Lecture 3512/2/05

Mobile phase

• Volume flow rate• mL solvent/minute travle

• Linear flow rate• cm of column length/min

'1r

'2r

mr'r

t

t αetention: relative r

ttime: tetention tadjusted r

Vr = retention volume = volume of mobile phase needed to elute specific compound

m

s

mm

ss'

'

m

'r

m

mr'

V

VK

VC

VCk

phase mobile in solute of olesm

phase stationary in solute of olesm

phase mobile in spends solute time

phase stationary in spends solute time k

t

t

t

ttactor: kCapacity f

1

2'1

'2

'1r

'2r

K

K

k

k

t

tα

What does a good chromatogram look like?

av21

r

av

r

av

r

w

Δt549.0

w

Δt

w

ΔtsolutionRe

Resolution: Degree of separation between peaks

Band broadening caused by diffusion

Dtσ 2

Broadening before and after column

• Variance is additive

12

)t(σσ

22

ectordet2injection

Column efficiency

• Quantitative measure of band broadening

• Plate height and number of plates

Plate Height

xx

2

Cuu

BAH

time ionequilibrat diffusion paths multipleHx

σH

x = distance traveled

van Deemter equation

Open tubular columns = 0