SU1165952A1 - Atomic fluorescence analyzer - Google Patents

Description

(21) 3696566 / 24-25.

(22) 01/31/84

(46) 07.07.85. Bksh. Number 25

(72) E.L.Altman, A.A.Taneev,

Yu.K. Evlampiev, GB Sveshnikov

and Yu.I.Turkin

(71) LSU named after A.A. Zhdanov

(53) 543.42 (688.8)

(56) 1. A. Seidel. Atomic fluorescent analysis. M., Science, 1980,

with. 105

2. Atanov A.N. et al. Highly sensitive atomic-fluorescent flame photometry with a continuous spectrum source. Journal of Applied Spectroscopy, Vol. XVII, Issue 4, 1972, p. 577 (prototype).

(54) (57) An ATOMIC-FLUORESCENT ANALYZER containing an optically coupled resonant radiation source, an atomizer, a monochromator, and a photomultiplier tube, characterized in that, in order to reduce the detection limit by increasing the selectivity, between a monochromator and a photomultiplier tube is located a vacuumized tee tube, an evacuated vacuum source and an electrolyte. filled with atomic vapors of the element being detected, and their concentration is selected from the condition that the optical density for resonant radiation is ensured. ranged within .S-IO -. The invention relates to analytical instrumentation and can be used in the analysis of the elemental composition of a substance, for the analysis of geological samples, aerosol filters and for the analysis of elements in the atmosphere. A known spectrometric instrument for fluorescence analysis of a dust sample in which a light beam with a spectral range containing the absorption wavelengths of a particular element being detected is sent to a sample. In this case, a specific spectral line is identified and determined, corresponding to one of the absorption wavelengths lj. The closest in technical essence to the proposed invention is an atomic fluorescence analyzer containing a source of resonant pulses an atomizer monochromator and a photomultiplier 2j. A disadvantage of the known device is the high detection limit due to the absence of selectivity due to the influence of nonresonant scattered radiation on the aerosol drink, air molecules and. The purpose of the invention is to reduce the detection limit of an instrument by increasing the selectivity. The goal is achieved by the fact that in an atomic fluorescent signaling device containing a source of resonant radiation, an atomizer and a monochromator and a photomultiplier between the monochromator and the photomultiplier. of the element being determined, and their concentration is chosen from the condition that the optical potential for the resonance radiation should be within the limits of SlO - 5 10. Fig. 1 shows the proposed analyzer 5 in Figs. 2 and 3 - the contours that show the operation of the analyzer; figure 4 - dependency graphs. The analyzer contains a source of 1 p resonance radiation 9, the light from which is focused by elliptical 2 and spherical 3 and 4 reflectors on the atomizer 5 (trap 6 for light 3 reduces losses) and through the hood 7 a monochromator 8 and a cell 9 filled with saturated vapors are analyzed element arrives at the photomultiplier tube (PMT) Yu, the proposed device works as follows. Resonant radiation from source 1 with the help of focusing mirrors 2-4 enters the zone 5 of sample atomization. Then the secondary radiation from the atoms of the detected element through the monochromator 8 and the cuvette 9 falls on the photomultiplier tube Yu, Cuvette 9 provides the selectivity of the analysis. Fig. 2 shows how the radiation due to the scattering of resonant radiation on air molecules, aerosols, dust, etc. is filtered out. Curve 11 (FIG. 2) shows the radiation contour of the resonant lamp 1. For example, the contour of the mercury resonance line L 254 is used. The lamp has the shape of a capillary with a diameter of 1 mm. The contour fluorescence of mercury vapors in air is depicted in curve 12. The contour is noticeably different from the contour of the radiation source due to wounding caused by the collision of the studying atom with air molecules. The contour of the nonresonant scattered radiation coincides with the contour of the curve. 11 "Curve 13 shows the transmittance for cell 9. The polarization of the absorption maxima in cell 9 coincides with the maxima of the radiation intensity of the contour of curve 11, the isotopic composition of the element is the same in the radiation source 1 and in the cell 9. Thus, in a ditch 9, almost everything is absorbed. nonresonant-scattered radiation and only part of the resonant. By selecting the excitation mode of the radiation source (for example, the supply voltage of the generator's excitation discharge) and the width of the individual components of the hyperfine structure associated with the width, as well as the thickness or temperature of the cell 9, when analyzing mercury, Toroj can be achieved by transmitting the cell 9 of nonresonantly scattered radiation will compose while the transmittance of the resonant-scattered radiation of O. O., 5 This thereby ensures a gain in the detection limit as compared to an homogeneous-fluorescence analyzer without a cuvette 9 by 50 times. 3 Curve 14 shows the contour of the resonant radiation transmitted through the cuvette 9. The proposed device cannot always give the maximum effect as compared with the known technical solution due to the spectroscopic features of specific atomic energy structures. If the broadening of the fluorescence contour is insignificant, then the same even isotope is used in the radiation source 1 and 9 of the element being determined, and is isotopic, the component of the resonant emission line must coincide with one of the components of some non-even isotope of the same element. The odd isotope must be present in the natural isotopic mixture of the element being determined. Other components of the odd isotope will then be present in the fluorescence circuit. The even isotope in cell 9 filters out non-resonantly scattered radiation. On fig.Z shows the corresponding contours - curves 15-18. The choice of the optimal value of the optical density of atoms (p (b section of resonance absorption, L52 cuvette length, n is the concentration of atoms in it) is carried out as follows. Figure 4 shows the dependences (curves 19 and 20) of the cuvette transmission - T (curve 19) (for resonant radiation of mercury 254 nm, the width of an individual component of the emission line A-5 is 0.07) and the transmittance of the resonant-scattered radiation of the nonresonant-scattering radiation;, (curve 0} of the radiated radiation I d is the optical density d of the absorption of the resonant radiation (for mercury in a vacuum, for example, and CMS L 254 nm. The optimal range is chosen from the condition that the selectivity is sufficiently high and the transmittance T is not small T 10%. As follows from figure 4, the range (, 5-102 - 5 103. With cm for mercury 540. Thus, by reducing the interference of non-selectively scattered radiation by ten times and slightly reducing the signal size, it is possible to reduce the detection limits of atoms by a factor of 10 to 50.

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