Title
Content of ibuprofen
(assay)
Aim
To determine the
content of ibuprofen
Introduction
Ibuprofen
is a painkiller, which is available over-the-counter, without a prescription.
It is one of a group of painkillers called non-steroidal anti-inflammatory
drugs (NSAIDs), and can be used to ease mild to moderate pain such as
toothache, migraines and period pain, to control a fever which is in high
temperature, also known as pyrexia, to ease pain and inflammation caused by
rheumatic diseases and musculoskeletal disorders and to ease pain and swelling
caused by sprains and strains, such as sports injuries.
Ibuprofen
should be avoided by people with certain health conditions, such as a current
or recent stomach ulcer, or a history of bad reactions to NSAIDs. It should be
used with caution by older people, and people with certain health conditions,
including asthma or kidney or liver problems.
Ibuprofen
is made by many different companies, under many different brand names and in a
wide range of forms, including tablets or caplets, gels, sprays and liquids. The
dosage prescribed usually for adult and child over 12 years, initially
300-400mg, 3-4 times daily. The dosage will increased if necessary to maximum
2.4 g daily. The maintenance dose of 0.6-1.2g daily may be adequate. The dosage
given of Ibuprofen to children who had pain and fever are different in age
range. Usually Ibuprofen is marketed which 200 mg ibuprofen in a tablet. In
oral suspension the content of ibuprofen is 100mg/5ml.
Figure 1: Structure of
ibuprofen
Apparatus
Weighing boat,
electronic balance, spatula, conical flask, beaker, dropper, measuring
cylinder, filter funnel, filter paper, glass rod, hair dryer, burette,
titration burette clamps.
Materials
20 tablets of
Ibuprofen, 50 ml chloroform, 100 ml ethanol, phenolphthalein, 0.1 M sodium
hydroxide.
Procedure
1. 20 Ibuprofen Tablets
are weighed and powdered previously selected at random.
2. Quantity of powder
containing 0.5 g ibuprofen is extracted with 20 ml chloroform for 15 minutes
and filtered through a sintered glass crucible (BS Porosity No. 1).
3. The residue is
washed with 3 ×
10 ml chloroform and the combined filtrate is evaporated gently just to dryness
in a current of air. The residue is dissolved in 100 ml ethanol (96%)
previously neutralized to phenolphthalein solution.
4. The solution is
titrated with 0.1 M sodium hydroxide to end point with phenolphthalein solution
as indicator. The content of ibuprofen is calculated as each ml of 0.1 M sodium
hydroxide is equivalent to 0.02063 g of C13H18O2.
Result
and calculations
Observation:
The solution turns from colourless to pink in titration.
Materials
|
Weight (g)
|
Powder of Ibuprofen + weighing boat
|
11.1400
|
Weighing boat
|
3.2000
|
Powder of Ibuprofen
|
7.9400
|
Weight of powder of 20
tablet Ibuprofen: 7.9400 g
1 tablet contain 200 mg
Ibuprofen
20 tablet contains 20 x
200 mg Ibuprofen = 4000 mg = 4 g Ibuprofen
4 g Ibuprofen contains
7.9400 g of tablet powder
0.5 g Ibuprofen
contains:
0.50g/4.00g= x/7.94g
x = 0.9925 g of powder
contain 0.5 g Ibuprofen
Thus, 0.9925 g of
tablet powder was weighed and dissolved with 20 ml chloroform.
NaOH + C13H18O2 C13H17ONa
+ H2O
Initial burette reading
of 0.1 M NaOH = 30.0 ml
End point reading of
0.1 M NaOH = 50.1 ml
Volume of 0.1 M NaOH = 50.1
ml – 30 ml = 20.1 ml
No. of mole of NaOH used in titration =MV/1000
If 1 ml 0.1 M NaOH is
equivalent 0.02063 g
20.1 ml 0.1 M NaOH is
equivalent to 0.02063 g x 20.1 ml = 0.4147 g
Thus, the content of
ibuprofen is 0.4147 g.
Discussion
Percentage of deviation
= (experiment value-theoretical value)/ theoretical value x 100%
Theoretically, 0.9925 g
of Ibuprofen tablet powder contains 0.5 g Ibuprofen
Percentage of deviation
= (0.4147g-0.5g)/0.5g x 100% = 17.06%
The percentage of deviation is
not too large, which is 17.06%. This might be caused by some errors done during
the experiment. Errors 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 amount 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 17.06% which means that
the content of ibuprofen is 82.94% of the labeled content. Besides, the errors
must be prevented to obtain more accurate results.
Reference
