement results from differences in the absorption characteristics of the studied samples. The sample under study is irradiated with a cobalt-57 radionuclide with an energy of E of 122 keV, and the intensities of the characteristic radiation of lead N pb (in the part of the spectrum corresponding to Kalinin) and incoherently scattered primary radiations of N c and

calculate intensity ratio NPb

 Then, a sample of the test substance is placed in a cuvette with a diameter of 26 mm and a height of 6 mm, irradiated with a flux of quanta of the radioisotope of cadmium-109, recorded fluxes of quanta coherently N g and incoherently

Nnh ... and

j of scattered radiation with energy

E4 22.16 keV, calculate ratio

N 4G

 and on schedule (Fig. 4, curve 8)

and j

determine the value of the mass coefficient d6

nk

0

tsenta - incoherently scattered

analyte radiation with an energy of & and 122 keV. Received

d6H

value multiplied by found

relation and graduation

the graph (Fig. 6), constructed from measurements on samples with certified lead contents, determines the lead content in the test substance. The measurement results are plotted on a calibration curve (Fig. 6).

In examples 1 and 2, the known method does not allow to obtain acceptable results, since the intensities of coherently and incoherently scattered radiations with the energy En, most suitable for exciting the characteristic radiation of the element being detected, are not comparable in magnitude.

Using the proposed method of analysis allows several times to increase the accuracy of measuring the contents of the determined elements.

Claims (1)

Invention Formula The method of X-ray fluorescence analysis of the composition of a substance consisting in irradiating a sample of an analyte with x-ray or gamma radiation with energy Ef selected from the condition that no absorption edge of any of the main elements of the analyte gets between the energy of the incoherently scattered radiation detecting the intensities of characteristic X-ray radiation of detectable elements, coherently or incoherently scattered radiation of a sample, determining the differential mass   R coherent coefficients: - „- or d6 - d I incoherent radiation scattering by the analyte and finding the contents of the determined elements taking into account the values of the ratio of measured intensities and the found differential mass scattering coefficient, characterized in that, in order to improve the accuracy of the analysis when using 08 16 2.4 3.2 b, 0 one . i Radiation with energy, for which only one type of scattering is practically observed in the analyzed substance, the sample of the analyte and a set of standard samples with different and known composition are additionally irradiated with X-ray or gamma radiation with energy E satisfying the condition for choosing energy E and the additional condition which implies that for it the differential mass coefficients of coherent and incoherent scattering by the analyte are comparable with each other, the intensities are recorded coherent kg the coherence values of N "n" tno N Ј scattered radiation, calculate the mass coefficients cohe, d6 "rd6KK rental --- and incoherent d 51d J2 radiation scattering with energy E, the substance of standard samples, strod6 kg U (J 1 - t calibration dependencies --v- ea CT GJ A KG kg kg  f (-2--) chad nk 1 l IC ., 9 f / ilJL- i And dfl f (N "K} According to the results of measuring the intensity ratio coherently and incoherently scattered by standard samples of radiation with energy E, the value of the required mass scattering coefficient of the analyte of radiation with energy E f is determined by the value of the ratio of intensities coherently and incoherently scattered by the analyzed substance radiation with energy E Rel-ed / U / 7 / UL Fig, 1 ezhnsho  ft Z 94 80 ЈVPf zOl tSP / J P Z L II 01 6V B Q „L 1gpF zOtxlSP / jfcp g / gy ti Z 01 9 i Z l 80 W , B 0 OC $ OL vw t UP W h r $ 2 20851 0.5 $ I and pc B "and I YU 12 With gp,%