Anhydrous Citric Acid
(Ph Eur monograph 0455)
Anhydrous citric acid contains not less than 99.5 per cent and
not more than the equivalent of 101.0 per cent of 2-hydroxypropane-1,2,3-tricarboxylic
acid, calculated with reference to the anhydrous substance.
A white, crystalline powder, colourless crystals or granules,
very soluble in water, freely soluble in alcohol, sparingly soluble in ether. It melts at
about 153C with decomposition.
A, C, D, E.
1 g in 10 ml of water R. The solution
is strongly acidic (2.2.4).
by infrared absorption spectrophotometry (2.2.24), comparing with the spectrum obtained
with anhydrous citric acid CRS after drying both the substance being examined and
the reference substance at 100C to 105C for 24 h.
about 5 mg to a mixture of 1 ml of acetic anhydride R and 3 ml of pyridine R.
A red colour develops.
0.5 g in 5 ml of water R, neutralise
using 1M sodium hydroxide (about 7 ml), add 10 ml of calcium chloride solution R and
heat to boiling. A white precipitate is formed.
complies with the test for water (see Tests).
Appearance of solution
Dissolve 2.0 g in water
R and dilute to 10 ml with the same solvent. The solution is clear (2.2.1) and not more intensely coloured than
reference solution Y7, BY7 or GY7 (2.2.2, Method II).
Readily carbonisable substances
To 1.0 g in a cleaned test tube add 10 ml of sulphuric acid
R and immediately heat the mixture in a water-bath at 90C 1C for 60 min.
Immediately cool rapidly. The solution is not more intensely coloured than a mixture of 1
ml of red primary solution and 9 ml of yellow primary solution (2.2.2, Method I).
Dissolve 0.80 g in 4 ml of water R. Add 3 ml of hydrochloric acid R and
1 g of zinc R in granules. Boil for 1 min. Allow to stand for 2 min. Transfer the
supernatant liquid to a test-tube containing 0.25 ml of a 10 g/l solution of phenylhydrazine
hydrochloride R and heat to boiling. Cool rapidly, transfer to a graduated cylinder
and add an equal volume of hydrochloric acid R and 0.25 ml of a 50 g/l solution of potassium
ferricyanide R. Shake and allow to stand for 30 min. Any pink colour in the solution
is not more intense than that in a standard prepared at the same time in the same manner
using 4 ml of a 0.1 g/l solution of oxalic acid R (350 ppm, calculated as anhydrous
If intended for use in the manufacture of dialysis solutions,
it complies with the test for aluminium. Dissolve 20 g in 100 ml of water R and add 10 ml of acetate buffer solution
pH 6.0 R. The solution complies with the limit test for aluminium (0.2 ppm). Use as
the reference solution a mixture of 2 ml of aluminium standard solution (2 ppm Al) R,
10 ml of acetate buffer solution pH 6.0 R and 98 ml of water R. To prepare the blank use a mixture of 10 ml
of acetate buffer solution pH 6.0 R and 100 ml of water R.
Dissolve 1.0 g in distilled water R and dilute to 15 ml with the same solvent.
The solution complies with the limit test for sulphates (150 ppm).
Heavy metals (2.4.8)
Dissolve 5.0 g in several portions in 39 ml of dilute
sodium hydroxide solution R and dilute to 50 ml with distilled water R. 12 ml complies with limit test A for heavy
metals (10 ppm). Prepare the standard using lead standard solution (1 ppm Pb) R.
Not more than 1.0 per cent, determined on 2.000 g by the
semi-micro determination of water.
Sulphated ash (2.4.14)
Not more than 0.1 per cent, determined on 1.0 g.
Bacterial endotoxins (2.6.14)
Less than 0.5 IU/mg, if intended for use in the manufacture of
parenteral dosage forms without a further appropriate procedure for the removal of
Dissolve 0.550 g in 50 ml of water R. Titrate with 1M sodium
hydroxide, using 0.5 ml of phenolphthalein solution R as
1 ml of 1M sodium
hydroxide is equivalent to 64.03 mg of C6H8O7.
The label states:
where applicable, that the substance is free from bacterial
where applicable, that the substance is intended for use in
the manufacture of dialysis solutions.