Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Patent
1995-10-30
1998-04-21
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
G01N 2174, G01N 2131
Patent
active
057423881
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to optical instruments engineering and may be used when developing atomic absorption (AA) spectrophotometers with electrothermal atomizers.
BACKGROUND ART
At present, Atomic Absorption Spectrometry with electrothermal atomization is one of the most developed methods of determination of trace quantities of more than 60 elements in a variety of substances and materials. High sensitivity, selectivity and precision are characteristic of the method. An inherent feature of this method of analysis is non-stationarity of the analytical signal. All modern spectrophotometers record it with high temporal resolution; however, the signal recorded by a photomultiplier tube (PMT) at the instrument output is essentially an integrated characteristic of analytical volume as a whole and lacks spatial resolution. In the case of a uniform distribution of analyte atoms in the atomizer volume this causes no problems. However, as the imaging of analytical volume has shown, the atoms and molecules of the element to be determined may be distributed within the electrothermal atomizer extremely V. Voloshin. Shadow Spectral Filming: A method of investigating Electrothermal Atomization. Part 1. Dynamics of Formation and Structure of the Absorption Layer of Thallium, Indium, Gallium and Alluminium Atoms.//Journ. Anal. Atom. Spectrometry, 1991, v. 6, p.505-519, (2) A. Kh. Gilmutdinov, Yu. A. Zakharov, V. P. Ivanov, A. V. Voloshin and K. Dittrich. Shadow Spectral Filming: A method of investigating Electrothermal Atomization. Part 2 Dynamics of Formation and Structure of the Absorption Layer of Tallium, Indium, Gallium and Alluminium Molecules.//Journ. Anal. Atom. Spectrometry, 1992, v. 6, p. 675-683.!. On Abdullina, S. F. Gorbachev and V. L. Makarov. Formation of Analytical Signal in Electrothermal Atomic Absorption Spectrometry. Influence of temperature and concentration gradients.//Zhurn. Analit. Khimii, 1991, v. 46, p. 1480-1492.! shows that the analytical signal recorded at the spectrophotometer output depends not only on the number of absorbing atoms, but also on their distribution over the atomizer cross-section. This leads to two limitations in the existing detection systems. First, the relation between the absorbance recorded at the spectrophotometer output and the number of absorbing atoms proves to be ambiguous. Second, analytical curves appear to be largely curved in the region of high
Thus, the use in an AA spectrophotometers of a detection system having no spatial resolution leads to narrowing of the range of concentrations to be measured due to curvature of analytical curves and to the increase of measurement error due to the ignored influence of absorption layers inhomogeneity. Therefore, to obtain a correct analytical signal, it is necessary to have a detection system ensuring not only sufficient temporal but also spatial resolution.
There exist a detection system of a AA spectrophotometer with a linear M. Harnly. Continuum Source Atomic Absorption Spectrometry with a Pulsed Source a Photodiode Array Detector.//Journ. Anal. Atom. Spectrometry, 1989, v. 4, p. 673-674.!. In such a system the photodiode detector is positioned along the spectral instrument dispersion and besides the resonance line also records the radiation of adjacent lines.
However, such an arrangement of the photodiode array detector offers no possibility to use it for spatially resolved recording of the analytical signal. Therefore, such spectrophotometers have no spatial resolution and suffer from the drawbacks similar to the above shortcomings inherent in detection systems based on the use of photomultiplier tubes.
SUMMARY OF THE INVENTION
The object of the invention is to improve the analytical performance of an AA spectrophotometer, namely, lower its detection limits, extend the range of concentrations to be measured, increase the reproducibility of measurements by taking into account the temporal and spatial non-uniformities of the analyte distribution over the atomizer volume and simultaneous measur
REFERENCES:
patent: 4339201 (1982-07-01), Yaduda
patent: 4544271 (1985-10-01), Yamamoto
Journ.Anal.Atom.Spectrometry,1992,v.6,pp. 675-683. A.KH.Gilmutdinov,YuA.Zakharow, V.P.Ivanov,A.V.Voloshin & K.Dittrich. Shadow Spectral Filming: A Method of Investigating Electrothermal Atomization.Part 2 Dynamics of Formation & Structure of Absorption Layer of Tallium,Indium,Gallium & Alluminium Molecules. Zhurn.Analit.Khimii,1991,v.46,pp. 1480-1492.
A. Kh. Gilmutdinov,T.M. Abdullina,S.F. Gorbachev and V.L.Makarov. Formation of Analytical Signal in Electrothermal Atomic Absorption Spectrometry.Influence of temperature and concentration gradients. (English translation only) Journal of Analytical Chemistry, v.46, No. 8, Feb. 2, 1992 pp. 1073-1082.
Atom.Spectrometry, 1989,v.4,pp. 673-674. Gary P. Moulton, Thomas C. O'Haver, James M. Harnly. Continuum Source Atomic Absorption Spectrometry with a Pulsed Source a Photodiode Array Detector.
Spectrochimica Acta,Part B:Atomic Spectroscopy,vol. 38 B, No. 7, 1983, Oxford,GB pp. 987-993, Gary D. Rayson et al. "Spatially Resolved Arrhenius Determinations Within A Graphite Furnace Atomizer" see pp. 989-990 Figs. 1-3.
Analytical Chemistry, vol. 57, No. 11, Sep. 1985, Columbus US pp. 2049-2055 John W. Olesik et al. "Optical Imaging Spectrometers" see p. 2050, left column, line 36-line 38.
Applied Optics, vol. 21, No. 7, 1 Apr. 1982, NewYork US pp. 1236-1240, M.Alden et al. "Single-Pulse Laser-Induced OH Fluorescence In An Atmospheric Flame, Spatially Resolved With A Diode Array Detector" see p. 1236,right column, line 8-line 18; fig. 1.
Applied Spectroscopy,vol. 31, No. 6,1977, Baltimore US pp. 536-541, T.E. Edmonds et al. "Spatial Profiles of Emission From An Inductively Coupled Plasma Source using A Self-Scanning Photodiode Array", see p. 536, left column, line 1-4--line 41-44.
Journal of Analytical Atomic Spectrometry, vol. 6,Oct. 1991,GB pp. 505-519, Albert KH. Gilmutdinov et al."Shadow Spectral Filming:A Method of Investigating Electrothermal Atomization,Part 1.",Cited in application--see p. 506,left column, line 61-63, see p. 508, right column, line 5-15.
Gilmutdinow Albert H.
Nagulin Konstantin J.
Aker David
Bodenseewerk Perkin-Elmer GmbH
Evans F. L.
Grimes Edwin T.
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