Magnesium
stearate BP
Action
and use
Excipient
DEFINITION
Magnesium
stearate is a mixture of magnesium salts of different fatty acids consisting
mainly of stearic (octadecanoic) acid [(C17H35COO)2Mg] and palmitic (hexadecanoic)
acid [(C15H31COO)2 Mg] with minor proportions of other fatty acids. It contains
not less than 4.0 per cent and not more than 5.0 per cent of Mg, calculated with
reference to the dried substance. The fatty acid fraction contains not less than
40.0 per cent of stearic acid and the sum of stearic acid and palmitic acid is
not less than 90.0 per cent.
CHARACTERS
A white or
almost white, very fine, light powder, greasy to the touch, practically
insoluble in water and in ethanol.
IDENTIFICATION
First
identification C, D.
Second
identification A, B, D.
A. The
residue obtained in the preparation of solution S (see Tests) has a freezing
point not lower than 53C.
B. The acid
value of the fatty acids (2.5.1) is 195 to 210, determined on 0.200 g of
the residue obtained in the preparation of solution S dissolved in 25 ml of the
prescribed mixture of solvents.
C. Examine
the chromatograms obtained in the test for fatty acid composition. The retention
times of the principal peaks in the chromatogram obtained with the test solution
are approximately the same as those of the principal peaks in the chromatogram
obtained with the reference solution.
D. 1 ml of
solution S gives the reaction of magnesium.
TESTS
Solution S
To 5.0 g
Magnesium
stearate add 50 ml of peroxide-free ether, 20 ml of dilute nitric acid
and
20 ml of distilled water and heat under a reflux condenser until
dissolution is complete. Allow to cool. In a separating funnel, separate the
aqueous layer and shake the ether layer with 2 quantities, each of 4 ml, of distilled water. Combine the aqueous layers, wash with 15 ml of
peroxide-free
ether and dilute to 50 ml with distilled water R (solution S).
Evaporate the organic layer to dryness and dry the residue at 100-105°C. Keep
the residue for identification tests A and B.
Acidity
or alkalinity
To 1.0 g
Magnesium
stearate add 20 ml of carbon dioxide-free water R and boil for 1 min with
continuous stirring. Cool and filter. To 10 ml of the filtrate add 0.05 ml of bromothymol blue solution. Not more than 0.5 ml of
0.01 M hydrochloric
acid or 0.01 M sodium hydroxide is required to change the colour of
the indicator.
Chlorides
0.5 ml of
solution S diluted to 15 ml with water R complies with the limit test for
chlorides (0.1 per cent).
Sulphates
0.3 ml of
solution S diluted to 15 ml with distilled water complies with the limit
test for sulphates (0.5 per cent).
Cadmium
Not more
than 3.0 ppm of Cd, determined by atomic absorption spectrometry.
Lead
Not more
than 10.0 ppm of Pb, determined by atomic absorption spectrometry.
Nickel
Not more
than 5.0 ppm of Ni, determined by atomic absorption.
Loss on
drying
Not more
than 6.0 per cent, determined on 1.000 g by drying in an oven at 105C.
Microbial contamination
Total
viable aerobic count not more than 103 micro-organisms per gram,
determined by plate count. It complies with the test for Escherichia coli.
Magnesium Stearate USP-NF
Magnesium
Stearate
Octadecanoic acid, magnesium salt.
Magnesium
stearate [557-04-0].
Magnesium
Stearate is a compound of magnesium with a mixture of solid organic acids, and
consists chiefly of variable proportions of magnesium stearate and magnesium
palmitate. The fatty acids are derived from edible sources. It contains not less
than 4.0 percent and not more than 5.0 percent of Mg, calculated on the dried
basis.
Identification
A: Mix 5.0 g Magnesium
stearate with 50 mL of peroxide-free ether, 20 mL of diluted nitric acid, and 20
mL of water in a round-bottom flask. Connect the flask to a reflux
condenser, and reflux until dissolution is complete. Allow to cool, and
transfer the contents of the flask to a separator. Shake, allow the layers
to separate, and transfer the aqueous layer to a flask. Extract the ether
layer with two 4-mL portions of water, and add these aqueous extracts to the
main aqueous extract. Wash the aqueous extract with 15 mL of peroxide-free
ether, transfer the aqueous extract to a 50-mL volumetric flask, dilute with
water to volume, and mix. Retain this solution for the Limit of chloride and
Limit of sulfate tests. This solution responds to the test for Magnesium.
B: The retention times of the peaks corresponding to stearic acid and palmitic acid
in the chromatogram of the Test solution correspond to those in the
chromatogram of the System suitability solution, as obtained in the Relative content of stearic acid and palmitic acid test.
Microbial limits The total aerobic microbial count does not exceed 1000 cfu
per g, the total combined molds and yeasts count does not exceed 500 cfu per g,
and it meets the requirements of the tests for absence of Salmonella species and
Escherichia coli.
Acidity
or alkalinity Transfer 1.0 g
Magnesium
stearate to a 100-mL beaker, add 20 mL of carbon
dioxide-free water, boil on a steam bath for 1 minute with continuous shaking,
cool, and filter. Add 0.05 mL of bromothymol blue TS to 10 mL of the filtrate:
not more than 0.05 mL of 0.1 N hydrochloric acid or 0.1 N sodium hydroxide is
required to change the color of the indicator.
Loss on
drying Dry it at 105 to constant weight: it loses not more than 6.0% of its
weight.
Specific
surface area [NOTEIn cases where there are no functionality-related
concerns regarding the specific surface area of this article, this test may be
omitted.] Where the labeling states the specific surface area, determine the
specific surface area value as directed in the chapter in the P/P0 range of 0.05 to 0.15, and using out gassing conditions of 2 hours at 40 . If the
plot deviates from linearity for P/P0 values of 0.05 to 0.15, then a
suitable range of P/P0 values should be validated for linearity. In this
case, it is necessary to state the range of validated P/P0 values, the
increment of the P/P0 values, and the out gassing conditions employed.
Limit of
chloride A 10.0-mL portion of the aqueous solution obtained in Identification
test A shows no more chloride than corresponds to 1.4
mL of 0.020 N hydrochloric acid (0.1%).
Limit of
sulfate A 3.0 mL portion of the aqueous solution obtained in Identification
test A shows no more sulfate than corresponds to 3.0
mL of 0.020 N sulfuric acid (1.0%).
Lead Ignite 0.50 g Magnesium
stearate in a silica crucible in a muffle furnace at 475 to 500 for 15
to 20 minutes. Cool, add 3 drops of nitric acid, evaporate over a low flame to
dryness, and again ignite at 475 to 500 for 30 minutes. Dissolve the residue in
1 mL of a mixture of equal parts by volume of nitric acid and water, and wash
into a separator with several successive portions of water. Add 3 mL of Ammonium Citrate Solution
and 0.5 mL of Hydroxylamine Hydrochloride
Solution, and render alkaline to phenol red TS with ammonium hydroxide. Add
10 mL of Potassium Cyanide Solution. Immediately extract the solution
with successive 5-mL portions of Dithizone Extraction Solution, draining
off each extract into another separator, until the last portion of dithizone
solution retains its green color. Shake the combined extracts for 30 seconds
with 20 mL of 0.2 N nitric acid, and discard the chloroform layer. Add to the
acid solution 4.0 mL of Ammonia-Cyanide Solution and 2 drops of Hydroxylamine Hydrochloride Solution.
Add 10.0 mL of Standard Dithizone
Solution, and shake the mixture for 30 seconds. Pass the chloroform layer
through an acid-washed filter paper into a color-comparison tube, and compare
the color with that of a standard solution prepared as follows. To 20 mL of 0.2
N nitric acid add 5 ?g of lead, 4 mL of Ammonia-Cyanide Solution, and 2
drops of Hydroxylamine Hydrochloride Solution, and shake with 10.0 mL of Standard Dithizone Solution for 30 seconds. Pass through an acid-washed
filter paper into a color comparison tube. The color of the sample solution does
not exceed that of the control (0.001%).
Relative
content of stearic acid and palmitic acid The
stearate peak comprises not less than 40%; and the sum of the stearate and
palmitate peaks is not less than 90% of the total area of all fatty acid ester
peaks in the chromatogram.
Magnesium Stearate FCC
Magnesium
stearate FCC
Magnesium
stearate CAS:
[557-04-0]
DESCRIPTION
Magnesium
Stearate occurs as a fine, white, bulky powder that is unctuous and free from
grittiness. It is a compound of magnesium with a mixture of solid organic acids
obtained from edible sources and consists chiefly of variable proportions of
Magnesium Stearate and magnesium palmitate. It is insoluble in water, in
alcohol, and in ether.
Function: Ant caking agent; binder; emulsifier.
REQUIREMENTS
Identification:
A. Heat 1 g
of Magnesium
stearate with a mixture of 25 mL of water and 5 mL of hydrochloric acid.
Liberated fatty acids float as an oily layer on the surface of the liquid. The
water layer gives positive tests for Magnesium.
B. Mix 25 g
of Magnesium
stearate with 200 mL of hot water, then add 60 mL of 2 N sulfuric acid,
and while stirring frequently, heat the mixture until the fatty acids separate
cleanly as a transparent layer. Wash the fatty acids with boiling water until
they are free from sulfate, collect them in a small beaker, and warm them on a
steam bath until the water has separated and the fatty acids are clear. Allow
the acids to cool, pour off the water layer, then melt the acids, filter into a
dry beaker, and dry at 105° for 20 min. The solidification point of the fatty
acids so obtained is not below 54°
Assay: Not less than 6.8% and not more than 8.3% of MgO.
Lead: Not more than 5 mg/kg.
Loss on
Drying: Not more than 4.0%.
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