Chromatography Chromatography means of separating and tentatively identifying

Chromatography • Chromatography – means of separating and tentatively identifying the components of a mixture. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -1

Chromatography • Molecules that have a preference for the moving phase will slowly pull ahead and separate from those substances that prefer to remain in the stationary phase. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -2

An analogy FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -3

Paper Chromatography FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -4

Rf Values FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -5

• Calculate the Rf value for each spot FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -6

TLC • TLC uses a solid stationary phase usually coated onto a glass plate and a mobile liquid phase to separate the components of the mixture. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -7

TLC • The liquid will slowly rise up the plate by capillary action – the sample to become distributed between the stationary phase and the moving liquid phase. • Most compounds are colorless – materials must be visualized by placing the plates under ultraviolet light or spraying the plate with a chemical reagent. • Rf values calculated. FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -8

Gas Chromatography • Research gas chromatography. Create a brochure individually that answers the following questions. – What is gas chromatography (GC)? – How does GC work? (Find a visual to help illustrate this) Describe using a few sentences. – What does a gas chromatograph set up look like? What are the parts? Find or draw a visual and label! – What is the written record or data from a GC look like? What is it called? Find an example and print it. – Why/how is GC used in Forensic Science? FORENSIC SCIENCE: An Introduction, 2 nd ed. By Richard Saferstein © 2011, 2008 Pearson Education, Inc. Upper Saddle River, NJ 07458 5 -9