Beers Law deviations.

The slide contains beers law deviations and its applications.
presented by: P.Naresh. M.Pharm (Department of pharmaceutical analysis.).

1. BEERS LAW DEVIATIONS A Seminar as a part of Curricular requirement for I year M.Pharm I Semester Presented by P.Naresh Reg.No.20L81S0701 Under the Guidance/Mentorship of Dr. P. Ramalingam, M.Pharm., Ph.D ., R&D Director

2. Contents Applications Types of deviation References

3. Beer Lamberts Law It’s law which state ,The absorptivity of radiation by analyte molecules is directly proportional to the concentration of the solution and path length sample cells . A ∞ b c Σ = molar absorption co-efficient A = ĸ bc A= Absorbance A = Σbc b =Pathlength C=Concentration

4. Applications Estimation of the concentration of drug’s. Used for qualitative analysis . Used for quantitative analysis .

5. Types of Deviation There are three types of deviations- The Real deviation / True deviation Spectral deviation Chemical deviation

6. A)Real Deviation/True Deviation The beers law is successfully describing absorption behaviour of dilute solution only so, Be ers law is valid at low concentration. In some time we can observed real deviation. If concentration double , the absorbance is not relatively double because of real deviation mainly observed in high concentration analyte.

7. Cntd... At low concentrations Re fractive index is not significant , concentrations Of sample from 10 6 to 10 3 M, η =1 At high concentrations Refractive index is significant , concentrations of sample above 10 3 M, η <1 So ,Here observed Non linearity curve .

8. B) Spectral Deviation

9. Cntd .. The graph contain the narrow band width as a monochromatic radiation The graph contains the larger band width as a polychromatic radiation, this leads to deviation from the beer’s law.

10. Cntd… Sometimes we can also observed spectral deviation due to the stray radiation Stray radiation means unwanted radiation , which reaches to the detector, that resulting from the R eflection , R efraction , S cattering of light by the solid particles and other type of molecules. Spectral deviations mainly due to the P olychromatic radiation, S tray radiation .

11. C)Chemical Deviation Chemical deviation arise if the absorbing species undergo chemical changes such as Association molecules Complex formation Dissociation molecules Hydrogen bonding Hydrolysis Ionization(or) polymerization pH changes in sample

12. Cntd .. When the concentration of the sample increases, the molecule can associate to form the D imers and P olymers, which will again have different absorption. In order to prevent the chemical deviation, we have to check whether the sample is undergoing association (or) dissociation and we have to fix the pH by using suitable buffer systems.

13. References 1. Sharma Y. Elementary organic spectroscopy: principles and chemical application. Chand and Company Ltd, New Delhi, India. 2009;23. 2. Chatten LG. Pharmaceutical Chemistry: Instrumental Techniques: M. Dekker; 1966. 3. Fifield FW, Kealey D. Principles and practice of analytical chemistry: Blackwell Science Hoboken; 2000. 4. Rao NM, Bagyalakshmi J, Ravi T. Development and validation of UV-Spectroscopic method for estimation of Voglibose in bulk and tablets. J Chem Pharm Res. 2010;2(2):350-56.