Dissolution :

Medium:  0.1N hydrochloric acid, 900 ml.

Apparatus: 2 (Paddle)

Speed: 75 rpm.

Time:  30 minutes.

Dissolution procedure:

  1. Set dissolution apparatus by programming temperature, rotation and run time at 37°C±0.5°C, 75 rpm and 30 minutes respectively.
  2. Place 900 ml of dissolution medium into each of the six vessels of the dissolution apparatus.
  3. Assemble the apparatus and equilibrate the dissolution medium at 37°C±0.5°C.
  4. Place one tablet into each of six vessels and allow the tablet to the bottom of the vessels before starting the rotation of the paddles.
  5. Immediately start the rotation of the paddles at the speed of 75 rpm for 30 minutes.

                                   Note: Keep the vessel covered during the test.

  • After 30 minutes, withdraw the 10 ml aliquots from a zone midway between the surface of the dissolution medium and top of the paddles, from each of six vessels.

Determine the amount of Calcium Carbonate (CaCO3) dissolved by employing the following method.

Lanthanum chloride solution: Prepare a solution of lanthanum chloride in 0.1 N Hydrochloric acid having a concentration of about 50 mg per ml.

Blank: Lanthanum chloride solution and 0.1 N Hydrochloric acid (1:9).

Standard stock solution: Dissolve an accurately weighed quantity of calcium carbonate in 0.1 N Hydrochloric acid and dilute quantitatively and stepwise if necessary, with 0.1 N Hydrochloric acid to obtain a solution having a known concentration of about 100 µg of calcium per ml.

Standard solution: Into separate 100 ml volumetric flasks, each containing 10 ml of Lanthanum chloride solution separately pipette 3, 4, 5 and 6 ml portions of standard stock preparation. Dilute each with 0.1 N Hydrochloric acid to volume and mix to obtain standard preparation having known concentrations of about 3, 4, 5, and 6 µg of Calcium per ml, respectively.

Sample solution: Filter a portion of the solution under test. Pipette a volume of the filtrate, estimated to contain about 1 mg of calcium, into a 250 ml volumetric flask, add 25 ml of Lanthanum chloride, solution dilute with 0.1 N Hydrochloric acid to volume and mix.

Mode: Atomic absorption spectrophotometry.

Analytical wavelength: 422.8 nm.

Lamp: Calcium hollow-cathode.

Flame: Air-acetylene.

Analysis: Concomitantly determine the absorbance of the standard solution and the sample solution against the blank. Construct a standard curve by plotting absorbance versus Calcium concentrations of the standard solution and then from it obtain the concentration C, in µg of calcium per ml, of the test solution.

Calculation: Calculate the percentage of Calcium Carbonate (CaCO3)dissolved by the formula:

(Mr / Ar) x (C x D x V/L) x 100

Mr = Molecular weight of Calcium Carbonate 100.09.

Ar = Atomic weight of Calcium 40.08.

D= Dilution factor for the sample solution.

V = Volume of medium, 900 ml.

L = Label claim (mg/tablet).

Interpretation: The requirements are met if the quantities of active ingredient dissolved from the pooled sample conform to the accompanying acceptance table for a pooled sample. Continue testing through the three stages unless the results conform at either S1 or S2.

Acceptance Table

Stage Number Tested Acceptance Criteria
S1 6 Each unit is not less than Q+5%.  
S2 6 Average of 12 units (S1+S2) is equal to or greater than Q and no unit is less than Q-15%.  
S3 12 Average of 24 units (S1+S2+S3) Equal to or greater than Q, not More than 2 units are less than Q-15% and no unit is less than Q-25%.

                                     Test Reading       Std. dilution        Potency (in %)

        Calculation: = ———————-x ——————-x ———————— x 100

                                     Std.  Reading       Test dilution               100

Bhanu Pratap Singh


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