Influence of the operating parameters and of the sample introduction system on time correlation of line intensities using an axially viewed CCD-based ICP-AES system
| Autor: | Marco Grotti, José-Luis Todolí, Jean Michel Mermet |
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| Rok vydání: | 2010 |
| Předmět: |
Time delay and integration
Internal standard Chemistry Analytical chemistry Repeatability Signal Atomic and Molecular Physics and Optics Standard deviation Analytical Chemistry Computational physics Inductively coupled plasma atomic emission spectroscopy Flicker noise Emission spectrum Instrumentation Spectroscopy |
| Zdroj: | Spectrochimica Acta Part B: Atomic Spectroscopy. 65:137-146 |
| ISSN: | 0584-8547 |
| Popis: | The influence of the acquisition and operating parameters on time correlation between emission line intensities was investigated using axially viewed inductively coupled plasma-multichannel-based emission spectrometry and various sample introduction systems. It was found that to obtain flicker-noise limited signals, necessary to compensate for time-correlated signal fluctuations by internal standardization, the flicker-noise magnitude of the sample introduction system, the integration time and the emission line intensity had to be considered. The highest correlation between lines was observed for ultrasonic nebulization with desolvatation, the noisiest system among those considered, for which the contribution of the uncorrelated shot-noise was negligible. In contrast, for sample introduction systems characterized by lower flicker-noise levels, shot-noise led to high, non-correlated RSD values, making the internal standard method to be much less efficient. To minimize shot-noise, time correlation was improved by increasing the emission line intensities and the integration time. Improvement in repeatability did not depend only on time correlation, but also on the ratio between the relative standard deviations of the analytical and reference lines. The best signal compensation was obtained when RSD values of the reference and analytical lines were similar, which is usually obtained when the system is flicker-noise limited, while departure from similarity can lead to a degradation of repeatability when using the internal standard method. Moreover, the use of so-called robust plasma conditions, i.e. a high power (1500 W) along with a low carrier gas flow rate (0.8 L/min) improved also the compensation. Finally, high correlation and consequent improvement in repeatability by internal standardization was observed also in the presence of complex matrices (sediment and soil samples), although a matrix-induced degradation of the correlation between lines was generally observed when using ultrasonic nebulization. |
| Databáze: | OpenAIRE |
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