Optimal Conditions for Determination of Fluoride in Plant Samples by Microwave Digestion Coupled with Ion Selective Electrode Method

It is helpful to predict the ecological and environmental effects of fluoride by accurately detecting the fluorine content in plants. Fluoride in plant samples is commonly lower than 300 μg/g. The chemical separation method with good separation effect should be selected to avoid the loss of F and determine the resulting solution with simple components and low blank when the method of microwave digestion coupled with Ion Selective Electrode Method is applied. Appropriate buffer solution is added to increase the intensity of fluoride ions and reduce screen interferences. Plant samples are digested by microwave, and fluoride is determined by Ion Selective Electrode Method, as reported in this paper. The concentration of buffer solution is defined by optimal conditions. Results show that the addition of 10 mL TISABⅡ solution of 147 g/L to the sample solution at 25℃ and pH of 6.5 can avoid the formation of stable insoluble floccule due to the reaction between cation and fluoride ions. The method has a relative standard deviation (RSD) of less than 8.5%, a detection limit of 0.242 μg/g and a recovery of 92.0%-108%, which meets the determination requirement of the low-content fluoride in plant samples.