Determination of fluorine in plant materials via calcium mono-fluoride using high-resolution graphite furnace molecular absorption spectrometry with direct solid sample introduction
A method has been developed for the determination of fluorine in plant materials using high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) and direct solid sample analysis with calibration against aqueous standard solutions. The diatomic molecule CaF has been selected as the target molecule as it has been considered to provide more favorable conditions for this application compared to other diatomic molecules described in the literature. Using only 15 μg Ca as the molecule-forming reagent, it was possible using a pyrolysis temperature of 900 °C and a vaporization temperature of 2000 °C, values that are distinctly different from published values, to obtain a much better sensitivity (m0 = 44 pg) and limit of detection (36 pg absolute or 0.36 μg g−1 for solid samples) compared to values published using the same target molecule. Two certified reference materials have been analyzed to confirm the accuracy of the proposed method. Several plant materials have been analyzed to confirm the applicability of the method to real samples; the concentrations were found to be between 2.7 and 29 μg g−1 F. It is obvious that HR-CS GF MAS is a new technique, which is not yet well explored, and which will require a lot more research to be well understood.