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Comparison of the thermodynamic and correlation criteria for internal standard selection in Laser-Induced Breakdown Spectrometryтезисы доклада
- Авторы: Labutin T.A., Zaytsev S.M., Seliverstova I.V., Popov A.M.
- Сборник: Book of Abstracts of 7th International Conference On Laser-Induced Breakdown Spectroscopy "LIBS-2012", 29 September - 4 October, Luxor, Egypt
- Тезисы
- Год издания: 2012
- Место издания: Luxor, Egypt
- Первая страница: 115
- Последняя страница: 115
- Аннотация: The majority of precise quantitative analytical techniques using emission spectra are based on some variant of the internal-standard principle. The spectral line used as an internal standard should compensate for pulse-to-pulse variations in evaporated mass and excitation conditions. There is the general criterion (thermodynamic) of closeness of upper level energies, but really it describes requisite condition resulting from excitation of atoms in laser plasma. Because of the transfer of species from condense phase into the plasma, an ambient atmosphere may influence analytical signal more than excitation conditions in plasma. Though the thermodynamic criterion is enough in many cases and provides a good result with the selected line of matrix element, while in others the final result is worsened. Unfortunately there is a very lack of investigations on establishing criteria for internal standard selection. Obviously, it is necessary to have additional criteria to select proper internal standard. Application of internal standard means that intensities of reference and analytical line are both related to the fluctuated parameters. To avoid rigorous estimation of this relation based on the model of ablation process (that is practically impossible), the efficiency of the diminishing of the fluctuations influence on calibration can be studied by the correlation strength between intensities of analytical and selected reference lines. We tested the use of correlation strength as a criterion for reference line selection in LIBS analysis of high alloy steels and soils. For each pixel of spectrum, the correlation value between the corresponding signal intensity and the analytical line intensity (Mn, Si, Zn, Be lines) was obtained over 60 plasma spectra recorded for different energy of laser. If reference line with R>0,8 was chosen, normalization by the intensity of this reference line provided improving of calibration graph. All selected reference lines also fulfilled thermodynamic criteria. Thus, the study of correlation between analytical and reference lines can provide the easy and accurate choice of normalization strategy that gives assured improvement of the figures-of-merit. Another advantage of “correlation approach” is that no spectral line parameters (even wavelength) are needed and only experimental data are involved in the reference line selection.
- Добавил в систему: Лабутин Тимур Александрович