chapter 8 liquid chromatograph

LOGOChapter 8 Liquid Chromatograph Chapter 8 Liquid Chromatograph

8.1 Introduction

High pressures

High speed

High performance

High sensitivity

LOGO8.2 Principles8.2 Principles

Adsorption process

Xm + n Sa Xa + n Sm

(1)Liquid – Solid chromatography

nam

nma

SX

SXK

1.Classification

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(2) Liquid – Liquid Chromatography

Partition Process

Xm Xs

kKm

s

s

m

v

v

C

C

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(3) Ion Exchange Chromatography

X+ + Y(resins) Y+ + X(resins)

resinYX

YresinX

m

m

K

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(4) Ion pair Chromatography

aa

K-

O-

YX

YX

X+a + Y-

a X+ Y-

org

LOGO2. Column efficiency of LLC2. Column efficiency of LLC

smmsdl HHHHHH

pl dH 2Eddy diffusion

u

DCH md

d

Longitudinal diffusion

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uD

dCH

uD

dCH

uD

dCH

m

psmsm

m

pmm

s

fss

2

2

2

Mass transfer

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22

2

pm

sm

m

mf

s

s

md

p

dD

C

D

Cd

D

CC

DCB

dA

Cuu

BAH

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H-U curve of GC and LC

LOGO3. Separation of Components3. Separation of Components

(1)Resolution R

)(5.0 21

1,2,

YY

ttR RR

(2)Separation Factor

1

2

1

2

1

2

1

2

'

'

'

'

V

V

t

t

k

k

K

K

7-19

7-20

LOGO4. Separation Equation of LC4. Separation Equation of LC

Assume: Y1=Y2=Y, k1≈k2=k

212

1216 k

kRn

2

1216

Rneffect

11

41

k

knR

7-21

7-22

8-23

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5. Factors affect Resolution of a column

(1) Plat number n = f ( L,H )

H=f (u,k,Dm,Ds, ….)

(3) Selectivity factor α= k2 / k1

(2) capacity factor k= p/q

P,q relay to mobile & stationary phase

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mm uLt /

kkttkttuL

mRmR '),1(

,...),,,(,)1( mk

nk DkHLf

4,1 Yh

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8.3 Instrumentation of LLC

1. LLS System

(1) Reservoirs (2) Pump

(3) Sample Injection Port

(4) Column (5) Detector

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2. stationary phase

3. mobile phase (solvent)

Porous micro beads support

Pellicular micro beads support

Polarity order

N-Heptane < … < water

LOGO4. Gradient elution

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5. Detector