1.0 Description: Visual

2.0 Average Weight: Check weight of 20 tablets at randomly and calculate the average weight by formula :

wt of 20 tablets (gm) x 1000 /20  found avg. wt in mg

3.0) Uniformity of weight:

Weigh 20 tablets selected at random and calculate the average weight. Not more than two of the individual weights deviate from the average weight by more than the percentage shown in table.

Tablets were weighed individually and the percentage of deviation of its weight from the average weight was determined for each tablet.

Formula for calculate the percentage of deviation = (experimental weight – theoretical weight)    x 100%

Theoretical weight

Average weight of tablets Percentage deviation
More than 80mg but Less than 250mg 7.5 %
250mg or More 5 %
  • Identification Test:
  1. When examined in the range 230nm to 360nm, the solution obtained in the assay shows an absorption maximum only at about 250nm.
  2. Shake a quantity of the powdered tablets containing 0.1 gm of allopurinol with 5ml of dilute sodium hydroxide solution, add 3ml of lithium and sodium molybdo-phosphotungstate solution and 5ml of a 20 per cent w/v solution of sodium carbonate; a grey- blue colour is produced.

5.0)      Hardness:

The standard method used for tablet hardness testing is compression testing. The tablet is placed between two jaws that crush the tablet. The machine measures the force applied to the tablet and detects when it fractures. Although compressive force is applied to the tablet, along the diameter of the tablet at right angles to the applied force.

6.0)      Disintegration Time 

Unless otherwise stated in the individual monograph, introduce one tablet into each tube and add a disc to each tube. The assembly is suspended in the liquid medium in a suitable vessel, preferably a 1-litre beaker. The volume of liquid is such that the wire mesh at its highest point is at least 15mm below the surface of the liquid, and at its lower point is at least 25mm above the bottom of the beaker. At no time should the top of the basket-rack assembly become submerged. There is a thermostatic arrangement for heating the liquid and maintaining the temperature at 37±2°.

If 1 or 2 tablets fail to disintegrate, repeat the test on 12 additional tablets; not less than 16 of the total of 18 tablets tested disintegrate.

If the tablets adhere to the disc and the preparation under examination fails to comply, repeat the test omitting the disc. The preparation complies with the test if all the tablets in the repeat test disintegrate.

7.0)      Dimension of Tablet:

Length, breadth and thickness are determined by vernier in mm

8.0)      Friability:

The test is applicable to compressed tablets and is intended to determine the physical strength of tablets. For tablets with an average weight of 0.65 gm or less take a sample of whole tablets corresponding to about 6.5gm and for tablets with an average weight of more than 0.65gm take a sample of 10 tablets.

            Dedust the tablets carefully and weigh accurately the required number of tablets. Place the tablets in the drum and rotate it 100 times (25 rpm for 4 minutes). Remove the tablets, remove any loose dust from them and weigh them accurately. The test is run only once unless the results are difficult to interpret or if the weight loss is greater than the target value, in which case, the test is repeated twice and the mean of the three tests is determined.

          Formula: initial wt. – after friability wt. x100 / initial wt.

A maximum loss of weight (From a single test or from the mean of three tests) not greater than 1.0 percent is acceptable for most tablets.

9.0)      Dissolution:

            Apparatus: Paddle

            Medium: 900ml of 0.01 M Hydrochloric acid

            Time: 45 minutes

            Speed: 75 rpm

            Limit: NLT 80% of the stated amount of Allopurinol.

            Withdraw a suitable volume of the medium and filter. Reject the first few ml of filtrate and dilute a suitable volume of the filtrate with dissolution medium. Measure the absorbance of the resulting solution at the maximum at about 250nm. Calculate the content of allopurinol in the medium from the absorbance obtained from a solution containing 0.001 per cent w/v of allopurinol reference standard prepared by dissolving in minimum amount of 0.1 M sodium hydroxide and diluted with the dissolution medium.

10.0)    Leak test:

The apparatus is used to test for the integrity of packed strips, blisters and Alu-Alu Blister pack containing tablets. Ensure apparatus bath is filled with purified water upto mark indicated and add 0.5% crystal violet solution in water. Samples are placed into the desiccators and the lid is placed in position. The pump starts to produce a vacuum 15inHg inside the desiccators and the vacuum is held for 1 minute. The sample remains at the required vacuum level for given time interval buzzer will sound after time is over and will cut off the vacuum pump. As the package is immersed in a colored dye solution the venting of the desiccators will allow any holes to be penetrated by the dye and the contents of the flexible packaging will also be stained with the same coloring material.

Examine all the strips for any leakage by opening the pockets manually. If anyone pocket shows evidence of leakage, reject the sample, stop the Blister / Strip machine and immediately take corrective action.

11.0)    Related substance: Determined by liquid chromatography.

Test solution: Disperse a quantity of the podwered tablets containing 0.01gm of Allopurinol with 10ml of 0.1 M NaOH with the aid of ultrasound and immediately dilute to 200.0ml with mobile phase A, filter.

Reference solution (a): Dilute 1.0ml of the test solution to 100.0ml with the mobile phase A. Further dilute 1.0ml of this solution to 10.0ml with mobile phase A.

Reference solution (b): Dissolve 10 mg of allopurinol impurity A reference standard (5-amino-1H-pyrazole-4-carboxamide RS) in mobile phase A, add 20ml of the test solution and immediately dilute to 100.0 ml with mobile phase A. further dilute 1.0ml of this solution to 100.0 ml with mobile phase A.

Chromatographic system:

  • A stainless steel column 25cmX4.6 mm, packed with octadecylsilane bonded to porous silica (5µm)( such as Nucleosil C18)
  • Mobile phase: A. a mixture of 10 volumes of methanol and 90 volumes of a 0.125 per cent w/v solution of potassium dihydrogen orthophosphate,
  1. a mixture of 30 volumes of methanol and 70 volumes of a 0.125 per cent w/v solution potassium dihydrogen orthophosphate,
  • A gradient programme using the conditions given below,
  • Flow rate: 1ml per minute,
  • Spectrophotometer set at 230nm,
  • Injection volume: 20µl

(in min)

Mobile phase A

(Per cent v/v)

Mobile phase B

(Per cent v/v)

0 100 0
30 0 100
40 0 100
42 100 0

The elution order of the peaks is allopurinol impurity A, allopurinol impurity B, allopurinol impurity C and allopurinol. The retention time for Allopurinol is about 10 minutes.

Inject reference solution (c). The test is not valid unless the resolution between the peaks due to allopurinol impurity A and allopurinol is not less than 3.0.

Inject reference solution (a), (b) and the test solution. Run the chromatogram 5 times the retention time of the principal peak. In the chromatogram obtained with the test solution, the area of the peak due to allopurinol impurity A is not more than the area of the corresponding peak in the chromatogram obtained with reference solution (b) (0.2 per cent). The area of unresolved double peak, the peak at retention time of about 6.1 minutes is not more than twice the area of the principal peak in the chromatogram obtained with reference solution (a) (0.2 per cent). The area of any other secondary peak is not more than the area of the principal in the chromatogram obtained with the reference solution (a) (0.1 per cent). The sum of the area of any other secondary peaks is not more than 3 minutes the area of the principal peak in the chromatogram obtaine with reference solution (a) (0.3 Per cent) .Ignore any peak with an area less than 0.2 times the area of the principal in the chromatogram obtained with reference solution (a) (0.02per cent).

12.0)    Assay: Determined by UV-Spectrophotometer.

Weigh and powder 20 tablets. Disperse a quantity of the powder containing 0.1 gm of allopurinol with 20ml of 0.05M NaOH for 15 to 20 minutes, add 75ml of 0.1 M HCl shake for 10 minutes, add sufficient 0.1 M HCl to produce 250.0ml, filter. Dilute 5.0ml of this filtrate to 250.0ml with 0.1 M HCl. Measure the absorbance of the resulting solution at the maximum at about 250nm using 0.1 M HCl as the blank.

Calculate the content of Allopurinol taking 563 as the specific absorbance at 250nm.

Formula for calculation:

Abs. of test         1000            250                250

  —————-–X———–X—————-X——–XAverage weight

563                   100       Weight of test      5

Acceptance criteria: 92.5%-107.5%


            Perform the test according to requirements of IP,

Total aerobic Microbial count (TAMC): NMT 103 CFU/g

Total combined yeasts/Moulds count (TYMC): NMT 102 CFU/g

Pathogens: in 1gm drug.

Escherichia Coli – Should be absent

Pseudomonas aeroginosa – Should be absent

Salmonella – Should be absent

Staphylococcus aureus– Should be absent



Wt.: Weight

mg: Miligram

ml: Milileter

STD: Standard

inHg: Inch of Mercury

rpm: Rounds per minute

CFU: Colony forming unit

NaOH: Sodium hydroxide

OPA: Orthophosphoric acid