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 = * b * cε

where is the wavelength-dependent ε molar absorptivity coefficient with units of M-1 cm-

1.

As, and b, both are constant, then it can be written that, A Ɛ 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.

0 2 4 6 8 10 1202468

1012

f(x) = xR² = 1

Standard Calibration Curve

Concentration (µg/ml)

Abso

rban

ce

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

Procedure:

Preparation of stock solution:

1. 5 mg aceclofenac powder were weighed by electronic balance2. 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 02 0.5 9.5 53 1 9 104 1.5 8.5 155 2 8 206 2.5 7.5 257 3 7 308 3.5 6.5 359 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 powder4. 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.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 Absorbance0 0

5 0.909

10 0.12515 0.199

20 0.240

25 0.329

30 0.346

35 0.378

40 0.428

Sample ( 16.67) 0.194

0 5 10 15 20 25 30 35 40 450

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.09

0.125

0.199

0.24

0.3290.346

0.378

0.428f(x) = 0.00990714285714286 x + 0.0439642857142857R² = 0.979901458160467

Potency test curve of Aceclofenac tablet

Absorbance Linear (Absorbance)

Concentration

Abso

rban

ce

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

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.