Betadex

Betacyclodextrin

 

(Ph Eur monograph 1070)

 

[C6H10O5]7              1135       68168-23-0 (monohydrate)

 

Ph Eur

 

 

Definition

 

Betadex (betacyclodextrin) contains not less than 98.0 per cent and not more than the equivalent of 101.0 per cent of cyclo-a-(1®4)-D-heptaglucopyranoside, calculated with reference to the dried substance.

 

Characters

 

A white or almost white, amorphous or crystalline powder, sparingly soluble in water, freely soluble in propylene glycol, practically insoluble in ethanol and in methylene chloride.

 

Identification

 

A.    It complies with the test for specific optical rotation (see Tests).

 

B.    Examine the chromatograms obtained in the assay. The retention time and size of the principal peak in the chromatogram obtained with test solution (b) are approximately the same as those of the principal peak in the chromatogram obtained with reference solution (c).

 

C.    Dissolve 0.2 g in 2 ml of iodine solution R4 by warming on a water-bath, and allow to stand at room temperature. A yellowish-brown precipitate is formed.

 

Tests

 

Solution S

 

Dissolve 1.000 g in carbon dioxide-free water  R with heating, allow to cool and dilute to 100.0 ml with the same solvent.

 

Appearance of solution

 

Solution S is clear  (2.2.1).

 

pH (2.2.3)

 

To 10 ml of solution S add 0.1 ml of a saturated solution of potassium chloride R. The pH of the solution is 5.0 to 8.0.

 

Specific optical rotation (2.2.7)

 

+160 to +164, determined on solution S and calculated with reference to the dried substance.

 

Reducing sugars

 

Test solution

 

To 1 ml of solution S add 1 ml of cupri-tartaric solution R4. Heat on a water-bath for 10 min, cool to room temperature. Add 10 ml of ammonium molybdate reagent R1 and allow to stand for 15 min.

 

Reference solution

 

Prepare a reference solution at the same time and in the same manner as the test solution, using 1 ml of a 0.02 g/l solution of glucose R.

 

Measure the absorbance of the test solution and the reference solution (2.2.25) at the maximum at 740 nm using water  R as the compensation liquid. The absorbance of the test solution is not greater than that of the reference solution (0.2 per cent).

 

Light-absorbing impurities

 

Examine solution S between 230 nm and 750 nm (2.2.25). Between 230 nm and 350 nm, the absorbance is not greater than 0.10. Between 350 nm and 750 nm, the absorbance is not greater than 0.05.

 

Related substances

 

Examine by liquid chromatography (2.2.29), as described under Assay. Inject separately test solution (a) and reference solution (b). In the chromatogram obtained with test solution (a): the areas of any peaks corresponding to gammacyclodextrin and alphacyclodextrin are not greater than half of the area of the corresponding peaks in the chromatogram obtained with reference solution (b) (0.25 per cent); the sum of the areas of all the peaks, apart from the principal peak and any peaks corresponding to alphacyclodextrin and gammacyclodextrin, is not greater than half of the area of the peak corresponding to betadex in the chromatogram obtained with reference solution (b) (0.5 per cent).

 

Residual solvents

 

Not more than 10 ppm of trichloroethylene and not more than 10 ppm of toluene. Examine by head-space gas chromatography (2.2.28), using the standard additions method and ethylene chloride R as the internal standard.

 

Test solutions

 

In each of four identical 20 ml flasks, dissolve 500 mg of the substance to be examined in water  R and add 0.10 g of calcium chloride R and 30 ml of a-amylase solution R. Add 1 ml of reference solutions (a), (b), (c) and (d), adding a different solution to each flask. Dilute to 10 ml with water  R.

 

Reference solutions

 

Prepare reference solution (a) containing 10 ml of ethylene chloride R per litre. From reference solution (a), prepare reference solutions (b), (c) and (d) containing per litre: 5 ml, 10 ml and 15 ml each of trichloroethylene R and of toluene R.

 

The chromatographic procedure may be carried out using:

 

a fused-silica column 25m long and 0.32 mm in internal diameter coated with a layer about 1 mm thick of macrogol 20 000 R,

 

helium for chromatography R as the carrier gas,

 

a flame-ionisation detector,

 

maintaining the temperature of the column at 50C, that of the injection port at 140C and that of the detector at 280C. Place the samples in a thermostated chamber at 45C for 2 h. Inject 200 ml of the head-space of each flask and repeat each test at least three times. The retention time of toluene is about 10 min. The test is not valid unless: the resolutions between the peaks corresponding to trichloroethylene and toluene and between the peaks corresponding to toluene and ethylene chloride are greater than 1.1 and the relative standard deviations of the ratios of the areas of the peaks corresponding to trichloroethylene and toluene to that of the peak corresponding to ethylene chloride are less than 5 per cent.

 

Calculate the content of trichloroethylene and of toluene taking their relative densities to be 1.46 and 0.87, respectively.

 

Heavy metals (2.4.8)

 

1.0 g complies with limit test C for heavy metals (10 ppm). Prepare the standard using 1 ml of lead standard solution (10 ppm Pb) R.

 

Loss on drying (2.2.32)

 

Not more than 16.0 per cent, determined on 1.000 g by drying in an oven at 120C for 2 h.

 

Sulphated ash (2.4.14)

 

Not more than 0.1 per cent, determined on 1.0 g.

 

Assay

 

Examine by liquid chromatography (2.2.29).

 

Test solution (a)

 

Dissolve 0.25 g of the substance to be examined in water  R with heating, cool and dilute to 25.0 ml with the same solvent.

 

Test solution (b)

 

Dilute 5.0 ml of test solution (a) to 50.0 ml with water  R.

 

Reference solution (a)

 

Dissolve 25.0 mg of alfadex CRS, 25.0 mg of gammacyclodextrin CRS and 50.0 mg of betadex CRS in water  R and dilute to 50.0 ml with the same solvent.

 

Reference solution (b)

 

Dilute 5.0 ml of reference solution (a) to 50.0 ml with water  R.

 

Reference solution (c)

 

Dissolve 25.0 mg of betadex CRS in water  R and dilute to 25.0 ml with the same solvent.

 

The chromatographic procedure may be carried out using:

 

a stainless steel column 0.25 m long and 4.6 mm in internal diameter packed with octadecylsilyl silica gel for chromatography R (10 mm),

 

as mobile phase at a flow rate of 1.5 ml/min a mixture of 10 volumes of methanol  R and 90 volumes of water  R,

 

as detector a differential refractometer,

 

a 50 ml loop injector.

 

Equilibrate the column with the mobile phase at a flow rate of 1.5 ml/min for about 3 h. Inject each solution. Record the chromatograms for 1.5 times the retention time of betadex. Adjust the sensitivity of the detector so that the height of the peak corresponding to gammacyclodextrin, in the chromatogram obtained with reference solution (a), is 55 per cent to 75 per cent of the full scale of the recorder. The retention time of betadex is about 10 min, the relative retention time of gammacyclodextrin is about 0.3 and that of alfadex is about 0.45. The test is not valid unless the resolution between the peaks corresponding to gammacyclodextrin and alfadex is not less than 1.5, and the relative standard deviation of the area of the peak corresponding to betadex is less than 2.0 per cent. If necessary, adjust the concentration of methanol in the mobile phase to achieve the required resolution. Calculate the percentage content of [C6H10O5]7 from the area of the principal peak in each of the chromatograms obtained with test solution (b) and reference solution (c) and the declared content of betadex CRS.

 

Storage

 

Store in an airtight container .

 

Impurities

 

A.    n = 6: alfadex,

 

B.    n = 8: gammacyclodextrin.

 

 

 


Ph Eur

 

Action and use

 

Pharmaceutical aid.