Wheat Starch
» Wheat Starch is obtained from the caryopsis of Triticum aestivum L. (T. vulgare Vill.).
Packaging and storage— Preserve in well-closed containers. No storage requirements specified.
A: Under a microscope, using a mixture of glycerin and water (1:1) as a mounting agent, it presents large and small granules, and very rarely, intermediate sizes. The large granules, usually 10 µm to 60 µm in diameter, are discoid or, more rarely, reniform when seen face-on. The central hilum and striations are invisible or barely visible, and the granules sometimes show cracks on the edges. Seen in profile, the granules are elliptical and fusiform and the hilum appears as a slit along the main axis. The small granules, rounded or polyhedral, are 2 µm to 10 µm in diameter. Between crossed nicol prisms, the granules show a distinct black cross intersecting at the hilum.
B: Suspend 1 g of it in 50 mL of water, boil for 1 minute, and cool: a thin, cloudy mucilage is formed.
C: To 1 mL of the mucilage obtained in Identification test B, add 0.05 mL of iodine and potassium iodide TS 2: an orange-red to dark blue color is produced, which disappears on heating.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 The total aerobic microbial count does not exceed 1000 cfu per g, the total combined molds and yeasts count does not exceed 100 cfu per g, and it meets the requirements of the test for absence of Escherichia coli.
pH 791 Prepare a slurry by weighing 5.0 g of Wheat Starch, transferring to a suitable nonmetallic container, and adding 25.0 mL of freshly boiled and cooled water. Agitate continuously at a moderate rate for 1 minute. Stop the agitation, and allow to stand for 15 minutes. Determine the pH to the nearest 0.1 unit: the pH, determined potentiometrically, is between 4.5 and 7.0.
Loss on drying 731 Dry about 1 g, accurately weighed, at 130 for 90 minutes: it loses not more than 15.0% of its weight.
Residue on ignition 281: not more than 0.6%, determined on a 1.0-g test specimen.
Total protein: not more than 0.3% of total protein (corresponding to 0.048% N2, conversion factor: 6.25).
Procedure— Accurately weigh 6.0 g of test substance containing about 2 mg of nitrogen, transfer to a combustion flask, add 4 g of a powdered mixture consisting of 100 g of potassium sulfate, 5 g of cupric sulfate, and 2.5 g of selenium, and add three glass beads. Wash any adhering particles from the neck into the flask with 5 mL of sulfuric acid, allowing it to run down the sides of the flask, and mix the contents by rotation. Close the mouth of the flask loosely, for example by means of a glass bulb with a short stem, to avoid excessive loss of sulfuric acid. Heat gradually at first, then increase the temperature until there is vigorous boiling with condensation of sulfuric acid in the neck of the flask; precautions should be taken to prevent the upper part of the flask from becoming overheated. Continue the heating for 30 minutes, unless otherwise prescribed. Cool, dissolve the solid material by cautiously adding to the mixture 25 mL of water, cool again, and place in a steam distillation apparatus. Add 30 mL of sodium hydroxide solution (42 in 100), and distill immediately by passing steam through the mixture. Collect about 40 mL of distillate in 20.0 mL of 0.01 N hydrochloric acid and enough water to cover the tip of the condenser. Toward the end of the distillation, lower the receiver so that the tip of the condenser is above the surface of the acid. Take precautions to prevent any water on the outer surface of the condenser from reaching the contents of the receiver. Titrate the distillate with 0.01 N sodium hydroxide, using methyl purple TS as the indicator (n1 mL of 0.01 N sodium hydroxide).
Repeat the test using about 50 mg of glucose in place of the substance to be examined (n2 mL of 0.01 N sodium hydroxide).
Content of nitrogen = [0.01401 (n2 n1)] / m
where m is the amount of test substance weighed, in g.
Limit of iron— Shake 1.5 g of Wheat Starch with 15 mL of 2 N hydrochloric acid, and filter. Transfer 10 mL of the filtrate to a test tube, add 2 mL of citric acid solution (2 in 10) and 0.1 mL of thioglycolic acid, and mix. Add 10 N ammonium hydroxide until the solution is distinctly alkaline to litmus, dilute with water to 20 mL, and mix (Test solution). Prepare a Standard Iron Solution containing the equivalent of 10 µg of iron per mL as directed under Iron 241. Immediately before use, quantitatively dilute an accurately measured volume of this solution with water to obtain a Diluted Standard Iron Solution containing the equivalent of 1 µg of iron per mL. Prepare the Standard solution by transferring 10 mL of the Diluted Standard Iron Solution to a test tube and proceeding in the same manner as directed for the preparation of the Test solution, beginning with “add 2 mL of citric acid solution (2 in 10).” After 5 minutes, any pink color in the Test solution is not more intense than that in the Standard solution, corresponding to a limit of 10 µg of iron per g.
Limit of oxidizing substances— Transfer 4.0 g to a glass-stoppered, 125-mL conical flask, and add 50.0 mL of water. Insert the stopper, and swirl for 5 minutes. Transfer to a glass-stoppered, 50-mL centrifuge tube, and centrifuge to clarify. Transfer 30.0 mL of the clear supernatant to a glass-stoppered, 125-mL conical flask. Add 1 mL of glacial acetic acid and 0.5 to 1.0 g of potassium iodide. Insert the stopper, swirl, and allow to stand for 25 to 30 minutes in the dark. Add 1 mL of starch TS, and titrate with 0.002 N sodium thiosulfate VS to the disappearance of the starch–iodine color. Perform a blank determination, and make any necessary correction. Each mL of 0.002 N sodium thiosulfate is equivalent to 34 µg of oxidant, calculated as hydrogen peroxide. Not more than 1.4 mL of 0.002 N sodium thiosulfate is required (20 µg per g, calculated as H2O2).
Limit of sulfur dioxide: not more than 50 µg per g.
Carbon dioxide— Use carbon dioxide, with a flow regulator that will maintain a flow of 100 ± 10 mL per minute.
Bromophenol blue indicator solution— Dissolve 100 mg of bromophenol blue in 100 mL of dilute alcohol (1 in 5), and filter if necessary.
Hydrogen peroxide solution— Dilute 30 percent hydrogen peroxide with water to obtain a 3% solution. Just before use, add 3 drops of Bromophenol blue indicator solution, and neutralize to a violet-blue endpoint with 0.01 N sodium hydroxide. Do not exceed the endpoint.
apparatus— In this test, the sulfur dioxide is released from the test specimen in a boiling acid medium and is removed by a stream of carbon dioxide. The separated gas is collected in a dilute hydrogen peroxide solution where the sulfur dioxide is oxidized to sulfuric acid and titrated with standard alkali. The apparatus consists essentially of a 500-mL three-neck, round-bottom boiling flask; a separatory funnel having a capacity of 100 mL or greater; a gas inlet tube of sufficient length to permit introduction of the carbon dioxide within 2.5 cm of the bottom of the boiling flask; a reflux condenser having a jacket length of 200 mm; and a delivery tube connecting the upper end of the reflux condenser to the bottom of a receiving test tube. Apply a thin film of stopcock grease to the sealing surfaces of all the joints except the joint between the separatory funnel and the boiling flask, and clamp the joints to ensure tightness.
procedure— Add 150 mL of water to the boiling flask. Close the stopcock of the separatory funnel, and begin the flow of carbon dioxide at a rate of 100 ± 5 mL per minute through the Apparatus. Start the condenser coolant flow. Add 10 mL of Hydrogen peroxide solution to a receiving test tube. After 15 minutes, without interrupting the flow of carbon dioxide, remove the separatory funnel from the boiling flask, and transfer 25.0 g of test specimen into the boiling flask with the aid of 100 mL of water. Apply stopcock grease to the outer joint of the separatory funnel, and replace the separatory funnel in the boiling flask. Close the stopcock of the separatory funnel, and add 80 mL of 2 N hydrochloric acid to the separatory funnel. Open the stopcock of the separatory funnel to permit the hydrochloric acid solution to flow into the boiling flask, guarding against the escape of sulfur dioxide into the separatory funnel by closing the stopcock before the last few mL of hydrochloric acid drain out. Boil the mixture for 1 hour. Remove the receiving test tube, and transfer its contents to a 200-mL wide-necked, conical flask. Rinse the receiving test tube with a small portion of water, add the rinsing to the 200-mL conical flask, and mix. Heat on a water bath for 15 minutes, and allow to cool. Add 0.1 mL of Bromophenol blue indicator solution, and titrate the contents with 0.1 N sodium hydroxide VS until the color changes from yellow to violet-blue, with the color change lasting for at least 20 seconds. Perform a blank determination, and make any necessary correction (see Titrimetry 541). Calculate the content, in µg per g, of sulfur dioxide in the test specimen taken by the formula:
in which 32.03 is the milliequivalent weight of sulfur dioxide; V is the volume, in mL, of titrant consumed; N is the normality of the titrant; and W is the weight, in g, of test specimen taken.
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Topic/Question Contact Expert Committee
Monograph Kevin T. Moore, Ph.D.
(EM205) Excipient Monographs 2
61 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(MSA05) Microbiology and Sterility Assurance
62 Radhakrishna S Tirumalai, Ph.D.
Senior Scientist
(MSA05) Microbiology and Sterility Assurance
USP32–NF27 Page 1359
Pharmacopeial Forum: Volume No. 30(5) Page 1868