Sodium Fluoride Tablets

Definition

Sodium Fluoride Tablets contain Sodium Fluoride.

The tablets comply with the requirements stated under Tablets and with the following requirements.

Content of sodium fluoride, NaF

90.0 to 110.0% of the stated amount.

Identification

A. Shake a quantity of the powdered tablets containing 5 mg of Sodium Fluoride with 5 mL of water for 5 minutes and filter (Solution A). To 2 mL of the filtrate add 0.2 mL of a freshly prepared mixture of equal volumes of alizarin S solution and zirconyl nitrate solution. A yellow colour is produced.

B. Solution A yields reaction A characteristic of sodium salts, Appendix VI.

Uniformity of content

Tablets containing less than 2 mg and/or less than 2% w/w of Sodium Fluoride comply with the requirements stated under Tablets using the following method of analysis. Carry out Method I for potentiometric determination of ionic concentration using ion-selective electrodes, Appendix VIII E, using a fluoride selective electrode.

Prepare and store all solutions in plastic containers.

For solution (1) add a sufficient quantity of water to one tablet to produce a solution containing 0.0055% w/v of Sodium Fluoride, heat at 80° and mix with the aid of ultrasound until dissolved, cool to room temperature and filter. Solutions (2), (3), (4) and (5) contain 0.0110% w/v, 0.00550% w/v, 0.00220% w/v and 0.00110% w/v of sodium fluoride respectively. To 15 mL of each solution add 20 mL of a buffer solution prepared by mixing 57 mL of glacial acetic acid, 58 g of sodium chloride and 4 g of cyclohexylenedinitrilotetra-acetic acid in 500 mL of water, adjusting the pH to 5.2 with a 50% w/v solution of sodium hydroxide and diluting to 1000 mL with water.

In turn, stir each solution, immerse the electrodes and allow to stand for 5 minutes with constant stirring. Determine the potential difference between the electrodes for solutions (2), (3), (4) and (5) and plot on semi-logarithmic graph paper the potential difference obtained for each solution as a function of concentration of sodium fluoride. Using exactly the same conditions, determine the potential difference obtained with solution (1) and calculate the content of sodium fluoride in each tablet.

Assay

For tablets containing less than 2 mg and/or less than 2% w/w of Sodium Fluoride

Use the average of the individual results obtained in the test for Uniformity of content.

Labelling

The label states the quantity of sodium fluoride and of fluoride ion per tablet.