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Spectroscopy and UV VIS spectrophotometer (1).pptx
- 2. What Is Spectroscopy? Spectroscopy is a technique that uses the interaction of energy with a sample to perform an analysis Deals with production, measurement and interpretation of spectra arising from the interaction of electromagnetic radiation with matter What Is a Spectrum? The data that is obtained from spectroscopy is called a spectrum. A spectrum is a plot of the intensity of energy detected versus the wavelength of the energy What Information Is Obtained? A spectrum can be used to obtain information about atomic and molecular energy levels, chemical bonds and interactions of molecules. Often, spectra are used to identify the components of a sample (qualitative analysis). Spectra may also be used to measure the 2
- 3. Spectroscopy types depend upon Species to be analyzed (molecular or atomic spectroscopy) Type of radiation-matter interaction (absorption, emission, diffraction) Region of electromagnetic spectrum (UV, Visible, IR etc.) Properties of light Particles of energy that move through space with wave like properties. Energy associated with ray of light is not distributed continuously but in discrete packets along electric and magnetic field Light has dual nature Particulate (absorption and emission) Wavelike (interference, diffraction, refraction) 3
- 4. Types of Spectroscopy 4 1. UV-Vis Spectroscopy 2. Atomic Emission Spectroscopy 3. Atomic Absorption Spectroscopy 4. Infrared Spectroscopy 5. Mass Spectroscopy 6. Laser Spectroscopy
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- 8. 8 Lambert’s law The proportion of incident light absorbed by a transparent medium is independent of the intensity of the light (provided there is no other physical or chemical change to the medium). Therefore, successive layers of equal thickness will transmit an equal proportion of the incident energy Lambert’s law expressed as: I/Iо =T where, I = the intensity of the transmitted light I о = the intensity of the incident light T = transmittance
- 9. Beer’s law The absorption of light is directly proportional to both the concentration of the absorbing medium and the thickness of the medium in the light path A combination of the two laws (Lambert-Beer Law) defines the relationship between absorption (A) and transmittance (T) A = log I о /I A = εb c where, ε = absor ptivity consta nt b = 9
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- 12. Minimum requirements of UV-VIS Spectrophotometer A source of radiation of appropriate wavelength Means of isolating light of single wavelength – a monochromator A means of introducing the test sample into light beam A means of detecting and measuring the light intensity 12
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