» Agar is the dried, hydrophilic, colloidal substance extracted from Gelidium cartilagineum (Linné) Gaillon (Fam. Gelidiaceae), Gracilaria confervoides (Linné) Greville (Fam. Sphaerococcaceae), and related red algae (Class Rhodophyceae).
Botanic characteristics—
Agar— Usually in bundles consisting of thin, membranous, agglutinated strips or in cut, flaked, or granulated forms. May be weak yellowish orange, yellowish gray to pale yellow, or colorless. Is tough when damp, brittle when dry.
Histology— In water mounts Agar appears granular and somewhat filamentous; a few fragments of the spicules of sponges and a few frustules of diatoms may be present; in Japanese Agar, the frustules of Arachnoidiscus ehrenbergii Baillon often occur, being disk-shaped and from 100 µm to 300 µm in diameter.
Powdered Agar— White to yellowish white or pale yellow; in chloral hydrate TS its fragments are transparent, more or less granular, striated, and angular, and occasionally they contain frustules of diatoms.
A: Iodine TS colors some of the fragments of Agar bluish black, with some areas reddish to violet.
B: When boiled with 65 times its weight of water for 10 minutes, with constant stirring, and adjusted to a concentration of 1.5%, by weight, with hot water, Agar forms a clear liquid which congeals at 32 to 39 to form a firm resilient gel, which does not melt below 85.
Microbial enumeration tests 61 and Tests for specified microorganisms 62 It meets the requirements of the test for absence of Salmonella species.
Water, Method III 921 If necessary, cut it into pieces from 2 mm to 5 mm square, and dry at 105 for 5 hours: it loses not more than 20.0% of its weight.
Total ash 561: not more than 6.5%, on a dry-weight basis.
Acid-insoluble ash 561: not more than 0.5%, on a dry-weight basis.
Foreign organic matter 561: not more than 1.0%.
Limit of foreign insoluble matter— To 7.5 g add sufficient water to make 500 g, boil for 15 minutes, and readjust to the original 500 g. To 100 g of the uniformly mixed material add hot water to make 200 mL, heat almost to boiling, filter while hot through a tared filtering crucible, rinse the container with several portions of hot water, and pass these rinsings through the crucible. Dry the crucible and its contents at 105 to constant weight: not more than 15 mg (1.0%) remains.
Lead 251: 0.001%.
Limit of foreign starch— A solution made by boiling 0.10 g of it in 100 mL of water does not, upon cooling, produce a blue color upon the addition of iodine TS.
Gelatin— Dissolve about 1 g in 100 mL of boiling water, and allow to cool to about 50. To 5 mL of the solution add 2 to 3 drops of a mixture of 0.2 M potassium dichromate solution and 3 N hydrochloric acid (4:1): no yellow precipitate is formed.
Water absorption— Place 5.0 g in a 100-mL graduated cylinder, fill to the mark with water, mix, and allow to stand at 25 for 24 hours. Pour the contents of the cylinder through moistened glass wool, allowing the water to drain into a second 100-mL graduated cylinder: not more than 75 mL of water is obtained.
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Topic/Question Contact Expert Committee
Monograph Hong Wang, 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 1154
Pharmacopeial Forum: Volume No. 33(4) Page 702
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.