Ferrous Sulphate Heptahydrate
(Ph. Eur. monograph 0083)
FeSO4,7H2O 278.0 7782-63-0
Action and use
Treatment of iron-deficiency anaemia.
Preparation
Paediatric Ferrous Sulfate Oral Solution
DEFINITION
Content
98.0 per cent to 105.0 per cent.
CHARACTERS
Appearance
Light green, crystalline powder or bluish-green crystals, efflorescent in air.
Solubility
Freely soluble in water, very soluble in boiling water, practically insoluble in ethanol (96 per cent).
Ferrous sulfate heptahydrate is oxidised in moist air, becoming brown.
IDENTIFICATION
A. It gives the reactions of sulfates (2.3.1).
B. It gives reaction (a) of iron (2.3.1).
C. It complies with the limits of the assay.
TESTS
Solution S
Dissolve 4.0 g in a 5 per cent V/V solution of lead-free nitric acid R and dilute to 100.0 mL with the same solution.
pH (2.2.3)
3.0 to 4.0.
Dissolve 1.0 g in carbon dioxide-free water R and dilute to 20 mL with the same solvent.
Chlorides (2.4.4)
Maximum 200 ppm.
Dilute 5 mL of solution S to 10 mL with water R and add 5 mL of dilute nitric acid R. Prepare the standard with a mixture of 2 mL of water R, 5 mL of dilute nitric acid R and 8 mL of chloride standard solution (5 ppm Cl) R. Use 0.15 mL of silver
nitrate solution R2 in this test.
Elemental impurities
Any method that fulfils the requirements of general chapter 2.4.20. Determination of elemental impurities may be used.
| Element | Maximum content (ppm) |
| Chromium | 50 |
| Cobalt | 25 |
| Copper | 50 |
| Nickel | 50 |
Ferric ions
Maximum 0.3 per cent.
In a ground-glass-stoppered flask, dissolve 5.00 g in a mixture of 10 mL of hydrochloric acid R and 100 mL of carbon dioxide-free water R. Add 3 g of potassium iodide R, close the flask and allow to stand in the dark for 5 min. Titrate the liberated iodine with 0.1 M sodium thiosulfate, using 0.5 mL of starch solution R, added towards the end of the titration, as indicator. Carry out a blank test in the same conditions. Not more than 2.7 mL of 0.1 M sodium thiosulfate is used, taking
into account the blank titration.
Manganese
Maximum 0.1 per cent.
Atomic absorption spectrometry (2.2.23, Method II).
Test solution: Dilute 1.0 mL of solution S to 20.0 mL with a 5 per cent V/V solution of lead-free nitric acid R.
Reference solutions: Prepare the reference solutions using manganese standard solution (1000 ppm Mn) R, diluting with a 5 per cent V/V solution of lead-free nitric acid R.
Source: Manganese hollow-cathode lamp using a transmission band preferably of 1 nm.
Wavelength: 279.5 nm.
Atomisation device: Air-acetylene flame.
Zinc
Maximum 50 ppm.
Atomic absorption spectrometry (2.2.23, Method II).
Test solution: Solution S.
Reference solutions: Prepare the reference solutions using zinc standard solution (100 ppm Zn) R, diluting with a 5 per cent V/V solution of lead-free nitric acid R.
Source Zinc hollow-cathode lamp using a transmission band preferably of 1 nm.
Wavelength: 213.9 nm.
Atomisation device: Air-acetylene flame.
ASSAY
Dissolve 2.5 g of sodium hydrogen carbonate R in a mixture of 150 mL of water R and 10 mL of sulfuric acid R. When the effervescence ceases add to the solution 0.500 g of the substance to be examined and dissolve with gentle swirling. Add
0.1 mL of ferroin R and titrate with 0.1 M ammonium and cerium nitrate until the red colour disappears.
1 mL of 0.1 M ammonium and cerium nitrate is equivalent to 27.80 mg of FeSO4,7H2O.
STORAGE
In an airtight container.
