Combination of the ionic-to-atomic line intensity ratios from two test elements for the diagnostic of plasma temperature and electron number density in Inductively Coupled Plasma Atomic Emission Spectroscopy

Year: 2007

Authors: Tognoni E., Hidalgo M., Canals A., Cristoforetti G., Legnaioli S., Salvetti A., Palleschi V.

Autors Affiliation: Istituto per i Processi Chimico-Fisici, Area della Ricerca del Consiglio Nazionale delle Ricerche Via Moruzzi 1, 56124 Pisa, Italy;
Departamento de Química Analítica, Nutrición y Bromatología. Universidad de Alicante. Apdo. 99, 03080, Alicante, Spain

Abstract: In Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) spectrochemical analysis, the MgII(280.270 nm)/MgI(285.213 nm) ionic to atomic line intensity ratio is commonly used as a monitor of the robustness of operating conditions. This approach is based on the univocal relationship existing between intensity ratio and plasma temperature, for a pure argon atmospheric ICP in thermodynamic equilibrium. In a multielemental plasma in the lower temperature range, the measurement of the intensity ratio may not be sufficient to characterize temperature and electron density. In such a range, the correct relationship between intensity ratio and plasma temperature can be calculated only when the complete plasma composition is known. We propose the combination of the line intensity ratios of two test elements (double ratio) as an effective diagnostic tool for a multi-elemental low temperature LTE plasma of unknown composition. In particular, the, variation of the double ratio allows us discriminating changes in the plasma temperature from changes in the electron density. Thus, the effects on plasma excitation and ionization possibly caused by introduction of different samples and matrices in non-robust conditions can be more accurately interpreted. The method is illustrated by the measurement of plasma temperature and electron density in a specific analytic case. (C) 2007 Elsevier B.V. All rights reserved.


Volume: 62 (5)      Pages from: 435  to: 443

More Information: Generalitat Valenciana. Ministerio de Ciencia y Tecnología, MICYT. Ministry of Education and Science, MES, CTQ2005-09079-C03-01/BQU. Ministry of Education and Science, MES, PTR1995-0882-OP-01-02. – The authors would like to thank Jean Michel Mermet for his critical insight and helpful comments on the manuscript. M. Hidalgo thanks the financial support of the Spanish Ministry of Science and Technology, Generalitat Valenciana and University of Alicante (Ramón y Cajal Program). This work has been partially supported by the Spanish Ministry of Education and Science (Projects n.: PTR1995-0882-OP-01-02 and CTQ2005-09079-C03-01/BQU).
KeyWords: ICP; Ionization equilibrium; Lines intensity ratio; LTE; Matrix effect; Plasma temperature; Robust conditions
DOI: 10.1016/j.sab.2007.05.006

Citations: 33
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