Lecithin

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[8002-43-5].

NF27

» Lecithin is a complex mixture of acetone-insoluble phosphatides, which consist chiefly of phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, and phosphatidyl inositol, combined with various amounts of other substances such as triglycerides, fatty acids, and carbohydrates, as separated from the crude vegetable oil source. It contains not less than 50.0 percent of acetone-insoluble matter.

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Packaging and storage—

Preserve in well-closed, light-resistant containers. Store at the temperature indicated on the label. Protect from excess heat and moisture.

NF27

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Labeling— Label it to indicate the storage conditions.

NF27

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USP Reference standards

—
USP Choline Chloride RS.

NF27

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Identification—

A: Transfer 1 g of Lecithin to a Kjeldahl flask, add 5 g of potassium sulfate, 0.5 g of cupric sulfate, and 20 mL of sulfuric acid. Incline the flask to a 45 degree angle, heat gently until the effervescence almost ceases, and raise the temperature to boiling. After the contents become a blue, transparent solution, heat for 1 to 2 hours, cool, and add an equal volume of water. To 5 mL of this solution, add 10 mL of ammonium molybdate solution (1 in 5), and heat. A yellow precipitate is formed.

Paper Chromatography (see Chromatography

621

)—

Test solution— To 0.5 g of Lecithin, add 5 mL of hydrochloric acid solution (1 in 2), heat in a water bath for 2 hours, and filter.

Reference solution: a choline chloride solution (1 in 200) using USP Choline Chloride RS.

Application volume: 10 µL.

Developing solvent solution: a mixture of n-butanol, water, and acetic acid (4 : 2 : 1).

Spray reagent: Dragendorff's TS.

Procedure— Use a suitable cellulose filter paper for chromatography. Develop the chromatogram over a path of 25 cm, and dry the paper in a current of air. Spray the paper with Spray reagent to develop a red-orange color, and locate the spots on the paper by examination under daylight: the RF value of the principal spot obtained from the Test solution corresponds to that obtained from the Reference solution.

NF27

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Acid value

401

: If the substance under test is a plastic or semisolid, soften the Lecithin by warming it briefly at a temperature not exceeding 60

, and then mix. Transfer about 2 g, accurately weighed, to a 250-mL conical flask, and dissolve it in 50 mL of

petroleum ether.

NF27 To this solution add 50 mL of alcohol, previously neutralized to phenolphthalein with 0.1 N sodium hydroxide, and mix. Add phenolphthalein TS, and titrate with 0.1 N sodium hydroxide VS to a pink endpoint that persists for 5 seconds.

Calculate the number of mg of potassium hydroxide required to neutralize the free acids in 1.0 g of Lecithin by the formula:

56.11NV / W

in which 56.11 is the molecular mass of potassium hydroxide; N is the normality of sodium hydroxide solution; V is the volume, in mL, of sodium hydroxide solution consumed in the titration; and W is the weight, in g, of Lecitin taken:

NF27 not more than 36 mg of potassium hydroxide

NF27 required to neutralize the free acids.

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Peroxide value— Transfer about 5 g of Lecithin, accurately weighed, into a 250-mL Erlenmeyer flask with a ground-glass stopper, add 35 mL of a mixture of chloroform and acetic acid (2:1), and mix. Completely dissolve the test specimen while shaking gently. The solution becomes transparent. Completely replace the air in the flask with nitrogen. While purging with nitrogen, add 1 mL of potassium iodide solution (prepared by dissolving 16.5 g of potassium iodide in water to make 100 mL), then stop the flow of the nitrogen, and immediately place a stopper in the flask. Shake for 1 minute, and allow to stand in a dark place for 5 minutes. Add 75 mL of water, replace the stopper again, shake vigorously. Titrate with 0.01 N sodium thiosulfate VS, adding starch TS as the endpoint is approached, and continue the titration until the blue starch color has just disappeared. Perform a blank determination (see Titrimetry

541

), and make any necessary correction. Calculate the peroxide value, as milliequivalents of peroxide per 1000 g of Lecithin, by the formula:

1000SN / W

in which S is the net volume, in mL, of sodium thiosulfate solution required for titration; N is the exact normality of the sodium thiosulfate solution; and W is the weight, in g, of Lecithin taken: the peroxide value is not more than 10.

NF27

Water, Method I

921

: not more than 1.5%.

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Hexane-insoluble matter— If the substance under test is a plastic or semisolid, soften the Lecithin by warming it at a temperature not exceeding 60

, and then mix. Weigh 10.0 g into a 250-mL conical flask, add 100 mL of

hexanes,

NF27 and shake until solution is apparently complete or until no more of any residue seems to be dissolving. Pass through a coarse-porosity filtering funnel that previously has been heated at 105

for 1 hour, cooled, and weighed, wash the flask with two 25-mL portions of

hexanes,

NF27 and pour both washings through the funnel. Dry the funnel at 105

for 1 hour. [Caution—Hexane is flammable. ] Cool to room temperature, and determine the gain in weight: not more than 0.3% is found.

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Lead

251

not more than

NF27 0.001%.

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Heavy metals, Method II

231

not more than

NF27 20 µg per g.

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Content of acetone-insoluble matter— If the substance under test is a plastic or semisolid, soften the Lecithin by warming it briefly at a temperature not exceeding 60

, and then mix. Transfer about 2 g to a 40-mL centrifuge tube that previously has been tared

along

NF27 with a stirring rod, cool, and weigh accurately. Add 15.0 mL of acetone, warm carefully in a water bath to melt the test specimen without evaporating the acetone, but with stirring to aid complete

dissolution,

NF27 and place in an ice-water bath for 5 minutes. Add acetone that previously has been chilled to 0

to 5

to the 40-mL mark on the tube, stirring during the addition. Cool in an ice-water bath for 15 minutes, stir, remove the rod, clarify by centrifuging at about 2000 rpm for 5 minutes, and decant. Break up the residue with the stirring rod, and refill the centrifuge tube to the 40-mL mark with chilled acetone, while stirring. Cool in an ice-water bath for 15 minutes, stir, remove the rod, centrifuge, and decant. Break up the residue with the stirring rod. Place the tube in a horizontal position until most of the acetone has evaporated, mix again, and heat the tube containing the acetone-insoluble residue and the stirring rod at 105

to constant weight. [Caution—Acetone is flammable. ] Determine the weight of the residue, and calculate the percentage of acetone-insoluble matter.

Auxiliary Information— Please check for your question in the FAQs before contacting USP.

Topic/Question	Contact	Expert Committee
Monograph	Hong Wang, Ph.D. Scientist 1-301-816-8351	(EM205) Excipient Monographs 2
Reference Standards	Lili Wang, Technical Services Scientist 1-301-816-8129 RSTech@usp.org

USP32–NF27 Page 1266

Pharmacopeial Forum: Volume No. 33(6) Page 1249

Chromatographic Column—

LECITHIN

Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.