Determination of Wavelength of maximum absorbance (λmax) of Paracetamol.

 Experiment

Object:

Determination of  the absorption maxima (λmax) of Paracetamol.

1. Theory:

1.  wavelength of maximum absorbance (λmax):
2.  The extent to which a sample absorbs light depends upon the wavelength of light. The wavelength at which a substance shows maximum absorbance is called absorption maximum or λmax. 
3. The value of λmax is important for several reasons. 
4. • This wavelength is characteristic of each compound.
5. • It provides information on the electronic structure of the analyte 
6. •It ensures highest sensitivity and minimize deviations from Beer's Law.
7.  We can determine λmax by plotting absorbance vs wavelength in graph. 
8. 
   
9. Preparation of stock solution:
10. 
    
11. 1. 5 mg paracetamol powder were weighed by electronic balance 
12. 2. This powder was taken in a 50 ml volumetric flask and was filled with distilled water upto the mark. 
13. 3. The flask was shacked well until the paracetamol powder was dissolved. This solution was the stock solution. 
14. Preparation of working stock: Take 10 ml of stock solution and dilute up to 100ml with distilled water.

1.  Procedure: 

1. 1. Set the spectrophotometer wavelength to 200 nm and with a cuvette containing distilled water to set the instrument reference level. 
2. 2. Place the cuvette containing the prepared dilution in the sample compartment. Record the absorbance. 
3. 3. Repeat steps 2 at wavelength increments of 200 nm up to 400 nm and record absorbance at each wavelength setting. 
4. 4. Plot the results as absorbance against wavelength.
5. 5. From the graph note the wavelength of maximum absorbance for this solution. 

1. Data Table: 
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3. Result: