OCTYL GALLATE
Prepared at the 46th JECFA (1996), published in FNP 52 Add 4 (1996)
superseding specifications prepared at the 41st JECFA (1993), published in
FNP 52 Add 2 (1993). Metals and arsenic specifications revised at the 61st
JECFA (2003). No ADI was allocated at the 46thJECFA (1996)
SYNONYMS INS No. 311
DEFINITION
Chemical names Octyl gallate, octyl ester of gallic acid, n-octyl ester of 3,4,5-
trihydroxybenzoic acid, octyl 3,4,5-trihydroxybenzoate
C.A.S. number 1034-01-01
Chemical formula C15H22O5
Structural formula
Formula weight 282.34
Assay Not less than 98.5% on the dried basis
DESCRIPTION White to creamy-white crystalline odourless solid
FUNCTIONAL USES Antioxidant
CHARACTERISTICS
IDENTIFICATION
Solubility (Vol. 4)
Insoluble in water, freely soluble in ethanol, ether and propane-1,2-diol
Melting range (Vol. 4)
99 - 102o
Gallic acid Dissolve about 0.5 g of the sample in 10 ml of sodium hydroxide TS and
boil for 30 min under nitrogen. Maintaining a stream of nitrogen, cool the
mixture and acidify to pH 2-3 with sulfuric acid TS.
Filter the precipitate through a sintered glass crucible, wash with a
minimum amount of water and then dry at 110ºfor 2 h. The melting point of
the gallic acid so obtained is about 240º, with decomposition.
TLC separation of gallate
esters
Use a thin-layer plate prepared with silica gel G. Prepare a sample solution
by dissolving 10 mg of sample in 10 ml ethanol. Prepare control solution A
by dissolving 10 mg of octyl gallate in 10 ml ethanol and control solution B
by dissolving 10 mg of propyl gallate and 10 mg of octyl gallate in 10 ml
ethanol.
Place 5 µl of each solution on the plate. Develop the chromatogram to
about 15 cm from the starting point using a developing solvent containing
20 volumes glacial acetic acid, 40 volumes petroleum ether and 40
volumes toluene.
Dry the plate in air. Spray the plate with an indicator solution, containing
20% w/v phosphomolybdic acid in ethanol until a yellow colouration
persists.
Examine in daylight. After a few min there is a progressive change to blue
colouration. After 5 to 10 min expose the plate to ammonia vapours until
the background is white.
Examine in daylight. The principal spot of the sample solution corresponds
with that for octyl gallate in the control solutions. Suitable resolution of
propyl and octyl gallate spots is determined from control solution B.
PURITY
Loss on drying (Vol. 4)
Not more than 0.5% (90º, 6 h)
Note: Ventilation during drying is advisable
Sulfated ash (Vol. 4)
Not more than 0.05%
Test 2 g of the sample (Method I)
Chlorinated organic
compounds
Not more than 100 mg/kg as chlorine
Dissolve 1 g of the sample in 10 ml of 0.1N sodium hydroxide. Acidify with
nitric acid TS and filter off the precipitate. Mix the precipitate with 2 g of
calcium carbonate, dry the mixture and then ignite. Take up the ignition
residue in 20 ml of dilute nitric acid TS and filter. Mix the solution with 0.5
ml of 0.1 N silver nitrate. The turbidity should not be more than that
obtained in 20 ml of dilute nitric acid TS containing 0.5 ml of 0.1N silver
nitrate and 0.3 ml of 0.01N hydrochloric acid.
Free acid Not more than 0.5% as gallic acid
To a mixture of 50 ml of carbon dioxide-free water and 50 ml of acetone,
add 5 drops of bromocresol green TS and titrate with 0.005N hydrochloric
acid to match a buffer (pH 5) TS containing the same amount of indicator.
Dissolve 0.4 g of the sample in 50 ml of acetone and add 50 ml of carbon
dioxide-free water, 5 drops of bromocresol green TS and the amount of
0.005N hydrochloric acid found in the preliminary test to bring the solvent to
pH 5. Titrate the solution back to pH 5 with 0.05N sodium hydroxide,
matching against the buffer (pH 5) TS. Each ml of 0.05N sodium hydroxide
is equivalent to 8.506 mg of gallic acid.
Lead (Vol. 4) Not more than 2 mg/kg
Determine using an atomic absorption technique appropriate to the
specified level. The selection of sample size and method of sample
preparation may be based on the principles of the method described in
Volume 4, “Instrumental Methods.”
METHOD OF
ASSAY
Weigh accurately about 0.2 g of the dried sample into a 400-ml beaker. Add
150 ml of water and heat to boiling. Then with constant and vigorous
stirring add 50 ml of bismuth nitrate TS (II). Continue stirring for a few min
more until precipitation is complete, then allow the solution to cool to room
temperature. Filter the yellow precipitate on a weighed sintered-glass
crucible, wash first with cold 0.05N nitric acid and then with ice-cold water,
until free from acid. Dry at 110o to constant weight. Calculate the octyl
gallate content by the formula:
OCTYL GALLATE
SYNONYMS
DEFINITION
Chemical names
C.A.S. number
Chemical formula
Structural formula
Formula weight
Assay
DESCRIPTION
FUNCTIONAL USES
CHARACTERISTICS
IDENTIFICATION
Gallic acid
TLC separation of gallate esters
PURITY
Chlorinated organic compounds
Free acid
Lead (Vol. 4)
METHOD OF
ASSAY