Determination of bromine and fluorine via sequential vaporization of TlBr and CaF molecules from the same aliquot by high-resolution continuum source graphite furnace molecular absorption spectrometry

Abstract

This work describes the development of a multielement method for determination of bromine and fluorine, via sequential vaporization of TlBr and CaF molecules, from the same sample aliquot, using high resolution molecular absorption spectrometry. The molecular absorption of TlBr and CaF was measured at 342.9797 nm and 606.4322 nm, respectively. Studies were conducted by injecting 10 μL of sample or standard of bromine and fluorine into the graphite furnace. The source of the molecule-forming agents was 10 μL of solutions at 8.0 g L−1 of thallium and calcium, individually prepared from TlNO3 and Ca(NO3)2·4 H2O. The optimized vaporization temperatures were at 900 °C (TlBr) and 2100 °C (CaF). No chemical modifiers were used, and calibration against aqueous standard was employed. The limits of detection (LOD) were 2 ng (Br) and 0.02 ng (F). The linear ranges were 5–5000 ng (Br) and 0.5–100 ng (F). The evaluation of potentially interfering species showed no interference due to the presence of bromide over the signal for CaF or fluorine over the signal for TlBr. No interference was observed for TlBr with up to 20 μg of chlorine. However, for the CaF molecule, significant depreciation of the signal for 5 ng of fluorine was observed in the presence of 10 μg of chlorine. This interference is visually indicated by the appearance of a structured background, relative to the formation of CaCl, in the region next to CaF absorption. To verify the accuracy and performance of the proposed method, drug samples were analyzed with reported values for bromine or fluorine, sea lettuce reference material BCR 279 with informed value for bromine and road dust sample CW7 with no reported values. The determined values closely agreed with the reference values for the drugs and BCR 279 samples. However, for the road dust sample, non-spectral interference was observed. Nevertheless, the results here are promising and indicate the way to develop similar studies.