Chromatographic Theory - UMass

CEE 772 Lecture #13

10/23/2014

Updated: 23 October 2014

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CEE 772:

Instrumental Methods in

Environmental Analysis

Lecture #13

Gas Chromatography: Basic Chromatographic

Theory

(Skoog, Chapt. 26, pp.674©\696)

(Harris, Chapt. 238)

(646-667)

David Reckhow

CEE 772 #13

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Chromatographic Theory

? References:

¨C Skoog, Principles of Instrumental Analysis

? 1985 (3rd ed): parts of Chapter 25

? 1991 (4th ed): parts of Chapter 25

? 1998 (5th ed): parts of Chapter 26

David Reckhow

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CEE 772 Lecture #13

10/23/2014

Chromatography basics

? The basis for gas chromatography is the distribution

of a sample between 2 phases, namely a stationary

phase and a gas phase

? Gas Chromatography

¨C A technique for separating volatile substances by

partitioning between the vapor phase and a dissolved or

solid phase

? Gas©\Liquid Chromatography ©\©\©\©\©\ Stationary phase is a liquid.

? Gas©\Solid Chromatography ©\©\©\©\©\©\ Stationary phase is a solid.

David Reckhow

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Components of a Chromatographic System

? Source of Carrier Flow (mobile phase)

¨C Cylinder of carrier gas or solvent bottles

?

?

?

?

Injection port (sample inlet)

Column with stationary phase

Detector(s)

Signal Transducers & Data Analyzers

¨C Recorders, integrators

¨C Computers for library matching

? Controllers

¨C Temperature controls for injectors, columns and detector

¨C Flow controllers and pressure regulators

David Reckhow

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CEE 772 Lecture #13

10/23/2014

A Gas Chromatograph

Three Heated Zones

Injector

Detector

Carrier

Gas

Column Oven

Data System

Gas Chromatograph

David Reckhow

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David Reckhow

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CEE 772 Lecture #13

10/23/2014

The Column

Gas Chromatograph

Fused Silica

Open Tubular Column

Stationary Phase

A

A

Gas

Flow

Column Wall

Mobile Phase

B

B

David Reckhow

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David Reckhow

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CEE 772 Lecture #13

10/23/2014

mobile phase

sample

A+B

B

A

B

A

B

A

t1

t2

David Reckhow

t3

B

t4

t5

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LLE & Chromatography

Solvent Extraction:

Organic

phase

Aorg

Aqueous

phase

Aaq

Aaq

Aorg K =

Am

As

[A]org

[A]aq

Chromatography:

Mobile

phase

Am

Stationary

phase

As

David Reckhow

K=

A = Analyte

C = Concentration of analyte

m = mobile phase

sCEE

= 772

stationary

phase

#13

Cs

Cm

10

5

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