Methods of Chemical Analysis

Selecting an Analytical Technique  Organic vs. Inorganic materials  Organic:  Inorganic:  Quantitative vs. Qualitative determination  Must identify first then determine amount

Chromatography  A means for separating and identifying organic mixtures into their component parts by using their attraction to a ________________ while being propelled through a _________________

Types of Chromatography 1._____________________ : Used to identify inks and other dyes. The molecules will travel at different speeds as they are pulled along paper (stationary phase) by a solvent (mobile phase). Thus separating the mixture.  aper.htm#description aper.htm#description aper.htm#description

Paper Chromatography

2. Gas Chromatography (GC)  Separates mixtures on the basis of their distribution between a stationary liquid phase and a moving gas phase.  Can separate highly complex mixtures within minutes  Carrier Gas: moving phase  Packed or Capillary Column: Heated thin layer of liquid contained within column

Gas Chromatography

Gas Chromatography cont… Pyrolysis GC :  Pyrolysis:  Pyrogram:

3. High Performance Liquid Chromatography (HPLC)  Moving phase is a liquid that is pumped over chemically treated solid particles (stationary phase). The liquid carries the sample over the particles and they “stick” to particles at different spots  Performed at room temp  Used for

HPLC

HPLC

HPLC

4. Thin Layer Chromatography (TLC)  Thin Layer Plate:  Sample will separate out as moves up gel plate

TLC Chromatogram

5. Electrophoresis  Separation of molecules through their migration on a gel medium  Materials are pulled through by electric charge of sample  Used for characterization of

Electrophoresis

Electrophoresis

Electrophoresis

Spectrophotometry  Analytical method for identifying a substance by  Instrument used to measure and record absorption spectrum of a chemical substance  Relates to the amount of substance  Variety of types:

Mass Spectrometer Mass Spec: Identifies and Measures the amount of substance found in a sample  Computer Attached: records, stores and compares large amounts of data with a mass spectra library  Important for analyzing:  Samples must be pure  So what do you do first?

Mass Spectrometer

Mass Spectrometry

Mass Spec

Inorganic Analysis  Important Instrumentation for determining the components of:  Example: Kennedy Assassination  The analysis of the bullet contents leads to some puzzling questions  Atomic Absorption Spectrophotometer: -Detects trace elements -Also useful for establishing the source of materials in evidence

Absorption & Emission Spectra

Neutron Activation Analysis Provides a nondestructive method of identifying and quantifying trace elements most sensitive method for quantifying  Involves  Can simultaneously analyze elements  Extremely expensive – sophisticated method needs a lot of training (can you guess why?)  Used for analyzing

Neutron Activation

X- Ray Diffraction  Aiming a beam of X-rays at crystals reveals a diffraction pattern.  Every compound produces its own unique pattern  Used for

Comparison of X- Ray Diffraction Patterns

Ugh…. Glad that one is over. Do you think they are?