STP for Paracetamol and Diclofenac potassium tablets

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%
25mg or More 5%

4.0)      Identification Test:

In the assay the principal peaks in the chromatogram obtained with the test solution corresponds to the peaks in the chromatogram obtained with the reference solution.

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)      Assay: Determined by liquid chromatography.

Reference solution: Weigh accurately about 162.5 mg of Paracetamol reference standard, and 50 mg of Aceclofenac reference standard in 100ml volumetric flask, dissolve in and dilute to the mark with mobile phase. Shake well and further dilute 2 ml to 25 ml with mobile phase. Shake well and filter through 0.45µm nylon filter.

Test preparation: Weigh accurately about equivalent to 165 mg of Paracetamol from crushed powder of 20 tablets in 100 ml volumetric flask, add 50 ml of mobile phase, sonicate for 5 minutes, cool to room temperature and dilute to the mark with mobile phase, filter. Shake well and further dilute 2 ml to 25 ml with mobile phase, shake well and filter through 0.45µm nylon filter.

Procedure: Inject separately standard and test preparation. Inject five replicate injection of working standard and two replicate injection of test preparation.RSD of replicate injection should not more than 2%. Calculate the assay of Paracetamol and Aceclofenac by comparison to peak area of standard preparation.

Chromatographic condition:

Mobile phase: – Methanol + Water + G.A.A. = 80: 20 +0.01ml; degas,

Column: – C-18, (150 x 4.6mm, 5µm);

Wavelength: – 280nm;

Flow rate: – 1.8ml per minute;

Injection volume: – 20µl


Area of test     Wt. of STD       2        100         25

——————-X————–X——X——–X——–X Average. Wt. x potency of w.s.

Area of STD          100            25      test wt.     2

            Acceptance criteria: 90.0%-110.0%