Guar Gum
» Guar Gum is a gum obtained from the ground endosperms of Cyamopsis tetragonolobus (Linné) Taub. (Fam. Leguminosae). It consists chiefly of a high molecular weight hydrocolloidal polysaccharide, composed of galactan and mannan units combined through glycosidic linkages, which may be described chemically as a galactomannan.
Packaging and storage— Preserve in well-closed containers.
A: Place about 2 g in a 400-mL beaker, moisten it with about 4 mL of isopropyl alcohol, add 200 mL of cold water with vigorous stirring, and continue stirring until the gum is completely and uniformly dispersed: an opalescent, viscous solution results.
B: Place about 100 mL of the solution prepared in Identification test A in a 400-mL beaker, heat in a boiling water bath for about 10 minutes, and cool: no appreciable increase in viscosity is produced (distinction from locust bean gum—see Reagents in the section Reagents, Indicators, and Solutions).
Loss on drying 731 Dry it at 105 for 5 hours: it loses not more than 15.0% of its weight.
Total ash 561: not more than 1.5% of ash.
Acid-insoluble matter— Transfer about 1.5 g of Guar Gum, accurately weighed, to a 250-mL beaker containing 150 mL of water and 1.5 mL of sulfuric acid. Cover the beaker with a watch glass, and heat the mixture on a steam bath for 6 hours, rubbing down the wall of the beaker frequently with a rubber-tipped stirring rod, and replacing any water lost by evaporation. At the end of the 6-hour heating period add about 500 mg of a suitable filter aid, accurately weighed, and filter through a suitable tared, ashless filter. Wash the residue several times with hot water, dry the filter and its contents at 105 for 3 hours, cool in a desiccator, and weigh: the amount of acid-insoluble matter, determined by subtracting the weight of filter aid from that of the residue, is not more than 7.0% of the Guar Gum taken.
Lead 251 Prepare a Test Preparation as directed in the chapter, and use 10 mL of Diluted Standard Lead Solution (10 µg of Pb) for the test: the limit is 0.001%.
Protein— Transfer about 1.0 g of Guar Gum, accurately weighed, to a 500-mL Kjeldahl flask, and proceed as directed for Method I under Nitrogen Determination 461: the amount of protein, obtained by multiplying by 6.25 the percentage of nitrogen determined, is not more than 10.0% of the Guar Gum taken.
Starch— To a 1 in 10 solution of Guar Gum add a few drops of iodine TS: no blue color is produced.
Content of galactomannans— Subtract from 100.0 the total percentages of Loss on drying, Total ash, Acid-insoluble matter, and Protein: the content of galactomannans is not less than 66.0%.
Auxiliary Information— Please check for your question in the FAQs before contacting USP.
Topic/Question Contact Expert Committee
Monograph Hong Wang, Ph.D.
(EM205) Excipient Monographs 2
USP32–NF27 Page 1248
Pharmacopeial Forum: Volume No. 29(6) Page 2017
Chromatographic Column—
Chromatographic columns text is not derived from, and not part of, USP 32 or NF 27.