Lecture 16:Thin Layer Chromatography

CU- Boulder CHEM 5181

Mass Spectrometry & Chromatography

Prof. Jose-Luis JimenezFall 2002

Schematic of TLCArrangement

2

⎟⎠⎞

⎜⎝⎛=σ

RtN

2

16 ⎟⎟⎠

⎞⎜⎜⎝

⎛=

W

A

ddN

TLC:

Column C:

Example of TLC

Introduction to TLC

• Applications– Screening many samples very quickly– Analysis in cases where sample preparation is

very difficult– Analysis of compounds in complex matrices

• Time per analysis: 3-15 min.• Limitations

– Non-volatile compounds– Low separating power

Comparison to HPLC• HPLC

– “Serial” process: all analytes go through the same column, detector

• Possibility of “carryover”– Detection in the presence of mobile phase

• TLC– “Parallel” process: many samples analyzed

simultaneously, side-by side– SP is used only once

• “Carryover” is not a problem– Off-line: Analytes are “stored” on plate

• Measurements can be done repeatedly

Two-Dimensional TLC

HPTLC

• Characteristics– Smaller particles (6 mm instead of 12-20)– Thinner Layers (100 mm instead of 250)– Narrow particle size distribution– Why?

• Advantages– Faster– Cheaper (smaller plates)– Improved detection limits

Common TLC Stationary Phases

Adsorbents for TLC