Edition: BP 2025 (Ph. Eur. 11.6 update)
Action and use
Astringent.
Preparation
Erythromycin and Zinc Acetate Lotion Ph Eur
DEFINITION
Content
99.0 per cent to 101.0 per cent of C4H6O4Zn,2H2O.
CHARACTERS
Appearance
White or almost white crystalline powder or flakes.
Solubility
Freely soluble in water, soluble in ethanol (96 per cent).
IDENTIFICATION
A. It gives reaction (b) of acetates (2.3.1).
B. It gives the reaction of zinc (2.3.1).
TESTS
Solution S
Dissolve 10.0 g in carbon dioxide-free water R prepared from distilled 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).
pH (2.2.3)
5.8 to 7.0.
Dilute 10 mL of solution S to 20 mL with carbon dioxide-free water R.
Reducing substances
Boil for 5 min a mixture of 10 mL of solution S, 90 mL of water R, 5 mL of dilute sulfuric acid R and 1.5 mL of a 0.3 g/L solution of potassium permanganate R. The pink colour of the solution remains.
Chlorides (2.4.4)
Maximum 50 ppm.
Dilute 10 mL of solution S to 15 mL with water R.
Sulfates (2.4.13)
Maximum 100 ppm, determined on solution S.
Aluminium
Maximum 5 ppm.
Atomic absorption spectrometry (2.2.23, Method I).
Test solution Dissolve 2.50 g in 20 mL of a 200 g/L solution of cadmium- and lead-free nitric acid R and dilute to 25.0 mL with the same acid solution.
Reference solutions Prepare the reference solutions using aluminium standard solution (200 ppm Al) R, diluting with a 200 g/L solution of cadmium- and lead-free nitric acid R.
Source Aluminium hollow-cathode lamp.
Wavelength 309.3 nm.
Atomisation device Air-acetylene or acetylene-nitrous oxide flame.
Cadmium
Maximum 1 ppm.
Atomic absorption spectrometry (2.2.23, Method I).
Test solution Use the solution described in the test for aluminium.
Reference solutions Prepare the reference solutions using cadmium standard solution (0.1 per cent Cd) R, diluting with a 200 g/L solution of cadmium- and lead-free nitric acid R.
Source Cadmium hollow-cathode lamp.
Wavelength 228.8 nm.
Atomisation device Air-acetylene flame.
Iron
Maximum 50 ppm.
Atomic absorption spectrometry (2.2.23, Method I).
Test solution Dissolve 1.25 g in 20 mL of a 200 g/L solution of cadmium- and lead-free nitric acid R and dilute to 25.0 mL with the same acid solution.
Reference solutions Prepare the reference solutions using iron standard solution (20 ppm Fe) R, diluting with a 200 g/L solution of cadmium- and lead-free nitric acid R.
Source Iron hollow-cathode lamp.
Wavelength 248.3 nm.
Atomisation device Air-acetylene flame.
Lead
Maximum 1 ppm.
Atomic absorption spectrometry (2.2.23, Method I).
Test solution Dissolve 5.00 g in 20 mL of a 200 g/L solution of cadmium- and lead-free nitric acid R and dilute to 25.0 mL with the same acid solution.
Reference solutions Prepare the reference solutions using lead standard solution (0.1 per cent Pb) R, diluting with a 200 g/L solution of cadmium- and lead-free nitric acid R.
Source Lead hollow-cathode lamp.
Wavelength 283.3 nm.
Atomisation device Air-acetylene flame.
ASSAY
Dissolve 0.200 g in 5 mL of dilute acetic acid R. Carry out the complexometric titration of zinc (2.5.11). 1 mL of 0.1 M sodium edetate is equivalent to 21.95 mg of C4H6O4Zn,2H2O.
STORAGE
In a non-metallic container.
