1. Organic and Inorganic Chemical Analysis
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 into solid

3. Phase Diagrams:

4. Matter Pure Substance Mixture Compound Element Homogeneous
Uniform Composition?
Heterogeneous
Can be separated
by physical methods
Pure Substance
Can it be broken down further ?
Compound
Element
Yes No
Homogeneous
(solution)
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 an analytical (chemical) method:
Quantitative or qualitative required
Sample size and sample preparation requirements
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 phase and 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
Tm is 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. Atomic and Molecular Weights
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 Cl C P Atomic Spectra 35Cl: 75% abundant
Spectrum
Mass
Spectrum
Mass
Spectrum
Int.
Int.
Int. Cl C P 35 31 12 37 13
mass number (amu)
mass number (amu)
mass number (amu)
35Cl: 75% abundant
37Cl: 24% abundant
12Cl: 98.9% abundant
13Cl: 1.11% abundant
31P: 100% 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 MS
Library
Cocaine
MS of Unknown

30. Mass Spectrometer
MS Library
Caffeine
MS of Unknown

31. Mass Spectrometer Mass Spectrum Caffeine
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 of Electrophoresis
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 J•s)

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

40. UV Spectrophotometry Allows tentative identification
Measures absorbance 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
H2 molecules 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. Absorption of Grape Soda
Example:
Determination of the wavelength of light absorbed by a sample of grape soda
Absorption of Grape Soda

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

51. Neutron Activation Analysis (NAA)
Used for determining the concentrations of elements
Process:
Neutrons interact with a target nucleus to form a nucleus in an excited state.
The excited nucleus will decay immediately into a more stable configuration through emission of gamma rays
This new configuration may yields a radioactive nucleus which continues to undergo decay but at a much slower rate (depending on the unique half-life of the sample). This decay is also measured.
Allows quantitation in parts per billion but requires a nuclear reactor

53. Neutron Activation Analysis
Rate depends on half-life
Prompt gamma ray formation
measurement taken during irradiation
Delayed gamma ray formation
measurements taken after irradiation
more common
About 70% of elements have properties suitable for measurement by NAA

54. Gamma-ray Spectra
Continuation of medium & long-lived elements