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Pharmacy 325

Pharmacy 325. Infrared (IR) Spectroscopy Dr. David Wishart Rm. 2123 Ph. 492-0383 david.wishart@ualberta.ca Hours: anytime after 4 pm. Lecture Notes Available At:. http://redpoll.pharmacy.ualberta.ca http://www.pharmacy.ualberta.ca/pharm325/. Electromagnetic Spectrum.

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Pharmacy 325

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  1. Pharmacy 325 Infrared (IR) Spectroscopy Dr. David Wishart Rm. 2123 Ph. 492-0383 david.wishart@ualberta.ca Hours: anytime after 4 pm

  2. Lecture Notes Available At: • http://redpoll.pharmacy.ualberta.ca • http://www.pharmacy.ualberta.ca/pharm325/

  3. Electromagnetic Spectrum

  4. Electromagnetic Spectrum Hz 1021 1018 1015 1012 109 106 l (nm) 10-3 1 200 500 106 109 1012 Visible X-ray Ultraviolet Cosmic Radio Microwave Infrared

  5. Different Types of IR • Near Infrared • 1-3 m (wavelength) used in particle and composition analysis • Middle Infrared • 3-50 m (wavelength) primarily used in compound characterization • Far Infrared • 50-1000 m (wavelength) not used

  6. IR in Everyday Life Thermal Imaging (Thermography)

  7. IR in Everyday Life Night Vision Goggles

  8. IR Spectroscopy aspirin

  9. Principles of IR • Measures heat or thermal energy in a molecule or a system • IR spectroscopy measures the absorption of light due to bond stretching or bending • IR energies correspond to the energies of bond stretching in most molecules • Different types of bonds absorb at different energies (frequencies)

  10. Principles of IR hn Low Energy High Energy

  11. Different Types of Vibration Symmetric Stretch Asymmetric Stretch Wagging

  12. Different Types of Vibration Rocking Twisting Scissoring

  13. The IR Equation m2 hn = k(m1 + m2) m1 m2 k m1 nobsO-H > N-H > C-H > C-O > C-C > C-F nobsC=C > C=C > C-C

  14. IR Characteristic Vibrations

  15. IR Units of Measurement • Energies ~ 1-10 kcal/mol or 0.1 - 1.0 eV • Wavelength ~ 1000 nm - 100,000 nm • Frequency ~ 10 - 10 Hz • Wave number (1/l) ~ 200 - 4000 cm-1 12 15 n = c/l Frequency is proportional to wave number

  16. UV vs. IR • IR has narrower peaks relative to UV • IR yields more information than UV • IR allows you to collect data on solids, liquids and gases • UV is more quantitative than IR • UV spectra are easier/faster to collect • UV samples are easier to prepare • UV spectrometers are cheaper

  17. IR vs. UV Absorbance 230 240 250 260 270 280 290

  18. A Modern FTIR instrument FT = Fourier Transfrom

  19. FTIR Schematic 50% beamsplitter fixed mirror path “b” moving mirror path “a” a b x j- stop detector sample source

  20. for = m, get constructive interference  = 0  is “retardation” =/2 for = (m+1/2), get destructive interference

  21. Interferogram: x = 0 x = 0 Mirror travel FT Single beam spectrum of air: 100% H2O CO2 H2O 400 4000 Frequency, (cm-1)

  22. Fourier Transformation iwt F(w) = f(t)e dt Converts from units of time to units of frequency

  23. Principles of FTIR

  24. IR Sample Preparation • Most flexible system for analyzing all 3 states of matter (solid, liquid, gas) • “Neat” (analysis of liquids/oils) • Pellet (analysis of solids) • Thin Cell (analysis of dissolved solid samples - solutions) • Long Cell (analysis of gases)

  25. Preparing a “Neat” IR Sample

  26. Preparing a KBr Disk

  27. Apparatus for KBr Disk

  28. Pressed Disk Preparation • Use powdered, dry KBr, KI, CsI • Mix reagent with KBr in 1:10 ratio • Grind material to 2 m diameter using agate mortar or vibrating ball mill (Wig-L-Bug amalgamator) • Place into die and press to 30 tons/in2 using hand press or wrench + nut • Remove carefully, handle with gloves

  29. IR Liquid Sample Cell

  30. IR Gas Sample “Cell”

  31. Analyzing IR Spectra • Look for C=O peak (1820-1660 cm-1) • If C=O check for OH (3400-2400 cm-1) • indicates carboxylic acid • If C=O check for NH (3500 cm-1) • indicates amide • If C=O check for C-O (1300-1000 cm-1) • indicates ester • If no OH, NH or C-O then ketone

  32. Analyzing IR Spectra • If no C=O check for OH (3600-3300 cm-1) • indicates alcohol • If no C=O check for NH (3500 cm-1) • indicates amine • If no C=O & no OH check C-O (1300 cm-1) • indicates ether • Look for C=C (1650-1450 cm-1) then aromatic

  33. IR Characteristic Vibrations

  34. Sample IR Spectrum #1 A - CO-OH stretch (3000) B - CH stretch (2800) C - C=O ester (1757) D - C=O carboxy (1690) E - C=C aromatic (1608) F - C=C aromatic (1460)

  35. O C CH3 Sample IR Spectrum #2 C B A Acetophenone A) C=O (1730) B) C=C aromatic (1590) C) C-H aromatic (3050)

  36. Applications • Qualitative “fingerprint” check for identification of drugs • Used for screening compounds and rapid identification of C=O groups • Can be used to characterize samples in solid states (creams and tablets) • Can detect different crystal isoforms (polymorphs) • Water content measurement

  37. Applications • Analysis of urine and other biofluids (urea, creatinine, protein)

  38. Applications • Used in non-invasive measurement of glucose

  39. Applications of Near IR (NIR) • Quality control of pharmaceutical formulations • Determination of particle size • Determination of blend uniformity • Determination or identification of polymorphic drugs

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