Ch 5 - Organic Analysis

1. Ch 5 - Organic Analysis Elements and compounds. Solids, liquids, and gases. Phase Organic vs inorganic compounds. Qualitative vs quantitative analysis. Henry’s law and equilibrium state. Chromatography. Retention time.

2. Thin-layer vs gas chromatography. Rf value. Electrophoresis. Theories of light: wave vs particle. Electromagnetic spectrum. Relationship between color and absorption of light by molecules. Beer’s law. Absorption spectrophotometer. Ultraviolet (UV) and Infrared (IR) spectrum for identification of organic compounds.

3. Mass Spectrometry (MS) Significance of mass spectrum in forensic science.

4. Matter: all things of substance. Matter is composed of atoms or molecules.   Element: a fundamental particle of matter. An element cannot be broken down into simpler substances by chemical means.  Periodic table: chart of elements arranged in a systematic fashion. Vertical rows are called groups or families; horizontal rows are called series. Elements in a given row have similar properties. Compound: a pure substance composed of two or more elements

5. Physical state: a condition or stage in the physical being of matter; a solid, liquid, or gas   Solid: a state of matter in which the molecules are held closely together in a rigid state  Liquid: a state of matter in which molecules are in contact with one another but are not rigidly held in place  Gas (Vapor): a state of matter in which the attractive forces between molecules are small enough to permit them to move with complete freedom  Sublimation: a physical change from the solid directly into the gaseous state

6. Phase: a uniform piece of matter; different phases are separated by definite visible boundaries  Organic: a substance composed of carbon and hydrogen, and, often, smaller amounts of oxygen, nitrogen, chlorine, phosphorus, or other elements  Inorganic: a chemical compound not based on carbon  Spectrophotometry: an analytical method for identifying a substance by its selective absorption of different wavelengths of light  

7. Chromatography: any of several analytical techniques whereby organic mixtures are separated into their components by their attraction to a stationary phase while being propelled by a moving phase  Pyrolysis: the decomposition of organic matter by heat  Fluoresce: to emit visible light when exposed to light of a shorter wavelength-i.e., ultraviolet light  

8. Electrophoresis: a technique for the separation of molecules through their migration on a support medium while under the influence of an electrical potential  Proteins: polymers of amino acids that play basic roles in the structures and functions of living things  Enzyme: a type of protein that acts as a catalyst for certain specific reactions  Visible light: colored light ranging from red to violet in the electromagnetic spectrum

9. Wavelength: the distance between crests of adjacent waves   Frequency: the number of waves that pass a given point per second  Electromagnetic spectrum: the entire range of radiation energy from the most energetic cosmic rays to the least energetic radio waves  X-ray: a high energy, short wavelength form of electromagnetic radiation

10. Laser: light amplification by the simulated emission of radiation. Light that has all its waves pulsating in unison  Photon: a small pocket of electromagnetic radiation energy. Each photon contains a unit of energy equal to the product of Planck’s constant and the frequency of radiation: E= hf  Monochromator: a device for isolating individual wavelengths or frequencies of light  Monochromatic light: light having a single wavelength or frequency

11. Ultraviolet: Invisible long frequencies of light beyond violet in the visible spectrum   Infrared: invisible short frequencies of light before red in the visible spectrum  Ion: an atom or molecule bearing a positive or negative charge

12. Gas Chromatograph (GC)

13. Thin-Layer Chromatography (TLC)

14. Electrophoresis

15. Electromagnetic Spectrum

17. UV-VIS Spectrophotometer

18. UV-VIS Spectrum

19. IR Spectrophotometer

20. IR Spectrum

21. Mass Spectrometer (MS)

22. Mass Spectrometer

23. Mass Spectrum

24. Ch.5 Organic Analysis Chromatography

28. Chromatography Separation of Mixtures

29. What Is Chromatography? A family of laboratory techniques for separating mixtures into their component compounds Uses some version of a technique in which two phases, one mobile, one stationary, flow past one another The mixture separates as it interacts with the two phases

30. Basic Principle Different compounds will stick to a solid surface with different degrees of strength or vary in the efficiency with which they dissolve in a liquid

32. Basic Principles A mobile phase sweeps the sample over a stationary phase like the wind sweeps the swarm over the flower bed

33. Basic Principles When a mixture of compounds flows over a surface, the molecules will stick to the surface If a molecule does not stick to the surface too strongly, the molecule stick & unstick many times as it is swept along the surface Over time, the molecules will become physically separated from each other

35. Basic Principles When the molecules reach the far end of the surface, they are detected or measured one at a time as they emerge Chromatography is non-destructive does not alter the molecular structure of the compounds

38. Types of Chromatographic Attraction Adsorption Chromatography depends on physical forces such as dipole attraction to cause the molecules to “stick” to the stationary phase column, TLC, HPLC

39. Types of Chromatographic Attraction Partition Chromatography depends on the relative solubility of the mixture’s molecules in the stationary phase coating polarity may also have some effect gas chromatography

40. Types of Chromatographic Attraction Size-exclusion the relative sizes of the molecules determine how fast the molecules move through the stationary phase large molecules flow right through small molecules spend time trapped in the pores of the stationary phase gel filtration chromatography

41. Types of Chromatographic Attraction Ion-exchange depends on the relative strength with which ions interact with an ionic resin less strongly held ions are displaced by more strongly attaching ions one kind of ion is exchanged for another ion exchange chromatography

42. Paper Chromatography Stationary phase a sheet or strip of paper mobile phase a liquid solvent Sample mixture spotted onto the paper Capillary action moves mobile phase through stationary phase

43. Paper Chromatography Components appear as separate spots spread out on the paper after drying Can be used for ink analysis

44. Paper Chromatography 2D Chromatography accomplished by running another chromatography with the paper turned 90o Can complete separation of overlapping compounds

45. Thin Layer Chromatography Stationary Phase a thin layer of adsorbent coating on a sheet of plastic or glass usually Al2O3 (alumina) or SiO2 (silica) Mobile Phase a liquid solvent Sample mixture spotted onto the adsorbent

46. TLC Some components bind to the adsorbent strongly; some weakly Components appear as separate spots after development

47. Retention Factor (Rf) quantitative indication of how far a compound travels in a particular solvent good indicator of whether an unknown & a known compound are similar, if not identical If the Rf value for the unknown compound is close to or the same as that for the known compound, the two compounds are most likely similar or identical

48. Retention Factor (Rf) Rf = distance the solute (D1) moves divided by the distance traveled by the solvent front (D2) Rf = D1 / D2 Rf <1.0

49. Gas Chromatography Stationary phase a solid or very syrupy liquid lines a tube (column) silicone polymers (like Silly Putty) commonly used Mobile phase an inert gas nitrogen helium

52. GC Columns

54. Schematic of a GC

55. Retention Time

56. Retention Time The time between when the sample is injected & when it exits the column reaching the detector Tm is the time taken for the mobile phase to pass through the column

57. Analysis Using the GC Retention time can be used as an identifying characteristic of a substance retention times may not be unique GC is not an absolute method of identification An extremely sensitive technique area under a peak is proportional to the quantity of substance present allows quantitation of sample

58. Identification of Accelerants

59. Pyrolysis Gas Chromatography Used when sample does not readily dissolve in a solvent If heating such sample at high temp (500-10000C) decomposes it into gaseous products, the products can be analyzed by CGC A pyrogram is obtained

60. High Pressure Liquid Chromatography (HPLC) Stationary Phase fine solid particles Mobile Phase a liquid solvent The solvent is pumped through the column The sample components are retarded by different amounts by interaction with the column packing

61. Schematic of HPLC

64. Advantages of HPLC Separation occurs at room temperature Does not decompose heat sensitive materials explosives heat sensitive drugs like LSD

65. Analysis of Components of Sake Sake is composed of several chemical components sugar organic acids amino acids Each component relates to the taste of the sake

68. Spectroscopy Compound Identification

69. Wave Nature of Light Wavelength distance between crests Frequency number of crest that pass a given point in one second

70. Wave Nature of Light Energy frequency & energy are proportional

71. The Electromagnetic Spectrum

72. The Hydrogen Atom The electron structure of an atom is quantized electrons can only exist in discrete energy levels

73. Excitation When a “packet” of energy equal to the energy difference between two energy levels is absorbed electron is promoted

74. Excitation

75. Deexcitation As the electrons falls back to the ground state an energy “packet” is emitted

76. Deexcitation

77. Visible Spectroscopy

78. Visible Spectroscopy

79. Beer’s Law

80. Example Determination of the wavelength of light absorbed by a sample of grape soda Determination of the amount of dilution of a sample of grape soda

81. Absorption of Grape Soda

82. Dilution of Grape Soda

83. UV-VIS Spectrophotometry Can give information about the structure of the compound (qualitative info) positions of the absorption maxima Can quantitate the sample Beer’s Law analysis

84. Electromagnetic Radiations Each type of electromagnetic radiation is composed of wavelengths possessing a range of energies related to the frequency of the wave Each type of electromagnetic radiation will cause different types of excitation in a sample of matter dependent on the amount of energy the wave possesses

87. IR Radiation Exposing molecules to the correct frequencies of infra-red light will result in some of that light being absorbed gives that molecule more energy results in more energetic motion of the atoms in the molecule

88. IR Probes different molecular vibrations absorption occurs when the frequency of the IR wave matches a vibrational frequency of the molecule Most molecules have numerous vibrations bond stretching vibrations detect different kinds of A-B bonds bond bending involves several atoms at once

89. Molecular Motions

90. Cocaine

93. The Mass Spectrometer A detector Allows the identification of a chemical compound In the MS, a compound is bombarded with a stream of electrons compound breaks into fragments each compound gives a unique set of fragments “fingerprint”

95. GC/MS As individual compounds elute from the GC column, they enter the MS detector Fragmented by electron bombardment fragments are charged ions with a certain mass mass to charge ratio (M/Z) Z is usually +1 M/Z represents that molecular weight of the fragment