Solvent extraction of trace amounts of fluoride prior to, mainly, spectrometry—a review: recent advances in the Alizarin Fluorine Blue approach

Methods for the solvent extraction of very small amounts of fluoride, usually prior to gas chromatography or absorptiometry, have been reviewed. Additionally the Alizarin Fluorine Blue–lanthanum procedure has been further developed in order to allow the determination of about 1 µg of fluoride in 500 cm3 of water with good precision. Although the method is time-consuming, it yields a detection limit for fluoride of 40 ng l–1 and a relative standard deviation (at 4 µg of fluoride) of 0.60% with the use of only very basic apparatus. The sensitivity (0–10 µg of fluoride in 500 cm3 of water) is 0.176 A µg–1(using cells with a pathlength of 4 cm).