Chapter 5 and 6 Organic and Inorganic Chemical Analysis

1. Chapter 5 and 6 Organic and Inorganic Chemical Analysis

2. Phase Changes: (physical state changes) • Melting: from solid directly into liquid • Freezing: from liquid directly into solid • Vaporization: from liquid directly into gas • Condensation:from gas directly into liquid • Sublimation:from solid directly into gas • Deposition:from gas directly intosolid

3. Phase Diagrams:

4. Matter Can be separated by physical methods No Yes Pure Substance Uniform Composition? Can it be broken down further ? Yes No Yes No Compound Element Homogeneous (solution) Heterogeneous Mixture

5. Selecting an Analytical Technique • Organic: a substance composed of carbon(often contain hydrogen and smaller amounts of oxygen, nitrogen, chlorine, or phosphorus) • Inorganic:a chemical compound not based on carbon

6. Questions to consider in choosing ananalytical (chemical) method: • Quantitative or qualitative required • Sample size and sample preparationrequirements • What level of analysis is required (ex. ± 1.0% or ± 0.001%) • Detection levels • Destructive or non-destructive • Availability of instrumentation • Admissibility

7. What Is Chromatography? • Laboratory technique 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

8. Chromatography Review • Chromatographic systems have a stationary phaseand a mobile phase (usually liquid or gas) • The mixture to be separated is placed on the stationary phase • The mobile phase then “pushes” the components of the mixture through the system • Each component adsorbs on the stationary phase with a different strength (stronger means moves more slowly through the system) • Each component comes out the end of the system at a different time (retention time) • When the molecules reach the far end of the surface, they are detected or measured one at a time as they emerge

10. Chromatography is non-destructive • Separation of components depends on both their solubility in the mobile phase and their differential affinity to the stationary phase.

11. Street Drugs in Real Time Amphetamine Methamphetamine and MDMA Hydrocodone Cocaine Oxycodone

12. Types of Chromatography • Paper Chromatography • Thin-Layer Chromatography (TLC) • Liquid Chromatography (HPLC) • Gas Chromatography (GC)

13. 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 • Components appear as separate spots spread out on the paper after drying

14. Thin Layer Chromatography (TLC) • Stationary Phase • a thin layer of adsorbent coating on a sheet of plastic or glass • Mobile Phase • a liquid solvent • Sample mixture spotted onto the adsorbent • - Solids must first be dissolved • - Liquids can be directly applied • Some components bind to the adsorbent strongly; some weakly • Components appear as separate spots after development

15. TLC

16. Retention Factor (Rf) • An indication of how far a compound travels in a particular solvent • Good gauge of whether an unknown and a known compound are similar • Rf= distance the solute (D1) moves divided by the distance traveled by the solvent front (D2) • Rf= D1 • D2

17. Gas Chromatography • Stationary phase • a solid or very “syrupy” liquid in a tube (column) • Mobile phase • an inert gas (carrier gas) • Usually nitrogen or helium

18. Analysis Using the GC • Retention time can be used as an identifying characteristic of a substance • retention times may not be unique • An extremely sensitive technique • area under a peak is proportional to the quantity of substance present • allows quantitation of sample • Retention time: time between when the sample is injected and when it exits the column reaching the detector

19. Retention Time Tmis the time it takes for the mobile phase to pass through the column

21. High Performance Liquid Chromatography (HPLC) • Stationary phase • fine solid particles which are chemically treated • Mobile phase • a liquid • Advantage: takes place at room temperature • Used for organic explosives that are heat sensitive as well as heat sensitive drugs

22. Mass Scale Atomic and Molecular Weights • Atomic Mass Scale - based upon 12C isotope. This isotope is assigned a mass of exactly 12 atomic mass units (amu) and the masses of all other atoms are given relative to this standard. • Most elements in nature exist as mixtures of isotopes (atoms of an element that have different numbers of neutrons but same number of protons).

23. Mass Spectrometry (MS or mass spec) Basic Ideas Creates charged particles (ions) from gas phase molecules. The Mass Spec analyzes ions to provide information about the molecular weight of the compound and its chemical structure.

24. Mass Spectrometer (MS) • As the sample leaves the GC or HPLC, it enters the Mass spec. • Within the MS, a beam of electrons is shot at the substance breaking it down into fragments • These fragments pass through an electric field which separates them by their masses • The fragment masses are then recorded • Each substance breaks down into its own characteristic pattern

25. Mass Spectrometer Atomic Spectra Mass Spectrum Mass Spectrum Mass Spectrum Int. Int. Int. P Cl C 35 31 12 37 13 mass number (amu) mass number (amu) mass number (amu) 31P: 100% abundant 35Cl: 75% abundant 37Cl: 24% abundant 12Cl: 98.9% abundant 13Cl: 1.11% abundant

26. The unique feature of mass spectrometry is that under carefully controlled conditions, no two substances produce the same fragmentation pattern • Allows for identifying chemical substance • Each mass spectrum is unique to each drug and so serves as specific test for identifying the substance

27. Mass Spectrometer Unknown white powdery substance ingested by unconscious patient. What do you do? Is it Heroin, Cocaine, Caffeine? Mass Spectrum of Unknown Compound

28. Mass Spectrometer MS Library Heroin MS of Unknown

29. Mass Spectrometer Cocaine MS Library MS of Unknown

30. Mass Spectrometer MS Library Caffeine MS of Unknown

31. Mass Spectrometer Unknown white powdery substance ingested by unconscious patient. What do you do? Mol. Wgt = 194 Mass Spectrum Caffeine

32. Electrophoresis • Separates materials based on their migration rates on a stationary solid phase • Passes an electrical current through the medium and allows for classification of proteins (DNA)

34. Most useful applications ofElectrophoresis • Characterization of proteins and DNA in dried blood • Proteins migrate at speeds that vary according to their electrical charge and size resulting in characteristic band patterns

35. Spectroscopy and Spectrophotometry • Study of absorption of light by chemical substances • Used for identification of various organic materials or for presence of trace elements • Electromagnetic spectrum – entire range of “light waves” • Colors – absorption or reflection of various wavelengths of visible light • Ultraviolet or infrared radiation (either side of visible region) • X-ray – high energy, short wavelength

36. Incoherent light – light comprised of waves that are out of step with each other

37. Coherent or laser light – light whose waves are pulsating in unison • Laser (light amplification by the simulated emission of radiation)

38. Photon – small packet of electromagnetic radiation energy. • Each photon contains a unit of energy • E = hν • E = energy of photon • ν= frequency of radiation • h = Plank’s constant (6.626 X 10-34 J•s)

39. The Spectrophotometer • Instrument used to measure and record the absorption spectrum of a chemical substance

40. UV Spectrophotometry • Measuresabsorbance of UV and visible light as a function of wavelength or frequency • Allows tentative identification • Ex. White powder with UV spectrum comparable to that of heroin results in a tentative identification

41. UV Spectrum

42. Infrared Spectrophotometry • Different materials always have distinctively different infrared spectra • Each IR spectrum is therefore equivalent to a “fingerprint” of that substance and no other • Extensive catalogue of IR spectra of organic compounds allows for identification of organic substances

43. IR Spectrum

44. Atomic Emission Spectroscopy (AES) • Used to detect the types of elements present in a sample • Can use measurement of the emissions from excited atoms to determine concentration. • Frequency of light given off The Hydrogen Discharge Tube • H2molecules are excited by an electric discharge • As the atoms return to lower energy states, light is emitted

46. Flame Tests Atomic Emission

48. Atomic Absorption Spectroscopy (AAS) • Sample heated and atoms absorb radiation • Atoms become excited • The amount of radiation absorbed is recorded • Can be used to quantitate amounts based on a calibration curve • Beer’s Law (Absorption is proportional to concentration)

49. Example: • Determination of the wavelength of lightabsorbed by a sample of grape soda Absorption of Grape Soda

50. Example: • Determination of the amount of dilution of a sample of grape soda