Activated Charcoal
»Activated Charcoal is the residue from the destructive distillation of various organic materials,treated to increase its adsorptive power.
Packaging and storage— Preserve in well-closed containers.
Microbial limits á61ñ— It meets the requirements of the tests for absence of Salmonellaspecies and Escherichia coli.
Reaction— Boil 3.0g with 60mLof water for 5minutes,allow to cool,restore the original volume by the addition of water,and filter:the filtrate is colorless and is neutral to litmus.
Loss on drying á731ñ— Dry it at 120for 4hours:it loses not more than 15.0%of its weight.
Residue on ignition á281ñ: not more than 4.0%,a 0.50-g test specimen being used.
Acid-soluble substances— Boil 1.0g with a mixture of 20mLof water and 5mLof hydrochloric acid for 5minutes,filter into a tared porcelain crucible,and wash the residue with 10mLof hot water,adding the washing to the filtrate.To the combined filtrate and washing add 1mLof sulfuric acid,evaporate to dryness,and ignite to constant weight:the residue weighs not more than 35mg (3.5%).
Chloride á221ñ— A10-mLportion of the filtrate obtained in the test for Reactionshows no more chloride than is contained in 1.5mLof 0.020Nhydrochloric acid (0.2%).
Sulfate á221ñ— A10-mLportion of the filtrate obtained in the test for Reactionshows no more sulfate than is contained in 1.0mLof 0.020Nsulfuric acid (0.2%).
Sulfide— Place 0.50g in a small conical flask,add 20mLof water and 5mLof hydrochloric acid,and boil gently:the escaping vapors do not darken paper moistened with lead acetate TS.
Cyanogen compounds— Place a mixture of 5g of Activated Charcoal,50mLof water,and 2g of tartaric acid in a distilling flask connected to a condenser provided with a tightly fitting adapter,the end of which dips below the surface of a mixture of 2mLof 1Nsodium hydroxide and 10mLof water,contained in a small flask surrounded by ice.Heat the mixture in the distilling flask to boiling,and distill about 25mL.Dilute the distillate with water to 50mL,and mix.To 25mLof the diluted distillate add 12drops of ferrous sulfate TS,heat the mixture almost to boiling,cool,and add 1mLof hydrochloric acid:no blue color is produced.
Heavy metals á231ñ— Boil 1.0g with a mixture of 20mLof 3Nhydrochloric acid and 5mLof bromine TSfor 5minutes,filter,and wash the charcoal and the filter with 50mLof boiling water.Evaporate the filtrate and washing to dryness,and to the residue add 1mLof 1Nhydrochloric acid,20mLof water,and 5mLof sulfurous acid.Boil the solution until all of the sulfur dioxide is expelled,filter if necessary,and dilute with water to 50mL.To 20mLof the solution add water to make 25mL:the limit is 0.005%.
Uncarbonized constituents— Boil 0.25g with 10mLof 1Nsodium hydroxide for 5seconds,and filter:the filtrate is colorless.
Adsorptive power—
Alkaloids— Shake 1g of Activated Charcoal,previously dried at 120for 4hours,with a solution of 100mg of strychnine sulfate in 50mLof water for 5minutes,and filter through a dry filter,rejecting the first 10mLof the filtrate.To a 10-mLportion of the subsequent filtrate add 1drop of hydrochloric acid and 5drops of mercuric-potassium iodide TS:no turbidity is produced.
Dyes— Pipet 50mLof methylene blue solution (1in 1000)into each of two glass-stoppered,100-mLflasks.Add to one flask 250mg,accurately weighed,of Activated Charcoal,insert the stopper in the flask,and shake for 5minutes.Filter the contents of each flask through a dry filter,rejecting the first 20mLof each filtrate.Pipet 25-mLportions of the remaining filtrates into two 250-mLvolumetric flasks.Add to each flask 50mLof sodium acetate solution (1in 10),mix,and add from a buret 35.0mLof 0.1Niodine VS,swirling the mixture during the addition.Insert the stoppers in the flasks,and allow them to stand for 50minutes,shaking them vigorously at 10-minute intervals.Dilute each mixture with water to volume,mix,allow to stand for 10minutes,and filter through dry filters,rejecting the first 30mLof each filtrate.Titrate the excess iodine in a 100-mLaliquot of each subsequent filtrate with 0.1Nsodium thiosulfate VS,adding 3mLof starch TSas the endpoint is approached.Calculate the number of mLof 0.1Niodine consumed in each titration:the difference between the two volumes is not less than 0.7mL.
Auxiliary Information— Staff Liaison:Elena Gonikberg,Ph.D.,Scientist
Expert Committee:(PA4)Pharmaceutical Analysis 4
USP28–NF23Page 424
Phone Number:1-301-816-8251