E 468 CROSS-LINKED SODIUM CARBOXYMETHYLCELLULOSE

Commission Directive 2000/63/EC

Synonyms Cross-linked carboxymethyl cellulose

Cross-linked CMC

Cross-linked sodium CMC

Cross-linked cellulose gum

Definition Cross-linked sodium carboxymethyl cellulose is the sodium salt of thermally cross-linked partly O-carboxymethylated cellulose

Chemical name Sodium salt of the cross-linked carboxymethyl ether cellulose

Chemical formula The polymers containing substituted anhydroglucose units with the general formula:

C₆H₇O₂(OR₁) (OR₂)(OR₃)
where R₁, R₂ and R₃ may be any of the following:
- H
- CH₂COONa
- CH₂COOH

Description Slightly hygroscopic, white to off white, odourless powder

Identification

A. Shake 1 g with 100 ml of a solution containing 4 mg/kg methylene blue and allow to settle. The substance to be examined absorbs the methylene blue and settles as a blue, fibrous mass

B. Shake 1 g with 50 ml of water. Transfer 1 ml of the mixture to a test tube, add 1 ml water and 0,05 ml of freshly prepared 40 g/l solution of alpha-naphthol in methanol. Incline the test tube and add carefully 2 ml of sulphuric acid down the side so that it forms a lower layer. A reddish-violet colour develops at the interface

C. It gives the reaction of sodium

Purity

Loss on drying Not more than 6 % (105 ºC, 3h)

Water solubles Not more than 10 %

Degree of substitution Not less than 0,2 and not more than 1,5 carboxymethyl groups per anhydroglucose unit

pH of 1 % Not less than 5,0 and not more than 7,0

Sodium content Not more than 12,4 % on anhydrous basis

Arsenic Not more than 3 mg/kg

Lead Not more than 5 mg/kg

Cadmium Not more than 1 mg/kg

Mercury Not more than 1 mg/kg