Determination of the potency of Aceclofenac tablet by UV-Spectrophotometric method

1. Name of the Experiment: Determination of the potency of Aceclofenac tablet by UV-
Spectrophotometric method
Principle:
When a beam of radiation (light) passes through a substance or a solution, some of the
light may be absorbed and the remainder transmitted through the sample. The ratio of
the intensity of the light entering the sample (Io) to that exiting the sample (I) at a
particular wavelength is defined as the transmittance (T). The absorbance (A) of a
sample is the negative logarithm of the transmittance.
A = - log (T)
Figure: Absorption of light by a sample
Beer-Lambert Law
The absorbance of a sample at a given wavelength is proportional to the absorptivity of
the substance (a constant at each wavelength), the path length (the distance the light
travels through the sample) and the concentration of the absorbing substance. In these
cases the Beer-Lambert Law holds:
A = a * b * c where a = the absorptivity of the substance
b = path length
c = concentration of the substance
When working in concentration units of molarity, the Beer-Lambert law is written as:
A = ε * b * c
where ε is the wavelength-dependent molar absorptivity coefficient with units of M-1 cm-
1.
As, Ɛ and b, both are constant, then it can be written that, A ∝ c
If, absorbance (A) is plotted on Y-axis against concentration (c) on X-axis, a linear curve
is obtained. It is called standard calibration curve. It follows the equation of a straight
line, y = mx+c.
If the absorbance of an unknown sample is then measured, the concentration of the
absorbing component can be determined from this graph.

2. Aceclofenac: Aceclofenac is an NSAID (Non-Steroidal Anti-Inflammatory Drug). It is an
acidic drug which has been used for its analgesic and anti-inflammatory action. It is a non-
selective COX inhibitor.
Figure: Structure of Aceclofenac
Indication:
Relief of pain and inflammation in
 Rheumatoid arthritis
 Osteoarthritis
 Ankylosing spondylitis
Apparatus:
 UV Spectrophotometer
 Test tube
 Pipette
 Measuring cylinder
 Volumetric flask
 Electronic balance
 Mortar and pestle
 Filter paper
Reagents:
 Standard aceclofenac powder
 Aceclofenac tablet (Elixir Company)
 95% ethanol
y = x
R² = 1
0
2
4
6
8
10
12
0 2 4 6 8 10 12
Absorbance
Concentration (µg/ml)
Standard Calibration Curve

3. Procedure:
Preparation of stock solution:
1. 5 mg aceclofenac powder were weighed by electronic balance
2. This powder was taken in a 50 ml volumetric flask and was filled with 95% ethanol
upto the mark.
3. The flask was shaked well until the aceclofenac powder was dissolved. This solution
was the stock solution.
Preparation of working standard:
1. 9 test tubes were taken, were marked serially from 1-9 and were kept in a test tube
holder.
2. Test tube marked 1 was taken and was added with 10 ml 95% ethanol. No stock
solution is added in this test tube.
3. Test tube marked 2 was taken and was added with 0.5 ml stock solution and 9.5 ml
95% ethanol.
4. The dilution process was conducted for the rest of the test tubes.
Test Tube
Number
Stock Solution
(ml)
95% Ethanol
(ml)
Concentration
(mcg/ml)
1 0 10 0
2 0.5 9.5 5
3 1 9 10
4 1.5 8.5 15
5 2 8 20
6 2.5 7.5 25
7 3 7 30
8 3.5 6.5 35
9 4 6 40
Preparation of Sample Solution:
1. 5/10 aceclofenac tablets (Elixir Company) were taken and the individual weight of
each tablet were measured by electronic balance.
2. The average weight was determined which is 226 mg.
3. Tablets were taken and were crushed in mortar and pestle
100 mg aceclofenac is present in 226 mg of powder
 5 mg aceclofenac is present in 11.3 mg of powder
4. 11.3 mg of powder was weighed from the mortar and pestle by electronic balance and
was kept in a 50 ml a volumetric flask.
5. 95% ethanol was added upto the mark.
6. Then the solution was filtered.

4. 7. 1 ml of the filtrate was taken in the test tube; 4 ml or 9 ml 95% ethanol was added in
the two test tubes respectively.
Calibration of UV Spectrophotometer:
1. The UV spectrophotometer was turned on and waited for the calibration to be
completed.
2. 2/3rd of the cell was filled with 95% ethanol, the wavelength was set at 275 nm and
press the auto-zero button.
Determination of absorbance for the working standard and the sample solution:
1. Test tube 1 was taken and the cell was filled with it.
2. The cell was placed into the sample holder and the absorbance was measured.
3. Same way, the absorbance of the working standard and the sample were determined.
Calculation:
Calculation of the experimental/calculated value:
From the standard curve, the following equation is obtained:
Concentration Absorbance
0 0
5 0.909
10 0.125
15 0.199
20 0.240
25 0.329
30 0.346
35 0.378
40 0.428
Sample ( 16.67) 0.194

5. Experimental concentration value, x = y-c/m
= 0.194-0.044/0.009
= 16.67
Calculation of the theoretical value:
50 ml stock solution contains 5 mg Aceclofenac
 1 ml stock solution contains 5/50 mg Aceclofenac
So, concentration of the stock solution = 5mg/50 ml = 0.1 mg/ml = (0.1*1000) µg/ml = 100
µg/ml
Again,
5/10 ml diluted solution contains 100 µg Aceclofenac
 1 ml diluted solution contains 100/5 or 100/10 µg Aceclofenac
= 20 or 10 µg/ml
So, Theoretical concentration value = 20 or 10 µg/ml
0.09
0.125
0.199
0.24
0.329
0.346
0.378
0.428
y = 0.0099x + 0.044
R² = 0.9799
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 5 10 15 20 25 30 35 40 45
Absorbance
Concentration
Potency test curveof Aceclofenac tablet
Absorbance Linear (Absorbance)

6. Determination of Potency:
Potency = Experimental value/Theoretical value *100
= (16.67/10)*100
= 166.7%
Result: The potency of supplied aceclofenac tablet is 166.7%
Comment: According to USP specification of potency for tablet should be 100±10. In our
experiment, potency of aceclofenac tablet was 166.7% which is not comply with
specification. This study provides the knowledge of R2 value. R2 value of this study is
0.9799 which is near to 1. So drug didn’t pass the test.
Reason:
 Drug didn’t pass the test due to experimental error.
 UV-spectrophotometer didn’t work properly.
 There may be some error to prepare the sample solution.
Precaution:
 Apron must be worn.
 All equipments and instruments were handled properly.
 Standard and sample ingredients were weighed and handled properly.