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. Thin-layer vs gas chromatography. Rf value. Electrophoresis.
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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.
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.
Mass Spectrometry (MS) • Significance of mass spectrum in forensic science.
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
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
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
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
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
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
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
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
Ch.5 Organic Analysis Chromatography
Chromatography Separation of Mixtures
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
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
Basic Principles • A mobile phase sweeps the sample over a stationary phase • like the wind sweeps the swarm over the flower bed
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
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
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
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
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
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
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
Paper Chromatography • Components appear as separate spots spread out on the paper after drying • Can be used for ink analysis
Paper Chromatography • 2D Chromatography • accomplished by running another chromatography with the paper turned 90o • Can complete separation of overlapping compounds
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
TLC • Some components bind to the adsorbent strongly; some weakly • Components appear as separate spots after development
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
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
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