TY - GEN A1 - Bücker, Stefan A1 - Hoffmann, Volker A1 - Acker, Jörg T1 - Determination of Fluorine by Molecular Absorption Spectrometry of AlF Using a High-Resolution Continuum Source Spectrometer and a C2H2/N2O Flame T2 - Current Analytical Chemistry N2 - 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. KW - AlF KW - fluorine determination KW - high resolution continuum source absorption spectrometry KW - molecular absorption spectrometry KW - non-spectral interference KW - diatomic molecule Y1 - 2014 SN - 1573-4110 SN - 1875-6727 VL - 10 IS - 3 SP - 426 EP - 434 ER - TY - GEN A1 - Acker, Jörg A1 - Bücker, Stefan A1 - Hoffmann, Volker T1 - The Formation of AlF Molecules and Al Atoms in a C2H2/N2O Flame Studied by Absorption and Emission Spectrometry of Molecules and Atoms T2 - Current Analytical Chemistry N2 - The absorption of the diatomic molecule AlF in the C2H2/N2O flame at 227.66 nm reveals an interesting feature. The calibration curve of the AlF absorption plotted against a rising concentration of hydrofluoric acid in solutions of constant aluminum content consists of two subsequent linear sections of different slopes. The bend position is reproducibly found at a molar fluorine-to-aluminum ratio of 3, calculated from the composition of the studied solutions. To explain this behavior, the most prominent aluminum flame species Al, AlF, and AlO were recorded as a function of the burner gas composition and flame observation height, using a high-resolution continuum source flame absorption spectrometer. As a result, the two-sectioned calibration curve is explained by two different pathways of AlF molecule formation: At a molar fluorine-to-aluminum ratio of below 3, aluminum is transported into the flame by two parallel pathways. One is the common pathway in absence of fluorine via the reduction of oxidic and/or carbidic species by the flame gases. The second pathway comprises the formation of gaseous AlF3 and its decomposition into AlF molecules and, subsequently, Al atoms. The fractionation of AlF3 releases Al atoms much faster than through the reduction of the oxidic and/or carbidic species. At molar fluorine-to-aluminum ratios of above 3, all aluminum is introduced to the flame via gaseous AlF3. A further increase of the hydrofluoric acid concentration increases the fluorine atom concentration in the flame, so that the AlF formation is determined by the recombination of aluminum and fluorine atoms. KW - AlF KW - AlF3 KW - AlO KW - diatomic molecule KW - high-resolution continuum source absorption spectrometry KW - molecular absorption spectrometry KW - molecular emission spectrometry KW - air-acetylene flame Y1 - 2014 SN - 1875-6727 SN - 1573-4110 VL - 10 IS - 3 SP - 418 EP - 425 ER - TY - GEN A1 - Acker, Jörg A1 - Bücker, Stefan A1 - Hoffmann, Volker T1 - Impact of the chemical form of different fluorine sources on the formation of AlF molecules in a C2H2/N2O flame T2 - Journal of Analytical Atomic Spectrometry N2 - The formation of diatomic AlF molecules was studied in a C2H2/N2O flame by means of a high-resolution continuum source flame absorption spectrometer using different fluorine containing compounds HF, H2SiF6, HBF4 and CF3COOH as fluorine sources. The fragmentation of these fluorine sources, as well the resulting impact on the AlF molecule formation, was derived from flame height distribution studies of the atomic and molecular species Al, AlO, Si, SiO, SiF, B and BF as a function of the fluorine concentration, the molar Al : F ratio and the burner gas composition. As a consequence, the used fluorine sources HF, H2SiF6, HBF4 and CF3COOH have been divided into two major groups. The first group of fluorine sources, covering HF, H2SiF6 and HBF4, decomposes during the drying of the aerosol under the formation of AlF3, which is the dominating species for the transport of aluminium into the flame. Its decomposition into AlF results in a high sensitivity of AlF molecular absorption at low flame observation heights. The second group of fluorine sources is exemplarily given by CF3COOH. In the upper parts of the flame the cleavage of the very stable C–F bond proceeds incompletely so that the sensitivity of the AlF molecular absorption is considerably lower than that for the other fluorine sources. In consequence, the AlF molecules are formed by the reaction between the fluorine atoms and the aluminium atoms, which are transported into the flame without the aid of fluorine, presumably via oxidic and/or carbidic species. The present investigations show that the sensitivity of the AlF molecular absorption and the pathway of AlF formation depend on the chemical form of the fluorine in the studied samples. KW - flame molecular absorption spectrometry KW - diatomic molecule KW - aluminum monofluoride KW - C2H2/N2O flame KW - hexafluorosilicic acid KW - tetrafluoro boric acid KW - trifluoro acetic acid KW - species fragmentation Y1 - 2016 UR - http://pubs.rsc.org/en/Content/ArticleLanding/2016/JA/C5JA00470E#!divAbstract U6 - https://doi.org/10.1039/C5JA00470E SN - 0267-9477 SN - 1364-5544 VL - 31 SP - 902 EP - 911 ER -