Improvement of distillation system for the determination of fluoride in soil

The aim of the present study is the optimization of a distillation system to effectively extract fluoride ions () in the form of hydrofluoric acid from soil, a complex matrix. The soil matrices were treated using the alkali fusion method with Na 2 CO 3 :ZnO:Li 2 B 4 O 7 (ratio 7:2:1 w:w:w) at 800 °C for 2 h. The pretreated sample containing fluoride ion was subjected to a distillation process in sulfuric acid, which was facilitated by argon (50 mL min −1 ) as a carrier gas and water (1 mL min −1 ) as a “steam buffer” to maintain the distillating solution at 150 °C. The distilled fluoride ion was analyzed using an ion‐selective electrode and ion chromatography (IC‐CD) methods. Quantitative recovery of fluoride ions through the distillation was achieved (97%–103%) for soil samples. The use of water as a “steam buffer” minimized the co‐distillation of sulfate ions, facilitating the analysis of fluoride in the distillate with IC. The method was successfully applied to analyze the total fluoride ions in soil following sample treatment using the alkali fusion method.