myo-Inositol

(Ph. Eur. monograph 1805)

C₆H₁₂O₆    180.2    87-89-8

Vasodilator.

Ph Eur

Cyclohexane-1,2,3,5/4,6-hexol.

97.0 per cent to 102.0 per cent (anhydrous substance).

White or almost white, crystalline powder.

Very soluble in water, practically insoluble in ethanol (96 per cent).

A. Infrared absorption spectrophotometry (2.2.24).

Comparison  myo-inositol CRS.

B. Examine the chromatograms obtained in the assay.

Results  The principal peak in the chromatogram obtained with the test solution is similar in retention time and size to the principal peak in the chromatogram obtained with reference solution (a).

Dissolve 10.0 g in distilled water R and dilute to 100.0 mL with the same solvent.

Solution S is clear (2.2.1) and colourless (2.2.2, Method II).

Maximum 30 µS·cm^-1.

Dissolve 10.0 g in carbon dioxide-free water R prepared from distilled water R, with gentle warming if necessary, and dilute to 50.0 mL with the same solvent. Measure the conductivity of the solution while gently stirring with a magnetic stirrer.

Liquid chromatography (2.2.29).

Test solution  Dissolve 0.500 g of the substance to be examined in water R and dilute to 10.0 mL with the same solvent.

Reference solution (a)  Dissolve 0.500 g of myo-inositol CRS in water R and dilute to 10.0 mL with the same solvent.

Reference solution (b)  Dilute 2.0 mL of the test solution to 100.0 mL with water R. Dilute 5.0 mL of this solution to 100.0 mL with water R.

Reference solution (c)  Dissolve 0.5 g of myo-inositol R and 0.5 g of mannitol R in water R and dilute to 10 mL with the same solvent.

• — size: l = 0.3 m, Ø = 7.8 mm;

• — stationary phase: strong cation exchange resin (calcium form) R (9 µm);

• — temperature: 85 °C.

Mobile phase  water R.

Flow rate  0.5 mL/min.

Detection  Refractometer maintained at a constant temperature (at about 30-35 °C for example).

Injection  20 µL of the test solution and reference solutions (b) and (c).

Run time  Twice the retention time of myo-inositol.

Relative retention  With reference to myo-inositol (retention time = about 17.5 min): impurity A = about 1.3; impurity B = about 1.4.

System suitability  Reference solution (c):

• — resolution: minimum 4 between the peaks due to myo-inositol and impurity A.

• — impurities A, B: for each impurity, not more than 3 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.3 per cent);

• — unspecified impurities: for each impurity, not more than the area of the principal peak in the chromatogram obtained with reference solution (b) (0.10 per cent);

• — total: not more than 10 times the area of the principal peak in the chromatogram obtained with reference solution (b) (1.0 per cent);

• — disregard limit: 0.5 times the area of the principal peak in the chromatogram obtained with reference solution (b) (0.05 per cent).

To 10 mL of solution S add 1 mL of dilute sulfuric acid R. When examined immediately, and after 1 h, any opalescence in the solution is not more intense than that in a mixture of 1 mL of distilled water R and 10 mL of solution S.

Maximum 0.5 ppm.

Prepare the test solution by dissolving 20.0 g of the substance to be examined in 100 mL of water R, heating if necessary, and diluting to 200.0 mL with dilute acetic acid R.

Maximum 0.5 per cent, determined on 1.00 g.

Liquid chromatography (2.2.29) as described in the test for related substances with the following modification.

Injection  Test solution and reference solution (a).

Calculate the percentage content of C₆H₁₂O₆ from the declared content of myo-inositol CRS.

Specified impurities  A, B.

A. d-mannitol,

B. propane-1,2,3-triol (glycerol).

Ph Eur