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SPECTROSCOPY. سپکتروسکوپی. Downloaded from www.pharmacy123.blogfa.com. Definition :. Spectroscopy - The study of the interaction of electromagnetic radiation with matter. Electromagnetic radiation :. An oscillating electric and magnetic field which travels through space
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SPECTROSCOPY سپکتروسکوپی Downloaded from www.pharmacy123.blogfa.com
Definition : • Spectroscopy - The study of the interaction of electromagnetic radiation with matter . دیپارتمنت کیمیای فارمسی وکنترول ادویه
Electromagnetic radiation : • An oscillating electric and magnetic field which travels through space • A discrete series of “particles” that possess a specific energy but have no Mass BOTH! دیپارتمنت کیمیای فارمسی وکنترول ادویه
Properties of Light • Light can be thought of as a wave or particle. • The wavelength, , is the distance between crests of a wave (m) • The frequency, , is the number of oscillations per second (Hz) دیپارتمنت کیمیای فارمسی وکنترول ادویه
Introduction of Spectrometric Analyses The study how the chemical compound interacts with different wavelengths in a given region of electromagnetic radiation is called spectroscopy or spectrochemical analysis. The collection of measurements signals (absorbance) of the compound as a function of electromagnetic radiation is called a spectrum. دیپارتمنت کیمیای فارمسی وکنترول ادویه
Energy Absorption The mechanism of absorption energy is different in the Ultraviolet, Infrared, and Nuclear magnetic resonance regions. However, the fundamental process is the absorption of certain amount of energy. The energy required for the transition from a state of lower energy to a state of higher energy is directly related to the frequency of electromagnetic radiation that causes the transition. دیپارتمنت کیمیای فارمسی وکنترول ادویه
Regions of the electromagnetic spectrum : دیپارتمنت کیمیای فارمسی وکنترول ادویه
absorption transmission refraction reflection scattering Interaction of e.m.r. with Matter • Interaction of electromagnetic radiation with matter • The wave-length, l, and the wave number, v’, of e.m.r. changes with the medium it travels through, because of the refractive index of the medium; the frequency, v, however, remains unchanged • Types of interactions • Absorption • Reflection • Transmission • Scattering • Refraction • Each interaction can disclose certain properties of the matter • When applying e.m.r. of different frequency (thus the energy e.m.r. carried) different type information can be obtained . دیپارتمنت کیمیای فارمسی وکنترول ادویه
Absorption and Emission of Photons دیپارتمنت کیمیای فارمسی وکنترول ادویه
Spectral Distribution of Radiant Energy Wave Number (cycles/cm) X-Ray UV Microwave Visible IR 200nm 400nm 800nm Wavelength (nm) دیپارتمنت کیمیای فارمسی وکنترول ادویه
Electromagnetic Radiation V = Wave Number (cm-1) l = Wave Length C = Velocity of Radiation (constant) = 3 x 1010 cm/sec. u = Frequency of Radiation (cycles/sec) The energy of photon: h (Planck's constant) = 6.62 x 10-27 (Ergsec) C = u دیپارتمنت کیمیای فارمسی وکنترول ادویه
Spectral Properties, Application and Interactions of Electromagnetic Radiation Type Radiation Type spectroscopy Type Quantum Transition Energy Wave Number V Wavelength λ Frequency υ Kcal/mol eV cm-1 cm Hz Gamma ray Gamma ray emission Nuclear X-ray absorption, emission Electronic (inner shell) X-ray Ultra violet Electronic (outer shell) UV absorption Visible IR absorption Infrared Molecular vibration Molecular rotation Microwave absorption Micro-wave Magnetically induced spin states Nuclear magnetic resonance Radio دیپارتمنت کیمیای فارمسی وکنترول ادویه
Excited state ground state n = 1 n = 2 n = 3, etc. energy DE 4f 4d n=4 4p 3d 4s Energy n=3 3p 3s n=2 2p 2s n=1 1s Atomic Spectra • Shell structure & energy level of atoms • In an atom there are a number of shells and of subshells where e-’s can be found • The energy level of each shell & subshell are different and quantised • The e-’s in the shell closest to the nuclei has the lowest energy. The higher shell number is, the higher energy it is • The exact energy level of each shell and subshell varies with substance • Ground state and excited state of e-’s • Under normal situation an e- stays at the lowest possible shell - the e- is said to be at its ground state • Upon absorbing energy (excited), an e- can change its orbital to a higher one - we say the e- is at an excited state. دیپارتمنت کیمیای فارمسی وکنترول ادویه
energy DE n = 1 n = 2 n = 3, etc. 4f 4d n=4 4p 3d 4s Energy n=3 3p 3s n=2 2p 2s n=1 1s Atomic Spectra • Electron excitation • The excitation can occur at different degrees • low E tends to excite the outmost e-’s first • when excited with a high E (photon of high v) an e- can jump more than one levels • even higher E can tear inner e-’s away from nuclei • An e- at its excited state is not stable and tends to return its ground state • If an e- jumped more than one energy levels because of absorption of a high E, the process of the e- returning to its ground state may take several steps, - i.e. to the nearest low energy level first then down to next … دیپارتمنت کیمیای فارمسی وکنترول ادویه
energy DE n = 1 n = 2 n = 3, etc. 4f 4d n=4 4p 3d 4s Energy n=3 3p 3s n=2 2p 2s n=1 1s Atomic Spectra • Atomic spectra • The level and quantities of energy supplied to excite e-’s can be measured & studied in terms of the frequency and the intensity of an e.m.r. - the absorption spectroscopy • The level and quantities of energy emitted by excited e-’s, as they return to their ground state, can be measured & studied by means of the emission spectroscopy • The level & quantities of energy absorbed or emitted (v & intensity of e.m.r.) are specific for a substance • Atomic spectra are mostly in UV (sometime in visible) regions دیپارتمنت کیمیای فارمسی وکنترول ادویه
Absorption Spectroscopy • Introduction • A.) Absorption: electromagnetic (light) energy is transferred to atoms, ions, or molecules in the sample. Results in a transition to a higher energy state. • Transition can be change in electronic levels, vibrations, rotations, translation, etc. • Concentrate on Molecular Spectrum in UV/Vis (electronic transition) • Power (P): energy of a beam that reaches a given area per second • Intensity (I): power per unit solid angle • P and I related to amplitude2 (excited state) Energy required of photon to give this transition: hn =DE= E1 - Eo (ground state) دیپارتمنت کیمیای فارمسی وکنترول ادویه
B.) Terms: • 1.) Beer’s Law: A = ebc • The amount of light absorbed (A) by a sample is dependent on the path length (b), concentration of the sample (c) and a proportionality constant (e – molar absorptivity) • Amount of light absorbed is dependent on frequency (l) c Increasing Fe+2concentration دیپارتمنت کیمیای فارمسی وکنترول ادویه Absorbance is directly proportional to concentration Fe+2
B.) Terms: • 1.) Beer’s Law: A = ebc • Transmittance (T) = P/Po %Transmittance = %T = 100T • Absorbance (A) = log10 Po/P No light absorbed- % transmittance is 100% absorbance is 0 All light absorbed- % transmittance is 0% absorbance is infinite دیپارتمنت کیمیای فارمسی وکنترول ادویه
Relationship Described in Terms of Beer’s Law • A = Absorbance = ebc = -log(%T/100) • e = molar absorptivity: constant for a compound at a given frequency (l) • units of L mol-1 cm-1 • b = path length: cell distance in cm • c = concentration: sample concentration in moles per liter. • Therefore, by measuring absorbance or percent transmittance at a given frequency can get information related to the amount of sample (c) present with an identified e and l. Note: law does not hold at high concentrations, when A > 1 دیپارتمنت کیمیای فارمسی وکنترول ادویه
Molar Absorptivity A = lc is a measure of the amount of light absorbed per unit concentration at a particular . Molar absorptivity is a constant for a particular substance, so if the concentration of the solution is halved, so is the absorbance at sufficiently dilute concentrations. A concentration دیپارتمنت کیمیای فارمسی وکنترول ادویه
Cuvettes (sample holder) • Polystyrene • 340-800 nm • Methacrylate • 280-800 nm • Glass • 350-1000 nm • Suprasil Quartz • 160-2500 nm دیپارتمنت کیمیای فارمسی وکنترول ادویه
