Improved recovery of fluoride in plant material using a low temperature sealed chamber digestion technique in conjunction with a fluoride ion‐specific electrode

Abstract

Abstract Seven different sample preparation methods (five ashing and fusion methods, an acid digestion method, an oxygen flask combustion method) and the AOAC extraction method (975.04) were compared with a newly developed sealed chamber digestion method for the determination of fluoride (F) in vegetation. Subterranean clover tissue was the test material. Fluoride concentration in digests was measured using a F ion‐selective electrode. The sealed chamber digestion carried out with nitric acid in Teflon chambers at 120°C for 6 hours gave the highest F concentration in the plant material and the highest recovery of added F of all methods. Tests on several types of plant material confirmed the superiority of the closed chamber digestion. The superiority of the method is attributed to the complete solubilisation of F in the sample and elimination of losses of volatile F.