Abstract
This study presents a novel method for fluorine quantification determination by microwave-induced plasma optical emission spectrometry (MIP-OES). Due to the low temperature of this plasma, atomic emission of fluorine could not be measured, instead CaF molecular emissions were measured by using a calcium solution mixed in the spray chamber with the sample using a T-piece. Several wavelengths were studied to find the best signal to noise ratio for fluorine determination and 530.45 nm was chosen. The limit of detection for the determination of fluorine via CaF using MIP-OES was 1.1 mg L−1. A linear response was observed over two orders of magnitude (R2 = 0.998). The developed method was applied to ten tea infusion samples from the UK and Saudi Arabia. The results were not significantly different (paired Student's t-test, p = 0.97) to the results obtained using the reference method, high-resolution continuum source graphite furnace molecular absorption spectrometry (HR-GF MAS). The total fluorine in the tea infusions varied between 2.7 and 7.8 mg L−1; all of which were above the WHO recommended level of fluoride (0.8–1.5 mg L−1) in drinking water. This method can potentially be used for total fluorine determination and might be useful for fluorine speciation analysis when coupled with HPLC.
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•Fluorine can be determined in aqueous samples using low temperature microwave induced nitrogen plasma UV–Vis emission spectrometry by formation of CaF in the plasma.•Different wavelengths were explored for linearity.•LOD of 1 mg L−1 was achieved and dynamic linear response over 2 order of magnitude.•Tea infusions were measured and all 10 samples had higher fluorine concentration than recommended by the WHO.•Accuracy was successfully checked by the use of high-resolution graphite furnace molecular absorption spectrometry.