Sensory ppt
- 2. INTRODUCTION Spectroscopy –study of interaction between of electromagnetic radiation with matter
- 3. There are two ways of interaction between electromagnetic radiation and matter can takes place
- 5. UV SPECTROSCOPY It is also known as electronic spectroscopy. Uv ranges from 190-400nm Valence electrons absorb the energy thereby molecules undergoes transition from ground state to excited state.
- 6. BEER –LAMBERT LAW: This law states that amount of light absorbed is directly proportional to the concentration of absorbing substance and to thickness of absorbing material. A = abc or log(Iₒ/I) =abc Where A is absorbance b is path length (cm) c is concentration (M) a is molar absorptivity constant(1/Mcm) Molar absorptivity is the charateristic of a substance that tells how much of light is absorbed at a particular wave length.
- 9. σ→ σ⃰ σ electron from bonding orbital is excited to corresponding antibonding orbital σ⃰ . The energy require is large for the transition. The organic compounds in which all the valence shell electron are involved in the formation of σ bond do not show absorption in uv region. This transition is observed with saturated compounds Eg :Methane has C-H bond only and can undergo σ- σ⃰ transistion and shows absorption maxima at122 nm. The usual spectroscopic technique cannot be used below 200 nm. To study this high energy transition the entire region should be evacuated Here, the excitation occurs with net retention of electronic spin. This region is less informative.
- 10. n→σ⃰ Saturated compounds containing one hetero atom with unshared pair of electrons like O,N,S and halogen capable of n→σ⃰ transitions These transiton require low energy than σ→ σ⃰ transitions. Eg methyl chloride.
- 11. π→π⃰ π electron in a bonding orbital is excited to corresponding antibonding orbital π⃰. Energy required is less when compared to n- σ⃰ Compounds containing multiple bonds like alkenes,alkynes,carbonyls,nitiriles,aromatic componds. etc undergo π→π⃰ transitions. Absorption usually occurs in the normal uv spectrophotometer.
- 12. n→π⃰ An electron from non bonding electron is promoted to antibonding π⃰ orbital . Compounds containing double bonds involve in hetero atom (C=O,N=O) undergo such transition. The transition requires minimal energy
- 15. Case study
- 16. Application Detection of impurities. Qualitative analysis. Quantitative analysis.
- 17. Mass spectroscopy Mass spectrometry is an instrumental technique in which sample is converted to rapidly moving positive ion by electron bombardment and charged particles are separated according to their masses. It measures the molecular weight of compound by the ratio of mass to charge
- 19. Basic principles of MS
- 21. COMPONENTS OF MS
- 22. INSTRUMENTATION
- 23. Application Used in the field of proteomics. Used in phytochemical screening of unknown compound . Used in detection of pesticides in food . Used in pharmaceutical analysis.