Practical 4 - Content of Ibuprofen (assay)

Introduction:

Ibuprofen is a non-steroidal anti-inflammatory drug (NSAID). It helps to reduce hormones that can cause inflammation and pain in the body. It is mostly used to treat pain and inflammation caused by many conditions such as headache, toothache and back pain. Ibuprofen also used to reduce fever.

Ibuprofen tablets are available in different strengths range from 200 mg to 800 mg.

Objective:

1.       To determine the given formulation of Ibuprofen.

Apparatus and materials:

1.       Conical flask

2.       Measuring cylinder

3.       Measuring balance

4.       Filter funnel

5.       Filter paper

6.       Hairdryer

7.       Retort stand

8.       Burette

9.       Pestle and mortar

10.   20 Ibuprofen tablets with strength of 400 mg.

11.    Chloroform

12.   Ethanol

13.   Phenolphthalein solution

14.   0.1M sodium hydroxide solution

Procedure:

1.       20 Ibuprofen tablets with 400 mg strength are selected at random and weighed. The total weight is measured. The tablets are then powdered.

2.       0.6467 g of the powder containing 0.5 g Ibuprofen is extracted with 20 ml chloroform for 15 minutes in fume hood. Then, it is filtered through a sintered glass crucible.

3.       The residue is washed with 3 x 10 ml chloroform and filtered again. The combined filtrate is gently evaporated using a hairdryer just to dryness in a current of air. The residue is dissolved in 100 ml with ethanol (96%) previously neutralized to phenolphthalein solution.

4.       The solution is titrated with 0.1M sodium hydroxide to end point with phenolphthalein solution as the indicator until the solution turns pink in colour. The content of ibuprofen is calculated is each ml of 0.1M sodium hydroxide is equivalent to 0.02063 g of C₁₃H₁₈O₂.

Results:

Total weight = 10.3475 g

Content of ibuprofen in 20 tablets = 0.4 g x 20

                                                                    = 8 g

10.3475 g of total weight contains 8 g of ibuprofen.

So, 0.6467 g from the total weight contains 0.5 g of ibuprofen.

Initial reading of burette = 0.00 ml of 0.1M sodium hydroxide

Final reading of burette = 22.3 ml 0.1M sodium hydroxide

1 ml of 0.1M sodium hydroxide is equivalent to 0.02063 g of C₁₃H₁₈O₂

So, 22.3 ml x 0.02063 g = 0.46 g Ibuprofen is present

Percentage error = (0.46 g – 0.5 g) / 0.5 g x 100 % = -8 %

                                                                                  = 8 %

Discussion:

In this experiment, the final result which is 0.46 g of Ibuprofen is obtained. It is slightly different compared to the actual weight which is 0.5 g. 8 % of percentage error determines that during the experiment, there are some errors involved. It includes uneven crushing of tablets resulting in not uniform powder and reduces powder flow thus not easy to dissolve. Second error is parallax error when measuring the chloroform. Eyes are not perpendicular to the measure and causing inaccurate measurement.  Error also occurred during the extraction process when the solution is not placed in fume hood causing it to evaporate. This will affect the content of ibuprofen present in the solution

Conclusion:

In conclusion, the weight of ibuprofen obtained is 0.46 g and the percentage error is 8 %. Thus, this test is suitable to determine the accurate near value of ibuprofen content but has to comply with some conditions to avoid error and to obtain good result. 

References:

1. http://web1.caryacademy.org/facultywebs/gray_rushin/StudentProjects/CompoundWebSites/1998/Ibuprofen/structibu.htm [structure of Ibuprofen]

2. BNF-65 Ed, BNF publications. (pg 671)