Method of Analysis for Sodium Benzoate : Pharmaceutical Guidelines

Method of Analysis for Sodium Benzoate

Procedure for analysis for Sodium Benzoate in quality control laboratory in pharmaceuticals.
1. Description
Dry, colourless crystals or almost white, crystalline powder; odourless; taste sweet.

2. Solubility
Very soluble in water; freely soluble in ethanol (70%), sparingly soluble in ethanol

3. Identification
A. Color Reaction:
Dissolve 150.0 g in sufficient carbon dioxide-free water prepared from distilled water to produce 300 ml (solution A). Dilute 1 ml of solution A to 100 ml with water. To 5 ml of the solution add 2 ml of freshly prepared 2M sodium hydroxide and 0.15 ml of freshly prepared copper sulphate solution; the solution is clear and blue and remains so on boiling. To the hot solution add 4 ml of 2M hydrochloric acid, heat to boiling and add 4 ml of 2M sodium hydroxide; an orange precipitate is produced immediately.
B. I.R:
The infrared absorption spectrum is concordant with the reference spectrum of Sucrose.
C. By TLC:
Stationary Phase: Silica gel as the coating substance
Test solution: Dissolve 10 mg of the substance to be examined in a mixture of 2 volumes of water and 3 volumes of methanol and dilute to 20 ml with the same mixture of solvents.
Reference solution (a): Dissolve 10 mg of sucrose WRS in a mixture of 2 volumes of water and 3 volumes of methanol and dilute to 20 ml with the same mixture of solvents.
Reference solution (b): Dissolve 10 mg each of fructose WRS, glucose WRS, lactose WRS and sucrose WRS in a mixture of 2 volumes of water and 3 volumes of methanol and dilute to 20ml with the same mixture of solvents.
Apply separately to the plate 2 µl of each solution and thoroughly dry the starting points. Develop over a path of 15 cm using a mixture of 10 volumes of water, 15 volumes of methanol, 25 volumes of anhydrous acetic acid and 50 volumes of ethylene chloride, measured accurately as a slight excess of water causes cloudiness of the solution. Dry the plate in a current of warm air. Repeat the development immediately, after renewing the mobile phase. Dry the plate in a current of warm air and spray evenly with a solution of 0.5 g of thymol in a mixture of 5 ml of sulphuric acid and 95 ml of alcohol. Heat at 130°C for 10 min. The principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with reference solution (a). The test is not valid unless the chromatogram obtained with reference solution (b) shows four clearly separated spots.

4. Acidity or Alkalinity
To 10 ml of solution A add 0.3 ml of phenolphthalein solution. The solution is colorless and not more than 0.6 ml of 0.01M sodium hydroxide is required to change the color of the solution to pink.

5. Appearance of the solution
Dissolve 50.0 g in carbon dioxide-free water R prepared from distilled water R and dilute to 100 ml with the same solvent. The solution is clear and colorless.

6. Conductivity
Limit: Not more than 35 µS.cm-1
Procedure
Dissolve 31.3 g in carbon dioxide-free water R prepared from distilled water R and dilute to 100.0 ml with the same solvent. Measure the conductivity of the solution (C1), while gently stirring with a magnetic stirrer, and that of the water used for preparing the solution (C2). The readings must be stable within 1 per cent over a period of 30 s. Calculate the conductivity of the solution of the substance to be examined from the expression:
= C1 – 0.35C2

7. Specific Optical Rotation
Limit: Between +65.9o and +67.0o
Weigh about 10.0g of the sample in a 100 ml volumetric flask. Dissolve in 50 ml of water. Shake continuously for 15 min and Dilute to 100 ml with water. Bring the solution to 25°C.
Blank: Take water as blank and bring the temperature to 25°C and fill Polarimeter tube. With Blank take five readings of the solution. Clean the Polarimeter tube and fill   with sample solution .Take five readings at 25°C.
Calculation:
Correction of rotation = Av. Observed reading - Av. Blank reading

                                                                       100  µ  x  100             
Specific optical rotation [µ]25°D  =  -----------------------------
                                                                      LC x  (100 - %LOD)
Where,      
µ = Corrected observed rotation
D = D-line of sodium light
L = Length of Polarimeter tube in dm
C = Concentration of the substance (in %)

8. Barium
To 10 ml of solution A add 1 ml of 1M sulphuric acids. When examined immediately and after 1 hour any opalescence is not more intense than that of a mixture of 1 ml of distilled water and 10 ml of solution A.

9. Calcium
To 1 ml of solution A add 9 ml of water and 1 ml of ammonium oxalate solution; the solution remains clear for at least 1 minute.

10. Heavy metals
Limit: Not more than 10 ppm
Standard solution: Into a 50-ml Nessler cylinder pipette 1.0 ml of lead standard solution (20 ppm Pb) and dilute with water to 25 ml. Adjust with dilute acetic acid or dilute ammonia solution to a pH between 3.0 and 4.0, dilute with water to about 35 ml and mix.
Test Solution: Add 0.1 ml of dilute hydrochloric acid to 8 ml of solution A and dilute with sufficient water to produce 25 ml. Adjust with dilute acetic acid or dilute ammonia solution to a pH between 3.0 and 4.0, dilute with water to about 35 ml and mix.
Procedure: To each of the cylinders containing the standard solution and test solution respectively add 10 ml of freshly prepared hydrogen sulphide solution, mix, dilute to 50 ml with water, allow standing for 5 minutes and view downwards over a white surface; the color produced with the test solution is not more intense than that produced with the standard solution.

11. Sulphite
To 4 ml of solution A add sufficient water to produce 20 ml, add 0.05 ml of 0.1M iodine and 0.05 ml of starch solution; a blue color develops.

12. Dextrin
To 2 ml of solution A add 8 ml of water, 0.05 ml of 2M hydrochloric acid and 0.05 ml of 0.05M iodine; the solution remains yellow or becomes faint bluish green.

13. Glucose and Invert Sugar
Dissolve 20 g in sufficient water to make 100 ml and filter if necessary. Place 50 ml of the clear solution in a 250-ml beaker, add 50 ml of alkaline cupric tartarate solution, cover the beaker with a watch glass, heat the mixture at such a rate that it comes to a boil in approximately 4 minutes and continue boiling for exactly 2 minutes. Add immediately 100 ml of recently boiled and cooled water and collect the precipitated cuprous oxide on a tared sintered -glass crucible. Wash the residue with the hot water, then with 10 ml of ethanol (95%) and finally with 10 ml of ether. Dry at 105 degree for 1 hour; the weight of the cuprous oxide is not more than 112 mg.

14. Coloring Matter
A) To 100 ml of solution A in a ground-glass-stoppered tube add 1 ml of dilute hypo phosphorous acid and allow to stand for 1 hour; no unpleasant odor is detectable.
B) Examine solution A under ultra-violet light (365 nm). Any fluorescence is not more intense than that of a solution containing 0.4 mg of quinine sulphate in 0.005M sulphuric acid.

15. Loss on Drying
Limit: Not more than 0.1%
Procedure
Weigh 1.000 g of substance in a clean and dried pre-weighed LOD Bottle. Cover the stopper and gently shake to distribute material to not more than 10 MM height. Place the LOD Bottle in oven and remove cover and leave it also inside the oven. Dry the sample at 105° C for 2 hr. On opening the chamber, immediately close the LOD Bottle, transfer it to desiccators and bring it to room temperature. Weigh up to constant weight.  
Calculation:
                                      W2 – W1
% Loss on Drying = --------------- X 100
                                      W2 – W3
Where: 
W1 = Weight of empty clean and dried LOD Bottle
W2 = Weight of LOD Bottle + sample
W3 = Weight of LOD Bottle + sample (After drying)

16. Lead
Limit: NMT 0.5 ppm
Procedure
Determined by atomic absorption spectrometry (2.2.23, Method II), using an apparatus equipped with a graphite furnace.
Test solution: Dissolve 50 mg in 0.5 ml of lead-free nitric acid R in a polyfluorocarbon-lined digestion bomb and heat at 150°C for 5 h. Allow to cool and dilute to 5.0 ml with water R.
Measure the absorbance at 283.3 nm, maintaining the drying temperature of the furnace at 110°C, the ashing temperature at 600°C and the atomizing temperature at 2100°C.

17. Sulphated ash
Limit: Not more than 0.1 %
Procedure:
Heat a silica crucible to redness for 10 min., allow cooling in desiccators and weighing. Place about 5g of accurately weighed substance in a 5ml of water then put it in the silica crucible, moisten with 2 ml sulphuric acid, ignite gently, again moisten with sulphuric acid and ignite at about 800o, cool, weigh again, ignite for 15 min. and repeat this procedure until two successive weighing do not differ by more than 0.5 mg.          
Calculation:
                                      W3– W1
% Sulphated Ash = ---------------- x 100
                                     W2 – W1
Where:   
W1 = Weight of empty platinum crucible
W2 = Weight of crucible + sample
W3 = Weight of crucible + residue (After ignition)





Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
[email protected] :liamENeed Help: Ask Question


Click Here

No comments: Read Comment Policy ▼

Post a Comment

CURRENT JOBS

Show All ❭❭Jobs by PharmaJobs

Write a Powerful CV

Click Here


Advertise Here

Get App for News Updates

Scan to Download

Android App
Android App

Recent Posts