Pharmaceutical Glaze
» Pharmaceutical Glaze is a specially denatured alcoholic solution of Shellac containing between 20.0 and 57.0 percent of anhydrous shellac and is made with either dehydrated alcohol or alcohol containing 5 percent of water by volume. The solvent is a specially denatured alcohol approved for glaze manufacturing by the Internal Revenue Service. It contains not less than 90.0 percent and not more than 110.0 percent of the labeled amount of shellac. It may contain waxes, and it may contain Titanium Dioxide as an opaquing agent.
Packaging and storage— Preserve in tight, lined metal or plastic containers, protected from excessive heat, preferably at a temperature below 25.
Labeling— Label it to indicate the shellac type (see under Shellac) and concentration, the composition of the solvent, and the quantity of titanium dioxide, if present. Where titanium dioxide or waxes are present, the label states that the Glaze requires mixing before use.
Acid value— Accurately weigh, by difference, a quantity of Glaze containing about 2 g of shellac, dissolve in 50 mL of alcohol that has been neutralized to phenolphthalein with 0.1 N sodium hydroxide, add additional phenolphthalein TS, if necessary, and titrate with 0.1 N sodium hydroxide VS to a pink endpoint. [note—For Glaze containing orange shellac, titrate slowly, stirring vigorously, until a glass rod dipped into the titrated solution produces a color change when touched to a drop of thymol blue TS on a spot plate. ] Express the acid value in terms of the number of mg of potassium hydroxide required per g of dried shellac. It meets the requirement for Acid value under Shellac.
Wax— Accurately weigh, by difference, a quantity of Glaze containing about 10 g of shellac into a 200-mL tall-form beaker. Add, with stirring, 150 mL of hot water containing 2.5 g of sodium carbonate, and proceed as directed in the test for Wax under Shellac, beginning with “immerse the beaker.” It meets the requirement for Wax under Shellac.
Identification, Heavy metals, and Rosin— Pour the remainder of the solution in the volumetric flask, retained from the Assay, onto a clean glass plate, and place the plate in a nearly vertical position. After drainage is complete, allow the resulting film to dry in a well-ventilated place at 20 for 1 hour, then place the plate in an oven at a temperature of 43 for 16 to 24 hours. Cool, and scrape the film from the plate with a sharp blade, discarding the thick edges: it responds to the Identification test and meets the requirements of the tests for Heavy metals, and Rosin under Shellac.
Assay— When testing Glaze that does not contain titanium dioxide, transfer an accurately weighed quantity of Glaze, containing about 17 g of shellac, to a 100-mL volumetric flask, add alcohol to volume, and mix. Pipet 3 mL into a tared dish containing about 10 g of washed sand and a small glass rod. [note—The tare weight includes the combined weights of the dish, the washed sand, and the glass rod. Retain the remaining solution in the volumetric flask for the tests for Identification, Heavy metals, and Rosin. ] Stir until a uniform mixture is obtained, allow the glass rod to remain in the dish, dry at 105 for 1 hour in an explosion-proof oven, cool, and weigh: the weight of shellac in the quantity of Glaze taken is obtained by subtracting the tare weight from the final weight of the dried dish and contents. When testing Glaze that contains titanium dioxide, transfer an accurately weighed quantity, containing about 10 g of solids, to a beaker, and add about 10 mL of alcohol. Filter off the pigment with the aid of vacuum. Wash the filter with alcohol, and transfer the combined filtrate and washing, with the aid of alcohol, to a 200-mL volumetric flask, add alcohol to volume, and mix. Pipet 6 mL into a tared dish containing about 10 g of washed sand and a small glass rod. Proceed as directed above, beginning with the Note.
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Topic/Question Contact Expert Committee
Monograph Hong Wang, Ph.D.
Senior Scientific Liaison
(EXC2010) Monographs - Excipients
USP35–NF30 Page 1809