Monographs: Pharmaceutical substances: Purified water (Aqua purificata)
Relative molecular mass. 18.02
Chemical name. Water; CAS Reg. No. 7732-18-5.
Description. A clear, colourless liquid; odourless.
Storage. Purified water should be kept in a well-closed container.
Labelling. The designation on the container should indicate the method of preparation.
Additional information. CAUTION:
Definition. Purified water contains no added substance.
Manufacture. Purified water is prepared by distillation, ion-exchange treatment, reverse osmosis, or other appropriate process from suitable water.
Heavy metals. Use 40 mL, adjust the pH with acetic acid (~60 g/l) PbTS and proceed as described under 2.2.3 Limit test for heavy metals, procedure 1; determine the heavy metals content according to Method A, allowing to stand for 10 minutes; the colour is not darker than that of 40 mL of the same untreated Purified water, the pH of which has been similarly adjusted.
Ammonia. Transfer 50 mL to a comparison tube, add 2 mL of alkaline potassio-mercuric iodide TS, and observe down the vertical axis of the tube in diffused light against a white background; the colour produced is not more intense than that of 50 mL of ammonia-free water R with the addition of 2 mL of dilute ammonium chloride TS.
Calcium and magnesium. To 100 mL add 2 mL of ammonium chloride buffer, pH 10.0, TS, 50 mg of mordant black 11 R, and 0.5 mL of disodium edetate (0.01 mol/l) VS; a pure blue colour is produced.
Carbon dioxide. To 25 mL add 25 mL of calcium hydroxide TS; it remains clear.
Chlorides. To 10 mL add 1 mL of silver nitrate (40 g/l) TS and allow to stand for 5 minutes; it remains clear and colourless.
Nitrates. Carefully superimpose 5 mL on 5 mL of diphenylamine/sulfuric acid TS, ensuring that the liquids do not mix; no blue colour appears at the interface of the two liquids.
Sulfates. To 10 mL add 1 mL of barium chloride (50 g/l) TS and allow to stand for 5 minutes; it remains clear and colourless.
Oxidizable matter. To 100 mL add 10 mL of sulfuric acid (~100 g/l) TS and 0.5 mL of potassium permanganate (10 g/l) TS and boil for 3 minutes; the colour is not completely destroyed.
Non-volatile residue. Evaporate 500 mL on a water-bath to dryness and dry the residue for 1 hour at 105 °C; not more than 5 mg (0.01 mg/mL).
Acidity or alkalinity. To 10 mL add 2 drops of methyl red/ethanol TS; a red colour does not appear. To a further 10 mL portion add 5 drops of bromothymol blue/ethanol TS; no blue colour develops.
Additional requirement for Purified water for sterile use
Complies with 3.2 Test for sterility.