Packaging and storage— Preserve in well-closed containers.

Identification— Add 2g in small portions to 100mLof water,with vigorous agitation.Allow to stand for at least 12hours to ensure complete hydration.Place 2mLof the resulting mixture on a suitable glass slide,and allow to air-dry at room temperature to produce a uniform film.Place the slide in a vacuum desiccator over a free surface of ethylene glycol.Evacuate the desiccator,and close the stopcock so that the ethylene glycol saturates the desiccator chamber.Allow to stand for 12hours.Record the X-ray diffraction pattern (see X-ray Diffraction á941ñ),and calculate the dvalues:several peaks are observed;the characteristic peak corresponds to a dvalue between 10.3and 10.7Angstrom units.

Microbial limits á61ñ— It meets the requirements of the test for absence of Escherichia coli.

pHá791ñ— Disperse 1.0g in 10mLof carbon dioxide-free water,and mix:the pHof the mixed dispersion so obtained is between 7.0and 9.5.

Loss on drying á731ñ— Dry it at 105to constant weight:it loses between 5.0%and 17.0%of its weight.

Loss on ignition á733ñ— When ignited at 1000for 1hour,it loses between 17.0%and 27.0%of its weight.

Volatile matter— When ignited at 600for 1hour,it loses between 7.5%and 12.5%of its weight on the dried basis.

Powder fineness— Add 50g to 450mLof water containing 5g of sodium pyrophosphate,and stir for 10minutes.Pour the resulting dispersion slowly through a No.325standard sieve (see Particle Size Distribution Estimation by Analytical Sieving á786ñ),and carefully wash the residue until clean.Dry the residue at 105to constant weight:the dry weight of the residue so obtained is not more than 0.30%of the weight of the specimen taken.

Acid-soluble matter— Boil 2.0g with 100mLof 0.2Nhydrochloric acid for 5minutes,and cool.Add water to adjust the volume to 100mL,and filter.Evaporate 50mLof the filtrate so obtained to dryness,and ignite the residue at 600:not more than 0.15g is found (15%).

Carbonate— Mix 1.0g with 15mLof 0.5Nsulfuric acid:no effervescence occurs.

Arsenic and Lead— To 5.0g add 50mLof 1Nnitric acid,and boil for 30minutes,adding 1Nnitric acid at times to maintain the volume.Filter into a 100-mLvolumetric flask,wash the filter with water,and dilute the combined filtrate and washings with water to volume.

Adsorptive capacity— To 10mLof a 1in 10suspension of the specimen in water add 80mLof methylene blue solution (1in 1000),and shake.Add 10mLof barium chloride solution (1in 50),and shake.Allow to stand for 15minutes.Transfer 40mLof the supernatant to a 50-mLcentrifuge tube,and centrifuge.To 5mLof the clear supernatant add 495mLof water,and mix:the color of the solution so obtained is not deeper than that of a solution containing 1.5µg of methylene blue per mL.

Organic volatile impurities,Method IVá467ñ: meets the requirements.

Expert Committee:(PA4)Pharmaceutical Analysis 4

USP28–NF23Page 202

Phone Number:1-301-816-8251