Galageenan
»Galageenan is the hydrocolloid obtained by extraction with water or aqueous alkali from the red seaweed class Rhodophyceaespecies Eucheuma gelatinae.Galageenan consists chiefly of potassium,sodium,calcium,magnesium,and ammonium sulfate esters of galactose and 3,6-anhydrogalactose copolymers.These hexoses are alternately linked in a-1,3and b-1,4in the polymer.The ester sulfate content ranges from 8percent to 18percent.In addition,it contains inorganic salts that originate from the seaweed and from the process of recovery from the extract.
Galageenan is recovered by alcohol precipitation or by freezing and pressing.
Packaging and storage—
Preserve in tight containers,preferably in a cool place.
Identification—
A:
Asolution (1in 50)prepared by heating a uniform dispersion in a hot water bath to 80
(Solution A)becomes more viscous upon cooling and may form a gel.
(Solution A)becomes more viscous upon cooling and may form a gel.
B:
Dilute a portion of Solution Awith about 4parts of water,and add 2to 3drops of methylene blue TS:a blue,stringy precipitate is formed.
Spectral range:
2000to 600cm-1.
Test solution—
Disperse 2g of it in 400mLof a solution containing 5g of edetate disodium in 1000mLof 60%isopropyl alcohol,and stir for 2hours.Filter with the aid of vacuum,and wash the residue with a total of 200mLof 65%isopropyl alcohol.Finish washing with a total of 100mLof 80%isopropyl alcohol.Dry the residue for 30minutes in a 60oven,and finally overnight in a 70vacuum oven.Break lumps by grinding with a mortar and pestle.Dissolve 15mg of the alcohol-treated material in 5mLof water.Heat for 10minutes in a water bath.Pipet 2mLonto a suitable nonsticking surface to produce a 5-µm thick film (when dry).
oven,and finally overnight in a 70vacuum oven.Break lumps by grinding with a mortar and pestle.Dissolve 15mg of the alcohol-treated material in 5mLof water.Heat for 10minutes in a water bath.Pipet 2mLonto a suitable nonsticking surface to produce a 5-µm thick film (when dry).
Procedure—
Subtract the baseline (drawn by connecting the minima in the range of 1500and 800cm-1)from the raw spectrum.Record the absorbances for the bands at 1220-1260,928-933,840-850,and 800-805cm-1relative to the absorbance at 1050cm-1:the absorbance values so obtained are within the ranges specified in the accompanying table.
| Wave Number cm-1 | Molecular Assignment |
Absorbance Relative to 1050cm-1 |
| Galageenan | ||
| 1220to 1260 | Ester sulfate | 0.3to 0.6 |
| 928to 933 | 3,6-anhydrogalactose | 0.3to 0.6 |
| 840to 850 | Galactose-4-sulfate | 0.1to 0.3 |
| 800to 805 | 3,6-anhydrogalac- tose-2-sulfate |
0.0to 0.1 |
Viscosity á911ñ—
Transfer 7.5g of Galageenan to a tared,tall-form,600-mLbeaker,add 450mLof water,and disperse with agitation for about 15minutes.Add water to bring the weight to 500g,and heat in a water bath,with continuous agitation,until a temperature of 80is reached.Add water to adjust for loss by evaporation,cool to between 76and 77,and place in a constant-temperature bath maintained at 75.Use a suitable rotational viscosimeter equipped with a spindle having a cylinder 1.88cm in diameter and 6.51cm in height,the immersion depth being 8.10cm (No.1spindle).Allow the spindle to rotate in the solution at 30rpm for 6revolutions,then observe the scale reading.Convert the scale reading to centipoises by multiplying by the constant for the spindle and speed employed.The viscosity at 75is not less than 15centipoises.
is reached.Add water to adjust for loss by evaporation,cool to between 76and 77,and place in a constant-temperature bath maintained at 75.Use a suitable rotational viscosimeter equipped with a spindle having a cylinder 1.88cm in diameter and 6.51cm in height,the immersion depth being 8.10cm (No.1spindle).Allow the spindle to rotate in the solution at 30rpm for 6revolutions,then observe the scale reading.Convert the scale reading to centipoises by multiplying by the constant for the spindle and speed employed.The viscosity at 75is not less than 15centipoises.
Microbial limits á61ñ—
The total aerobic microbial count does not exceed 200cfu per g,the total combined molds and yeasts count does not exceed 20cfu per g,and it meets the requirements of the tests for absence of Escherichia coliand Salmonellaspecies.
Loss on drying á731ñ—
Dry it at a pressure not exceeding 10mm of mercury at 70for 18hours,cool in a desiccator,and weigh:it loses not more than 12.5%of its weight.
for 18hours,cool in a desiccator,and weigh:it loses not more than 12.5%of its weight.
Acid-insoluble matter—
Transfer about 2g of Galageenan,accurately weighed,to a 250-mLbeaker containing 150mLof water and 1.5mLof sulfuric acid.Cover with a watch glass,and heat on a steam bath for 6hours,rubbing down the wall of the beaker frequently with a rubber-tipped stirring rod,and replacing any water lost by evaporation.Transfer about 500mg of a suitable filter aid,accurately weighed to the beaker,and pass through a tared filtering crucible equipped with a 2.4-cm glass fiber filter.Wash the residue several times with hot water,dry at 105for 3hours,cool in a desiccator,and weigh.The difference between the total weight and the sum of the weights of the filter aid,crucible,and glass fiber filter is the weight of the acid-insoluble matter.It is not more than 2.0%of the weight of Galageenan taken.
for 3hours,cool in a desiccator,and weigh.The difference between the total weight and the sum of the weights of the filter aid,crucible,and glass fiber filter is the weight of the acid-insoluble matter.It is not more than 2.0%of the weight of Galageenan taken.
Total ash á561ñ:
not more than 35.0%.
Lead á251ñ:
0.0005%.
Heavy metals,Method IIá231ñ:
0.002%.
Organic volatile impurities,Method IVá467ñ:
meets the requirements.
Content of sulfate—
Accurately weigh about 300mg of Galageenan onto an ashless filter paper.Fold the paper so as to enclose the sample,and place it into a 500-mL Kjeldahl flask.Add 45mLof nitric acid and bring to boil on a hot plate in a fume hood.Add nitric acid as necessary to keep the sample from evaporating to dryness.Continue boiling until digestion is complete and the volume of nitric acid remaining is about 10mL.Cool the mixture,and reduce the excess nitric acid by adding formaldehyde TSuntil the evolution of nitrogen oxide vapors has ceased.Heat this mixture on a hot plate to reduce the volume to about 10mL.Transfer the mixture to a 150-mLbeaker with the aid of several portions of water until the total volume is approximately 100mL.Add 0.5mLof hydrochloric acid,and bring to a boil on a hot plate.Add carefully 10mLof 0.25Mbarium chloride,and allow to boil for 1minute.Cover with a watch glass,and allow to stand overnight.Filter the solution through a tared,fine-porosity filtering crucible previously ignited in a muffle furnace at 550for 30minutes and cooled in a desiccator for 30minutes.Wash the barium sulfate precipitate so obtained on the crucible several times with boiling water,place the crucible in an oven,and heat at 100for 30minutes.Transfer the crucible to a muffle furnace,and ignite for 30minutes at 550.Remove the crucible,and cool in a desiccator for 30minutes.Weigh,and calculate the percentage of sulfate groups by the formula:
for 30minutes and cooled in a desiccator for 30minutes.Wash the barium sulfate precipitate so obtained on the crucible several times with boiling water,place the crucible in an oven,and heat at 100for 30minutes.Transfer the crucible to a muffle furnace,and ignite for 30minutes at 550.Remove the crucible,and cool in a desiccator for 30minutes.Weigh,and calculate the percentage of sulfate groups by the formula:
(96.02/233.43)(100WB/WS),
in which 233.43and 96.02are the molecular weights of barium sulfate and the sulfate group,respectively;WBis the weight,in mg,of barium sulfate obtained;and WSis the weight,in mg,of Galageenan taken.The percentage of sulfate is not less than 8%and not more than 18%.
Auxiliary Information—
Staff Liaison:Catherine Sheehan,B.Sc.,Scientist
Expert Committee:(EMC)Excipients:Monograph Content
USP28–NF23Page 3008
Phone Number:1-301-816-8262