Determination of Fluorine by Molecular Absorption Spectrometry of AlF Using a High-Resolution Continuum Source Spectrometer and a C2H2/N2O Flame
Stefan Bucker, Volker Hoffmann and Jorg Acker
Affiliation: Brandenburg University of Technology Cottbus-Senftenberg, Faculty 6: Natural Sciences, Department of Chemistry, Großenhainer Straße 57, D-01968 Senftenberg.
The molecular absorption of the diatomic AlF molecule in the C2H2/N2O flame was studied using a highresolution
continuum source flame atomic absorption spectrometer.
AlF has a structured absorption spectrum in the range of 227.30 nm and 227.80 nm. From this band system, the remarkably
narrow absorption band at 227.66 nm proved to be the optimum for analytical purposes. The signal intensity was studied
as a function of the C2H2 : N2O ratio, the aspiration flow, and the aluminum concentration added to the analytical solution
to generate the AlF molecules in the flame. The AlF molecule formation is significantly affected by the bonding state
of the fluorine source used. Compared to ionic bound fluorine, organic bound fluorine leads to a markedly less sensitive
molecular absorbance of AlF. Furthermore, several ions, such as Na+, K+ and NH4+
+, and acids, such as HCl, CH3COOH,
and HNO3, affect the AlF signal intensity severely. It has to be concluded that the determination of fluorine by AlF F
MAS only leads to reliable analytical results in simple matrices.
Keywords: Aluminum monofluoride (AlF), fluorine determination, high resolution continuum source absorption spectrometry,
molecular absorption spectrometry (MAS), non-spectral interference.
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