Preparation of Fluoride Standard Solution
Fluoride Standard Solution (10 ppm F):
Dissolve in water sodium fluoride previously dried at 300 °C for 12 h, equivalent to 0.442 g of NaF, and dilute to 1000.0 mL with the same solvent (1 mL = 0.2 mg F). Store in a polyethylene container. Immediately before use, dilute the solution to 20 times its volume with water.
Fluoride Standard Solution (1 ppm F):
Immediately before use, dilute fluoride standard solution (10 ppm F) to 10 times its volume with water.
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