PRACTICAL 5 : CONTENT OF IBUPROFEN (ASSAY)

Objective: 

To identify the content of ibuprofen by assay.

Experimental Method:

1.      20 Ibuprofen tablets selected at random previously were weighed by using an electronic weighing balance and powdered using mortar and pestle.
2.      A quantity of powder containing 0.5 g ibuprofen was extracted with 20 ml chloroform for 15 minutes and filtered through a filter paper.
3.         The residue was washed with 3 × 10 ml chloroform and the combined filtrate was gently evaporated just to dryness in a current of air. The residue was dissolved with 100 ml ethanol (96%) previously neutralized to phenolphthalein solution.
4.      The solution was titrated with 0.1 M sodium hydroxide to end point with phenolphthalein solution as the indicator. The content of ibuprofen was calculated if each ml of 0.1 M sodium hydroxide is equivalent to 0.02063 g of C₁₃H₁₈O₂.

Result and Calculations:

Discussion:

              

      The percentage of deviation is respectively large, which is 36.04%. This might be caused by some errors done during the experiment. Error might be done during the powder of ibuprofen tablets using mortar and pestle. Some powder might be displaced out of the mortar when too much force was applied when powdering the tablets which lead to decrease in mass of the total ibuprofen powder which causes inaccurate results. Besides, error might be done when the process of filtration was not being conducted properly as filter paper of smaller size was used and the residue is not being filtrated completely before proceeding to the next step. Another error might occur when drying the filtrate. The filtrate might be over dried and the ibuprofen evaporated, causing the mass of ibuprofen decreased and leading to inaccurate results. Apart from this, error might be done during titration when the process was stopped and the reading of volume was obtained when the end-point was not being reached which leads to inaccurate volume of NaOH needed. Parallax errors might also occur throughout the experiment when the eye level was not perpendicular to the reading scale on the measuring cylinder while measuring the solution. Beside this, the ibuprofen tablets used were expired, which might have reduced amout of ibuprofen content.

        To overcome the errors above, some precaution steps should be taken. Firstly, powdering of ibuprofen tablets should be done carefully by applying force enough to powder the tablet but not causing the powder to spill out of the mortar. Besides, the filtration process should be carried out more properly by using filter paper of appropriate size and patiently wait until all residue being filtered. During drying of filtrate using a hot gun, drying should be stopped once the liquid being evaporated but not until the white residue which is the ibuprofen being evaporated. Apart from this, the titration should only be stopped when the end point which is when the solution turns pale pink, has reached. Parallax errors should be avoided by placing the eye level perpendicular to the reading scale on the measuring cylinder while measuring volumes of solutions. Besides, ibuprofen tablets used must not be expired to obtain a more ideal results.

Conclusion:

The percentage of deviation is 36.03% which means that the content of ibuprofen is 63.97% of the labeled content.