Thursday, 16 July 2009

Monographs: Pharmaceutical substances: Amyla - Starches

Chemical name. Starch; CAS Reg. No. 9005-25-8.

Description. A white to slightly yellowish, fine powder or ovoid granules whose size and shape are characteristic for each botanical variety; odourless.

Solubility. Practically insoluble in cold water and ethanol (~750 g/l) TS.

Category. Tablet and capsule binder; diluent; disintegrant.

Storage. Starches should be kept in tightly closed containers.

Labelling. The designation on the container of starches should state the botanical source.

Additional information. Types of starches should not be interchanged since the properties are characteristic for each one obtained from different botanical sources and thus their performance may not be identical. Attention should be paid to the microbiological purity since starches are of natural origin.


Definition. Starches consist of polysaccharide granules obtained from the grains of corn (Zea mays L.), of rice (Oryza sativa L.), of wheat (Triticum aestivum L.), or from the tubers of the potato (Solanum tuberosum L.).

Identity tests

A. To 1 g add 50 ml of water, heat to boiling for 1 minute, and cool; a thin cloudy mucilage is obtained from all starches other than potato starch, which gives a thicker and more translucent mucilage. (Keep the mucilages for test B.)

B. To 1 ml of the mucilage obtained in test A add 0.05 ml of iodine (0.005 mol/l) VS and mix; a dark blue colour is obtained which disappears on heating and reappears on cooling.

Microscopic examination

Corn starch - Angular polyhedral or rounded granules, up to 35 μm in diameter; central hilum consisting of a distinct cavity or several rayed central clefts.

Rice starch - Polyhedral granules, size 2-10 μm, either isolated or aggregated in ovoid masses; central hilum poorly visible.

Wheat starch - Two distinct types of granule, either simple lenticular, 20-50 μm in diameter, or small spherical, 5-10 μm in diameter; hilum and striations poorly visible.

Potato starch - Simple irregular, ovoid, or spherical granules, up to 100 μm in size; hilum near the narrower end; striations well marked and concentric.

Iron. Shake 1.5 g with 15 ml of hydrochloric acid (~70 g/l) TS and filter. The filtrate complies with the 2.2.4 Limit test for iron; not more than 10 μg/g.

Sulfated ash

Corn starch - not more than 6 mg/g.

Rice starch - not more than 10 mg/g.

Wheat starch - not more than 6 mg/g.

Potato starch - not more than 6 mg/g.

Loss on drying. Dry to constant mass at 100 °C:

Corn starch - not more than 150 mg/g.

Rice starch - not more than 150 mg/g.

Wheat starch - not more than 150 mg/g.

Potato starch - not more than 200 mg/g.

Acidity. To 10 g add 100 ml of ethanol (~600 g/l) TS previously neutralized using phenolphthalein/ethanol TS, shake for 1 hour, filter, and titrate 50 ml of the filtrate with sodium hydroxide (0.1 mol/l) VS; not more than 2.0 ml is required to change the colour of the solution.

Foreign matter. Using a microscope, not more than traces of cell debris are present, and there are no granules of any origin other than that stated on the label.

Oxidizing matter. Shake 5 g with a mixture of 10 ml of water and 1.2 ml of acetic acid (~300 g/l) TS until a suspension of homogenous appearance is obtained. Add 0.5 ml of a freshly prepared saturated solution of potassium iodide R; no blue, brown, or red colour is observed.

Sulfur dioxide. Mix 20g with 200 ml of water until a suspension of homogenous appearance is obtained. Filter. To 100 ml of the clear filtrate add 3 ml of starch TS and titrate with iodine (0.005 mol/l) VS until a permanent blue colour is obtained; not more than 2.7 ml is required (0.08 mg/g)

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