Carmellose Calcium

(Ph Eur monograph 0886)

 

9050-04-8

 

Ph Eur


 

 

Definition

 

Carmellose calcium (carboxymethylcellulose calcium) is the calcium salt of a partly O-carboxymethylated cellulose. It may contain not more than 0.6 per cent of silica (SiO2).

 

Characters

 

A white or yellowish-white powder, hygroscopic after drying, practically insoluble in acetone, in alcohol and in toluene. It swells with water to form a suspension.

 

Identification

 

A.    Shake 0.1 g thoroughly with 10 ml of water  R. Add 2 ml of dilute sodium hydroxide solution R and allow to stand for 10 min (solution A). Dilute 1 ml of solution A to 5 ml with water  R. To 0.05 ml add 0.5 ml of a 0.5 g/l solution of chromotropic acid, sodium salt R in a 75 per cent m/m solution of sulphuric acid R and heat on a water-bath for 10 min. A reddish-violet colour develops.

 

B.    Shake 5 ml of solution A obtained in identification test A with 10 ml of acetone R. A white, flocculent precipitate is produced.

 

C.    Shake 5 ml of solution A obtained in identification test A with 1 ml of ferric chloride solution R1. A brown, flocculent precipitate is formed.

 

D.    Ignite 1 g and dissolve the residue in a mixture of 5 ml of acetic acid R and 10 ml of water  R. Filter if necessary and boil the filtrate for a few minutes. Cool and neutralise with dilute ammonia R1. The solution gives reaction (a) of calcium (2.3.1).

 

Tests

 

Solution S

 

Shake 1.0 g with 50 ml of distilled water  R, add 5 ml of dilute sodium hydroxide solution R and dilute to 100 ml with distilled water  R.

 

Alkalinity

 

Shake 1.0 g thoroughly with 50 ml of carbon dioxide-free water  R and add 0.05 ml of phenolphthalein solution R. No red colour develops.

 

Silica

 

Not more than 0.6 per cent. To the residue obtained in the test for sulphated ash add sufficient alcohol  R to moisten the residue completely. Add 6 ml of hydrofluoric acid R in small portions. Evaporate to dryness at 95-105C, taking care to avoid loss from sputtering. Cool and rinse the wall of the platinum crucible with 6 ml of hydrofluoric acid R. Add 0.5 ml of sulphuric acid R and evaporate to dryness. Progressively increase the temperature, ignite at 900C allow to cool in a desiccator and weigh. The difference between the mass of the residue obtained in the test for sulphated ash and the mass of the final residue is equal to the amount of silica in the substance to be examined.

 

Chlorides (2.4.4)

 

Heat 20 ml of solution S with 10 ml of dilute nitric acid R on a water-bath until a flocculent precipitate is produced. Cool, centrifuge and separate the supernatant liquid. Wash the precipitate with three quantities, each of 10 ml, of water  R, centrifuging each time. Combine the supernatant liquid and the washings and dilute to 100 ml with water  R. To 25 ml add 6 ml of dilute nitric acid R and dilute to 50 ml with water  R. 10 ml of the solution diluted to 15 ml with water  R complies with the limit test for chlorides (0.5 per cent).

 

Sulphates (2.4.13)

 

Heat 20 ml of solution S with 1 ml of hydrochloric acid R on a water-bath until a flocculent precipitate is produced. Cool, centrifuge and separate the supernatant liquid. Wash the precipitate with three quantities, each of 10 ml, of distilled water  R, centrifuging each time. Combine the supernatant liquid and the washings and dilute to 100 ml with distilled water  R. To 25 ml add 1 ml of dilute hydrochloric acid R and dilute to 50 ml with distilled water  R. 15 ml of the solution complies with the limit test for sulphates (1 per cent).

 

Heavy metals (2.4.8)

 

1.0 g complies with limit test D for heavy metals (20 ppm). Prepare the standard using 2 ml of lead standard solution (10 ppm Pb) R.

 

Loss on drying (2.2.32)

 

Not more than 10.0 per cent, determined on 1.000 g by drying in an oven at 100-105C for 4 h.

 

Sulphated ash (2.4.14)

 

10.0 per cent to 20.0 per cent, determined on 1.0 g in a platinum crucible and calculated with reference to the dried substance. Moisten with a mixture of equal volumes of water  R and sulphuric acid R.

 

 


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Action and use

 

Pharmaceutical aid.