A simple and low-cost method for fluoride analysis of plant materials using alkali extraction and ion-selective electrode.

Backgrounds: Existing methods for fluoride (F) determination in plant material require expensive equipment and specialized reagents. This study aimed to develop a simple and cost-effective method for fluoride analysis in plant samples.

Results: Using an orthogonal assay design with certified reference material, this study optimized a sodium hydroxide extraction method (5 mol·L) with heating at 120 °C for 0.5 h, followed by the addition of potassium acetate, ionic strength adjustment, and measurement via an ion-selective electrode. The method achieved a limit of detection (LOD) and limit of quantification (LOQ) of 1.41 and 4.71 mg·kg⁻¹, respectively. Recovery rates ranged from 84.74 to 89.34% in Arabidopsis thaliana (intraday relative standard deviation [RSD] ≤ 2.31%, inter-day RSD ≤ 4.17%) and from 83.53 to 91.55% in Camellia sinensis (intraday RSD ≤ 3.11%, inter-day RSD ≤ 4.98%). In A. thaliana cultivated in NaF-dosed (500 µM) nutrient solution, the fluoride concentration in the shoot was 16.00 mg·kg; In C. sinensis grown under 250 µM NaF treatment, the shoot fluoride concentration was 292.71 mg·kg. Moreover, the fluoride concentration in Tea products purchased from local supermarkets ranged from 16.28 to 61.78 mg kg.

Conclusion: This study presents a simple, reliable, and cost-effective method for fluoride analysis in plant materials, which can be further validated through inter-laboratory testing to establish a standardized approach.