Abstract

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.

Graphical Abstract