(Ph. Eur. monograph 0190)
NaBr 102.9 7647-15-6
DEFINITION
Content
98.5 per cent to 101.0 per cent (dried substance).
CHARACTERS
Appearance
White or almost white, granular powder or small, colourless, transparent or opaque crystals, slightly hygroscopic.
Solubility
Freely soluble in water, soluble in ethanol (96 per cent).
IDENTIFICATION
A. It gives reaction (a) of bromides (2.3.1).
B. Solution S (see Tests) gives reaction (a) of sodium (2.3.1).
TESTS
Solution S
Dissolve 10.0 g in carbon dioxide-free water R and dilute to 100 mL with the same solvent.
Appearance of solution
Solution S is clear (2.2.1) and colourless (2.2.2, Method II).
Acidity or alkalinity
To 10 mL of solution S add 0.1 mL of bromothymol blue solution R1.
Not more than 0.5 mL of 0.01 M hydrochloric acid or 0.01 M sodium hydroxide is required to change the colour of the indicator.
Bromates
To 10 mL of solution S add 1 mL of starch solution R, 0.1 mL of a 100 g/L solution of potassium iodide R and 0.25 mL of 0.5 M sulfuric acid and allow to stand protected from light for 5 min. No blue or violet colour develops.
Chlorides and sulfates
Liquid chromatography (2.2.29).
Test solution (a): Dissolve 0.400 g of the substance to be examined in 50 mL of water for chromatography R and dilute to 100.0 mL with the same solvent.
Test solution (b): Dilute 25.0 mL of test solution (a) to 50.0 mL with water for chromatography R.
Reference solution (a): To 25.0 mL of test solution (a) add 1.0 mL of sulfate standard solution (10 ppm SO4) R and 12.0 mL of chloride standard solution (50 ppm Cl) R and dilute to 50.0 mL with water for chromatography R.
Reference solution (b): Dilute 10 mL of test solution (a) to 100 mL with water for chromatography R. To 2 mL of this solution add 8 mL of chloride standard solution (50 ppm Cl) R and dilute to 20 mL with water for chromatography R.
Blank solution: water for chromatography R.
Column:
— size: l = 0.25 m, Ø = 2 mm;
— stationary phase: strongly basic anion-exchange resin for chromatography R2 (13 μm).
Mobile phase: Dissolve 0.600 g of potassium hydroxide R in water forchromatography R and dilute to 1000 mL with the same solvent.
Flow rate: 0.4 mL/min.
Detection: Conductivity detector equipped with a suitable ion suppressor.
Injection: 50 μL of test solution (b), reference solutions (a) and (b) and the blank solution.
Run time” 2.5 times the retention time of bromide.
Retention time; Chloride = about 5 min; bromide = about 8 min; sulfate = about 16 min.
System suitability: Reference solution (b):
— resolution: minimum 8.0 between the peaks due to chloride and bromide.
Calculation of percentage contents:
— for chlorides, use the concentration of chloride in reference solution (a); correct the area of the peak due to chloride in the chromatogram obtained with reference solution (a) by subtracting the area of the peak due to chloride in the chromatogram obtained with test solution (b);
— for sulfates, use the concentration of sulfate in reference solution (a); correct the area of the peak due to sulfate in the chromatogram obtained with reference solution (a) by subtracting the area of the peak due to sulfate in the chromatogram obtained with test solution (b).
Limits:
— chlorides: maximum 0.6 per cent;
— sulfates: maximum 0.01 per cent.
Iodides
To 5 mL of solution S add 0.15 mL of ferric chloride solution R1 and 2 mL of methylene chloride R. Shake and allow to separate. The lower layer is colourless (2.2.2, Method I).
Iron (2.4.9)
Maximum 20 ppm.
Dilute 5 mL of solution S to 10 mL with water R.
Magnesium and alkaline-earth metals (2.4.7)
Maximum 200 ppm, calculated as Ca.
10.0 g complies with the test for magnesium and alkaline-earth metals. The volume of 0.01 M sodium edetate used does not exceed 5.0 mL.
Loss on drying (2.2.32)
Maximum 3.0 per cent, determined on 1.000 g by drying in an oven at 105 °C for 3 h.
ASSAY
Dissolve 85.0 mg in water R, add 5 mL of dilute nitric acid R and dilute to 50 mL with water R. Titrate with 0.1 M silver nitrate, determining the end-point potentiometrically (2.2.20).
1 mL of 0.1 M silver nitrate is equivalent to 10.29 mg of NaBr.
Calculate the percentage content of NaBr using the following expression:
a − 2.902 b
a = percentage content of NaBr and NaCl obtained in the assay and calculated as NaBr;
b = percentage content of Cl obtained in the test for chlorides.
STORAGE
In an airtight container.
