.
1. Description
White
crystalline powder, odorless or almost odorless, hygroscopic.
2. Solubility
Freely soluble
in water and in ethanol (50%), sparingly soluble in ethanol (95%), practically
insoluble in fixed oils and in methylene chloride.
3. Identification
A. Melting Point
Limit: Between 96°C and 99°C
B. The IR absorption spectrum of precipitate is concordant with the propyl
paraben reference spectrum or with the spectrum obtained from propyl paraben
WRS.
C. By Thin Layer Chromatography
The principal
spot in the chromatogram obtained with test solution (b) is similar in position
and size to the principal spot in the chromatogram obtained with reference
solution (c). (Refer the test for related substances)
D. Reaction of sodium salt
Reaction (A)
Reagent required
15 % w/v
solution of potassium carbonate
Potassium
antimonate solutionProcedure
Ignite the
precipitate obtained in “Identification test B”. Dissolve 0.1 g of ignited
substance in 2 ml of water. Add 2 ml of 15 % w/v solution of potassium carbonate
and heat to boiling. No precipitate is produced. Add 4 ml of a freshly prepared
potassium antimonate solution and heat to boiling. Allow cooling in ice and if
necessary scratch the inside of the test-tube with a glass-red a dense white
precipitate is formed.
Reaction (B)
Reagent required
1M Acetic Acid
Magnesium
Uranyl acetate solution
Procedure
Ignite the
precipitate obtained in “Identification test B”. Dissolve 0.1 g of ignited
substance in 2 ml of water. Acidity with 1M acetic acid. Add a large excess of
Magnesium Uranyl acetate solution mix. A yellow, crystalline precipitate is
formed.
E. Color Reaction: An orange to red color is developed
Reagent required
Sodium
carbonate solution
Aminopyrazolone
solution
Potassium
ferricyanide solution
Procedure
Weigh &
transfer about 10 mg of the sample in a test tube, add 1 ml of sodium carbonate
solution, boil for 30 seconds and cool. Add 5 ml of aminopyrazolone solution
and 1 ml of potassium ferricyanide solution and mix. An orange to red color is
developed.
4. pH
Limit: Between 9.5 and 10.5
Procedure
Dissolve 0.1 g
sample 100 ml of water and measure the pH of solution.
5. Appearance of
solution
Clarity of solution
Reagent required
10% w/v
solution of hexamine
Hydrazine
sulphate AR.
Methanol AR
Sample Solution: Weigh accurately about 10.0 g. of the sample and
transfer into a clean and dried 100 ml volumetric flask, dissolve in water and
make up to volume to 100 ml with water. (Solution S)
Reference suspension I: Weigh accurately about 1.0 g. of hydrazine
sulphate and transfer into a clean and dried 100 ml volumetric flask, dissolve
in water and make up to volume to 100 ml with water and allow standing for 4 to
6 hrs. Add 25 ml of this solution to 25 ml of 10% w/v solution of hexamine mix
well and allow standing for 24 hrs. Mix well. Dilute 15 ml of above solution to
1000 ml with water. Dilute 5.0 ml of this suspension (after shaking) to 100 ml
with water.
Procedure
Into separate
matched, flat-bottomed Nessler cylinders, 15 to 25 mm in internal diameter and
of colourless, transparent, neutral glass, place sufficient quantity of the
sample solution, reference suspension and water, such that the Nessler
cylinders are filled to a depth of 40 mm. After five minutes, compare the
contents against a black background by viewing in diffused daylight down the
vertical axes of the cylinders. The sample solution is more clear or same as
compared to the diluent (water) or is less opalescent than reference
suspension.
6. Color of solution
Reagent required
Yellow Primary
Solution
Red Primary Solution
Blue Primary Solution
Blue Primary Solution
1 % w/v
Hydrochloric acid
Reference solution BY6: In a clean and dried 100 ml volumetric flask,
transfer 24 ml of yellow primary solution, 10 ml of red primary solution and 4
ml of blue primary solution. Make up the
volume to 100 ml with 1% w/v of hydrochloric acid. Dilute 5.0 ml of above
solution to 100 ml with 1.0% w/v HCl.
Sample solution: Use solution S
Procedure
Using identical
tubes of colorless, transparent, neutral glass with a flat base and an internal
diameter of 15 to 25 mm compare a 40-mm layer of the liquid being examined with
a 40-mm layer of water or of the reference solution BY6. Examine the columns of
the liquid in diffused daylight by viewing down the vertical axes of the tubes
against a white background. The appearance of sample solution is same as that
of water or the color intensity of sample solution is not greater than that of
reference solution BY6.
7. Chloride
Limit: Not more than 330 ppm
Nitric acid AR
0.1M silver
nitrate
Chloride
standard solution (25 ppm Cl)
Standard solution: Transfer 10 ml of chloride standard solution (25 ppm
Cl) into a clean and dried Nessler cylinder, add 5 ml of water.
Sample solution: Dissolve 1.0 g of sample in 20 ml of water; add 0.2
ml of nitric acid and filter. Transfer 15 ml of the filtrate into a clean and
dried Nessler cylinder.
Procedure
Add 10 ml of
nitric acid to both cylinders and add sufficient water to make volume to 50 ml.
Add 1 ml of 0.1 M silver nitrate, mix and allow standing for 5 minutes
protected from direct sunlight. Compare the opalescence if any, produced in the
sample solution with that produced with standard solution. The sample solution
is less opalescent as compare to the standard solution when viewed transversely
against a black background.
8. Sulphate
Limit: Not more than 300 ppm
Reagent required
25 % w/v
solution of barium chloride
Sulphate
standard solution ( 10 ppm SO4)
5M acetic acid
2M hydrochloric
acid
Standard preparation: 15 ml of Sulphate standard solution (10 ppm
SO4).
Sample preparation: Pipette out 25 ml of solution S into a clean, dried
50 ml volumetric flask, add 5 ml of water and 10 ml of hydrochloric acid,
dilute to 50 ml with water and filter. Dilute 10 ml of the filtrate to 15 ml
with water.
Procedure
Into two
separate Nessler cylinders take 1.5 of Sulphate Standard solution (10 ppm SO4),
add 1 ml of 25 % w/v solution of barium chloride. Mix allow to stand for 1
minute. Add 15 ml of sample preparation and 15 ml of standard preparation. Add
0.5 ml of 5M acetic acid. Allow to stand for 5 minutes. Compare the opalescence
if any, produced in the sample preparation with that produced with standard
solution. The opalescence produced with the sample preparation is not more
intense than that with standard solution
9. Related substance
By Thin Layer Chromatography
Stationary phase: silica gel 60 F254
Mobile Phase preparation: Mix 1 volume of glacial acetic acid, 30
volumes of water and 70 volumes of methanol.
Test solution (a): Weigh accurately about 100 mg of the sample and
transfer it into a 125 ml separating funnel. Add 10 ml of water and then add 2
ml of hydrochloric acid. Extract with 50 ml of ether. Collect the ether extract
and evaporate to dryness. Dissolve the residue in 10 ml of acetone.
Test solution (b): Dilute 1 ml of test solution (a) to 10 ml with
acetone.
Reference solution (a): Weigh accurately 34.3 mg of 4-hydroxybenzoic
acid and transfer it into a 100-ml volumetric flask. Dissolve it in acetone and
make up the volume to 100 ml with acetone.
Reference solution (b): Dilute 0.5 ml of the test solution (a) to 100
ml with acetone.
Reference solution (c): Weigh accurately 10 mg of propyl
parahydroxybenzoate WRS and transfer it into a 10 ml volumetric flask. Dissolve
in acetone and make up the volume to 10 ml with acetone.
Reference solution (d): Weigh accurately 10 mg of ethyl
parahydroxybenzoate WRS and transfer it into a 10 ml volumetric flask. Dissolve
in 1 ml of test solution (a) and dilute to 10 ml with acetone.
Procedure
Apply
separately to the plate 5ml of each solution. Keep the plate into the TLC chamber, previously
saturated with the mobile phase and allows the mobile phase to run over the
path of 15 cm. Remove the plate from the TLC chamber and allow it to dry in
air. Examine in the ultraviolet light at 254 nm. In the chromatogram obtained
with the test solution (a): any spot due to 4-hydroxybenzoic acid is not more
intense than the spot in the chromatogram obtained with the reference solution
(a) (4%); and any spot, apart from the principal spot and the spot due to
4-hydroxybenzoic acid, is not more intense than the spot in the chromatogram
obtained with the reference solution (b) (0.5%). The test is not valid unless
the chromatogram obtained with the reference solution (d) shows two clearly
separated spots.
10. Heavy metals
Limit: Not more than 10 ppm
Reagent required
Strong ammonia
Thioacetamide
reagent
Acetate buffer
pH 3.5
Lead standard
solution (10 ppm Pb)
25% w/v
Magnesium sulfate in 1M sulphuric acid
2M Hydrochloric
acid
Phenolphthalein
solution
Sample preparation: Weigh accurately and transfer 2.0 g. of the sample
in a silica crucible with 4 ml of a 25% w/v solution of magnesium sulfate in 1
M sulphuric acid. Mix using a glass rod
and heat cautiously to dryness on a water bath. Keep the crucible in muffle
furnace. Progressively heat to ignition, below 800°C and continue heating until
a white or at most grayish residue is produced. Allow to cool, moisten the
residue with 0.2 ml of 1M sulfuric acid, evaporate, ignite again and allow
cooling. The total period of ignition should not exceed 2 hours. Dissolve the residue using two 5-ml
quantities of 2M hydrochloric acid. Add 0.1 ml of phenolphthalein solution and
add strong ammonia drop wise until a pink color is produced. Cool, add glacial acetic acid until the
solution is decolorized and add a further 0.5 ml. Filter, if necessary and dilute the solution
to 20 ml with water.
Standard solution: Take 2 ml of lead standard solution (10 ppm lead)
in a silica crucible, add 4 ml of 25% w/v solution of magnesium sulphate in 1 M
sulphuric acid and repeat the procedure beginning at the words “Mix using a
glass rod………” under sample preparation.
Procedure
Take two clean
and dried Nessler cylinders for sample and standard solution. In sample
cylinder pipette out 12 ml of sample solution and in standard cylinder pipette
out 2 ml of sample solution and 10 ml of standard solution. Add to the both cylinders,
2 ml of acetate buffer pH 3.5, mix and add 1.2 ml of thioacetamide reagent,
mix, allow standing for 2 minutes. Any brown color produced in the sample
solution is not more intense than that produced in the standard solution.
11. Water
Limit: Not more than 5.0%
Reagent required
Anhydrous
methanol AR
KF reagent
Pyridine free single solution
Procedure
Take about 40
ml of anhydrous methanol in the titration vessel, neutralize with KF reagent
and find out the factor of KF reagent in mg H2O/ 5 ml in triplicate and enter
mean value.
Add accurately
about 500 mg of the sample to the titration vessel. Allow to titrate with KF
reagent to the electrometric end point. Record the percentage of water content
obtained by Karl Fischer titrator. Find out water content of sample in
triplicate and take mean value.
12. Assay
Limit: Not less than 99.0% and Not more than 102.0% of C10H11NaO3,
calculated with reference to the anhydrous substance.
Reagent required
Glacial acetic
acid
0.1M Perchloric
acid
Procedure
Weigh
accurately about 150 mg. of the sample in a clean, dried titration beaker, add
50 ml of glacial acetic acid and dissolve. Connect the beaker to the
Autotitrator and determine the end-point potentiometrically. Perform a blank
titration without the sample. 1 ml of 0.1M Perchloric acid is equivalent to
20.22 mg. of C10H11NaO3.
Calculation:
Net Volume =
sample burette reading – blank reading
V
x F x M x 100 x 100 100
% Assay on
anhydrous basis = ----------------------------- x --------------------
0.1 x W (100 - % water)
Where,
V = Consumed
volume of 0. 1M Perchloric acid
M = Molarity of
0. 1M Perchloric acid
F = Factor
W = Weight of
sample
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