Exploring the potential of hydride generation atomic fluorescence spectrometry for ultratrace elemental analysis
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| Year of publication | 2024 |
| Type | Conference abstract |
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| Description | The non-dispersive arrangement of atomic fluorescence spectrometry (AFS) is very simple and sensitive. It can provide extremely low limits of detection (LOD) and is cheap both in investment and in operation costs. The fundamental drawback of AFS is that it is affected by scattering and quenching problems, which are not easy to control. The potential of AFS to reach very low LODs can be fully achieved when using very mild atomization conditions which are compatible with the atomization of volatile species. This is the reason why AFS is currently associated prevalently with hydride generation (HG). Our long-term ambition is the development of HG AFS for ultratrace element determination. To approach this target, we have been optimizing individual components of our laboratory- made non-dispersive atomic fluorescence spectrometer. The history of our investigations of the two essential components of a non- dispersive atomic fluorescence spectrometer, hydride atomizers and atomic lamps, will be outlined. The miniature diffusion flame (MDF) is a standard hydride atomizer for AFS. We extensively studied advantages and limitations of this atomizer. The results motivated us to develop a new atomizer - flame-in-gas shield (FIGS) which is basically an argon shielded oxygen-hydrogen microflame. Compared with MDF, it is more complicated in construction as well as in operation but it offers better sensitivity and LOD and much greater potential for miniaturization. Employing spatially resolved laser induce fluorescence, we determined distributions of temperature, hydrogen radicals and free analyte atoms in both atomizers. This made us possible to discover the mechanism of hydride atomization in MDF as well as in FIGS. Regarding atomic lamps, mainly two their types have been used: electrodeless discharge lamp (EDL) or boosted-discharge hollow cathode lamp. EDLs are said to provide higher radiation intensities, however, the range of elements for which the EDLs are manufactured is limited to certain volatile elements. Boosted- discharge hollow cathode lamps are widely applied in the current commercial AFS instruments whereas EDLs are usually used in experimental laboratory setups of AFS. The relevant lamp settings are namely: atomic lamp input power/current and its modulation pattern. In principle, the intensity of the fluorescence radiation is proportional to the radiation source intensity. Consequently, higher sensitivity and lower LOD can be reached simply by increasing the intensity of the radiation source. Our latest research on atomic lamps focusing on the absolute intensity of the lamp radiation will be presented. The positive impact of optimizations of the relevant lamp settings will also be illustrated. The potential of further development of HG AFS in terms of pushing down LODs of hydride forming elements will be outlined. |
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