Chemical AnalysisPART 1: QUALITATIVE ANALYSIS

Chemical Analysis

One of the most important aspects of forensic science

Widely used in forensic analysisDevelop latent fingerprintObtain DNA Analyze unknown substanceIdentify drugs

Drug Identification

Use screening test first:Thin-layer chromatographyColor testMicrocrystalline test

Then instrumental analysis:SpectrophotometryMass spectrometryGas chromatography

Chromatography

The physical separation of a mixture into its individual components

Analyzing multi-component samplesInks, dyes, drugs, and poisons, etc.

Examples of Chromatography

Liquid Chromatography

Thin-Layer Chromatography(TLC)

Gas Chromatography

Paper Chromatography

Thin-Layer Chromatography TLC

Solvent Front

Heroin

Quinine

Origin

Use a solid stationary phase and a moving liquid (mobile)phase to cause a separation of the components of a mixture

Detect the colorless components separated from TLC

• Exposing to UV light• Exposing to fluorescent dyes• Exposing to iodine• Spraying with a reagent

Rf (retention factor) valueThe distance traveled

by the component divided by the distance traveled by the solvent

It is usually expressed as a decimal

Identify components by comparing to known chemicals

Solvent finish 10 cm

8 cm

4 cm

Starting point

Rf1 = 8/10 = 0.8

Rf2 = 4/10 = 0.4

Paper & Thin-layer Chromatography Tutorial

https://www.youtube.com/watch?v=J8r8hN05xXk

Color Test

Initial screening for drugs

Color changes when certain chemicals present

Very simple and less expensive

http://www.aetv.com/crime-360/video/drug-reagent-test

Microcrystalline Test

More specific than color test

Specific chemical will form specific size and shape of crystal

Quick, cheap, and no isolation required Copper Sulfate X 100