Aluminum Monostearate
Aluminum,dihydroxy(octadecanoato-O-)-.
Dihydroxy(stearato)aluminum [7047-84-9].
»Aluminum Monostearate is a compound of aluminum with a mixture of solid organic acids obtained from fats,and consists chiefly of variable proportions of aluminum monostearate and aluminum monopalmitate.It contains the equivalent of not less than 14.5percent and not more than 16.5percent of Al2O3,calculated on the dried basis.
Packaging and storage—
Preserve in well-closed containers.
Identification—
A:
Heat 1g with a mixture of 25mLof water and 5mLof hydrochloric acid for 1hour,replacing the water as it evaporates:fatty acids are liberated,floating as an oily layer on the surface of the liquid,and the water layer responds to the tests for Aluminum á191ñ.
B:
Mix intimately 25g with 100mLof ether in a 500-mLflask,add 150mLof 3Nhydrochloric acid,attach a water-cooled condenser,and heat on a steam bath under reflux for 15minutes.Cool,and transfer both layers to a separator with the aid of an additional 100mLof ether.Shake vigorously,and allow the layers to separate.Remove the water layer,and wash the ether layer with three 30-mLportions of water.Transfer the ether layer to a small beaker,warm on a steam bath until the ether has evaporated and the fatty acids are clear,and dry the acids at 105
for 20minutes:the solidification temperature (see Fats and Fixed Oils á401ñ)of the fatty acids is not below 54.
for 20minutes:the solidification temperature (see Fats and Fixed Oils á401ñ)of the fatty acids is not below 54.
Loss on drying á731ñ—
Dry it at 80for 16hours:it loses not more than 2.0%of its weight.
for 16hours:it loses not more than 2.0%of its weight.
Arsenic,Method Iá211ñ—
Prepare the Test Preparationas follows.To 3.75g add 12.5mLof hydrochloric acid and 0.5mLof bromine TS,and heat on a steam bath until a transparent layer of melted fatty acid forms.Add 50mLof water,heat on a hot plate until the volume is about 25mL,and filter while hot.Cool,dilute the filtrate with water to 50mL,and to a 10-mLaliquot of this solution add 2.5mLof hydrochloric acid,then dilute with water to 55mL:the resulting solution meets the requirements of the test,the addition of 20mLof 7Nsulfuric acid specified for Procedurebeing omitted.The limit is 4ppm.
Heavy metals—
To 2g contained in a 250-mLflask add 20mLof water and 10mLof hydrochloric acid.Place a small funnel in the neck of the flask,and boil gently,replacing the water as it evaporates,until the fatty acids separate in a clear layer.Cool rapidly by rotating under a stream of cold water until the fatty acids solidify.Decant through a filter previously washed with 3Nhydrochloric acid,wash until the combined filtrate and washings measure 50mL,and mix.To 20mLof the pooled filtrate add 6Nammonium hydroxide,dropwise,until a permanent turbidity forms.Add 1Nacetic acid until the precipitate just dissolves,then add 2mLin excess,and add water to make 40mL.Add 1.2mLof thioacetamide-glycerin base TSand 2mLof pH3.5Acetate Buffer,and allow to stand for 5minutes:any brown color produced is not darker than that of a control solution prepared from 10mLof the pooled filtrate and 2mLof Standard Lead Solution(see Heavy Metals á231ñ)containing 10µg of lead per mL,then diluted with water to 20mLand treated in the same manner.The limit is 50µg per g.
Organic volatile impurities,Method IVá467ñ:
meets the requirements.
Assay—
Accurately weigh 5g of Aluminum Monostearate in a covered platinum crucible that previously has been ignited for 20minutes,cooled over anhydrous magnesium perchlorate,and weighed.Heat the open crucible gently,without allowing the specimen to burst into flame,and gradually increase the heat until the ash is white.Ignite the ash for 20minutes after the organic matter is removed,and cool.Add 15mLof water,cover the crucible with a small watch glass,and boil gently for 5minutes,using a small stirring rod to break up any large lumps of ash.Decant the solution through ashless filter paper,retaining most of the ash in the crucible.Repeat the extraction with water twice,passing the solutions through the same filter.Transfer the ash to the filter by means of a fine stream of water,and wash the crucible and the residue three times with warm water.Transfer the filter paper and the residue to the crucible,dry,and ignite for 20minutes after the filter paper has burned away.Following the ignition period,cover the crucible,cool over anhydrous magnesium perchlorate for 15minutes,and weigh the residue of Al2O3rapidly.Repeat the ignition until constant weight is attained,using 20-minute ignition periods and 15-minute cooling periods.From the weight of the residue remaining in the crucible,calculate the content of Al2O3.
Auxiliary Information—
Staff Liaison:Daniel K.Bempong,Ph.D.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 2954
Phone Number:1-301-816-8143