Chromatography and Separation Chemistry - ACS Publications

10

Downloaded by UNIV OF MASSACHUSETTS AMHERST on June 1, 2018 | https://pubs.acs.org Publication Date: January 27, 1986 | doi: 10.1021/bk-1986-0297.ch010

Microcomputer-Assisted Retention Prediction in Reversed-Phase Liquid Chromatography Kiyokatsu Jinno and Kazuya Kawasaki School of Materials Science, Toyohashi University of Technology, Toyohashi 440, Japan

A computer-assisted system for predicting retention of aromatic compounds has been investigated in reversed-phase liquid chromatography. The basic retention descriptions have been derived from the studies on quantitative structure-retention relationships. The system was constructed on a 16-bit microcomputer and then evaluated by comparing the retention data between measured and predicted values. The excellent agreement between both values were observed on an octadecyls i l i c a stationary phase with acetonitrile and methanol aqueous mobile phase systems. This system has been modified to give us the information for optimal separation conditions in reversed-phase separation mode. The approach could also work well for any other reversed-phase stationary phases such as octyl, phenyl and ethyl silicas. Although

liquid

chromatography

has

been

widely

used

the

last

decade.

chromatography into

their

tively. sive the

as

With

(LC),

phenomena utility

efficiency

of

the

of

history

LC h a s

been

of

for

instrument

the

selection

is

ration for find

a major

condition,

their the

phase. the

s t i l l

best

analysts

respective that,

approach

is

difficult

involves

systematic

one

In

as

order the

with

the

impres-

modern

detection well

as

to

set

data

the

are

and

sepa-

about

and

i t

then

stationary

performed

purposes. An i m p r o v e d

computer

condi-

best

information articles,

high

systems,

separation

phase

their

and t i m e - c o n s u m i n g .

optimization

qualitamost

of

mobile for

and the

development

experiments

condition

liquid separated

Furthermore,

on-line

survey of

of

it during

chemistry.

i n many p u b l i s h e d

and e r r o r

separation

is

satisfactory

LC.

combination

trial

optimal very

in

readily

ago,

only

performance

operations, of

generally

purposes

most p r o m i s i n g After

problem

the

and s p e c i f i c

and m i c r o p r o c e s s o r s tions

by

years

quantitatively

analytical

handling.

However,

high

technique

catalyzed

sensitive

of

80

techniques

c a n now b e

analyzed

this

about

analytical

mixtures

i n the

columns,

discovered

development

and then

ascent

was

efficient

complex

components

The r a p i d

an

to

find

This approach

techniques

0097-6156/ 86/ 0297-0167$06.25/ 0 © 1986 American Chemical Society

Ahuja; Chromatography and Separation Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

such

as

C H R O M A T O G R A P H Y A N D SEPARATION CHEMISTRY

168 "Window useful

Diagram" It

necessitates

In

i t

is

practice,

can create

alternate

attempt

In

tion

experimental

attained

directed

At present,

theories LC.

to

describe

solute

According to this anticipated

surface and

area,

that

sed-phase

LC.

solubility parameters

been

determined

based

deal

of

effort

promising

have

method

measure

of

made,

is

to predict

based

on t h e p r e m i s e parameters

solute

as s t r u c t u r e ,

its

retention, in

such

i f

k

is

1

which t

and been

derive

is

a l .

(29).

factor

this

benzenes,

as

coef-

good

parameter

(22-28).

in

This

quanidea

i n reversed-phase exist

electronic

LC c a n

between

the

properties states

The b a s i c

of

e t c . , and concept

is

i t

defined

and t

Q

is

k

i n various

the equation

1

= ( t

r

- t

0

) / t

0

,

t h e column v o i d - t i m e Such approach has

relationships

o n t h e QSRR s t u d i e s ,

equation-1

as

of the solute.

structure-retention

contribution,

we w i l l

one w i l l

(QSRR)

be a b l e

reversed-phase

obtained,

retention

describe

p r e d i c t i o n system

p o l y c y c l i c aromatic

application

of

by

to

LC

retention

of

predicted.

benzenes,

system

of a solute time

by u s i n g

the retention

between

a

i n reversed-phase L C .

are available.

parameters

Based

such

And t h e n , c a n be

stituted

is

(1)

the retention

equations

In struct

great most

of partition

the molecular

and/or

have

a

LC as t h e

which

(QSAR)

rever-

r e t e n t i o n and

(Pi)

as q u a n t i t a t i v e

et

solutes

system

phases

in

F o r example,

relationships

shape

i t can

solute's

parameters

an important

representing

parameters

i s physicochemical

systems.

The

= f

1

a capacity

r

named

Horvâth

is

model,

equation-1: k

in

such

between

of logarithm

retention

that

reversed-phase

as

to use reversed-phase

to say, prediction of retention

the

where

correlations

et

consistent

two i m m i s c i b l e

a n d some o f t h e s e

this

reten-

spectroscopy

the retention

relationships.

i t s hydrophobicity:

physicochemical

shown

with

i n 1-octanol/water

QSAR c a n b e a p p l i e d

in

such

between

structure-activity relationships

That be

made

much

i n t r o d u c e d by Horvâth

parameters

for the determination

o f a compound

in

on those

been

ficient titative

such

understanding

of solute

driven interaction

may c o r r e l a t e exist

pre-

procedure

years,

and/or

d i s t r i b u t i o n phenomena

In p r a c t i c e ,

physicochemical

That

can be

a s one o f t h e most

its partition coefficient

i t s aqueous

disadvantage,

(6-10).

clear

t h e mechanism

theory"

physicochemical

materi-

and t h e r e -

this

recent

by chromatography

entropically

standard

optimization

During

acknowledged

major

time.

investigate

"solvophobic

i s generally

very-

available.

of solutes

o f any s o l u t e , a

i s needed.

LC b o t h

be

toxic

To overcome

retention

is

i t has one

by the authors

i n a short

to

because

condition,

retention

mechanism

i n reversed-phase (19-21)

If

approach

of interest

this

proposed

prediction.

to predict

has been

(11-18). al.

be

easily

order

This

however,

or are highly

new p o l l u t i o n p r o b l e m s .

the retention

effort

to achieve available

approach has been

at appropriate

c a n b e more of

difficult

i s retention

dicted

(1-5).

conditions;

a l l materials

may n o t b e c o m m e r c i a l l y

fore an

methods

separation

limitation. als


or "Simplex"

to get optimal

based

hydrocarbons

on t h e use o f

and physicochemical

has been

constructed

for optimization

the basic

approach

i n reversed-phase such

(PAHs)

parameters

on a 1 6 - b i t

of separation

and polar

established

con-

alkyl-

group

sub-

relationships

of these

microcomputer, conditions

to

LC f o r

will

compounds. and the be

strated.


demon-

Microcomputer-Assisted

10. JINNO A N D KAWASAKI

Retention Prediction

169

Experimental The 2

liquid

Co.,

100III

ultraviolet

set

at

210

620

(Tokyo,

(2)

C-phenyl

The

mobile

methanol water.

A l l

Prior

the

(10

test

it

was

mobile There

have

topics

in

37),

we

LC.

elution

centration All

solutes not

reproducibility

c.a.

0.5

Seto,

Japan),

C2

(10

Japan)

a

few

and

4

from

the as

or

in

many

uL/min. each

retention

solutions

hundred parts

soluble

De-

urn).

available

analyzed

(5

(3)

equilibrated with

were

cm

and p u r i f i e d

always for

12 C18

χ

FineSIL

acetonitrile

obtained

of

mm i . d .

Jasco

was

of

publications subject

the

methanol on

is

and b a s i c

of

in

per

mobile

depending

used

capacity at

each

t

are

LC. in

0

mobile

factors

least

e a c h r u n was

as

for

one

on

than

hot

subject(36,

good

this

of

the

solutes

Therefore, work.

the Its

con

compounds

with

phase.

aromatic

in triplicates.

better

of

on t h i s

and sodium n i t r a t e

ppm i n

made

determination

s t i l l

study

i n reversed-phase

100

of

were

of

were

easily

and t h i s

our knowledge

was

LC systems

of

(1)

i n pure a c e t o n i t r i l e

a number

measurements

various

was

s o d i u m n i t r i t e was

used

a K o m a t s u DW

(Tokyo,

was

concentration

sodium n i t r i t e

of

in

FineSIL

phase

columns

test

column v o i d - t i m e

time

placed

commercially

The

(30-35)

From

decided

measure

the

detector

use.

been

void-volume

the

0.1°C.

Jasco

were

Uvidec-

as

tubings

mobile

a Microfeeder MFpump a n d a

Japan)

HPLC g r a d e

value

a

were +

Chemicals

the

a solute

in

column

to

Kanto of

dissolved

phase

(4) of

constant

in

If

(PTFE

and

substances

a

phase,

(ppm).

phase,

Cp)

measurements until

20

slurry technique;

consisted

rate

at

of

the

Tokyo,

The columns kept

as

urn, N o m u r a C h e m i c a l s ,

jmm,

phases

consisted

Japan)

(Jasco,

columns

(5

substance.

mobile

million the

of

phase

test

each

C8

The f l o w

to

mobile

nm.

the

purchased from

sources.

the

p r e p a r e d by

Develosil

velosil

260

thermostat

reversed-phase

were

urn),

Japan)

used

L t d . , Tokyo,

spectrometer

nm a n d / o r

Four long)


chromatographic system

(Azuma E l e c t r i c ,

1.0

The

average

% relative

standard

deviation. Multiple 800

computer

regression

analyses

(Mitsubishi

computer

system

NEC

(Nippon E l e c t r i c ,

9801

were

written

Results In

the

18

PAHs

and

for

retention

i n BASIC

study,

a n d 28

polar

the

and

acetonitrile-water.

reversed-phase order

to

the

followings

were

log

is

π

;

V ,

A ;

it

w

features

the

use

o f aMELCOM

Japan).

16-bit

Japan),

The

microcomputer and the

programs

the

with mobile

i t

the

they

of

here

20

were

phases

relationships

molecular

logarithm of

and the

is

of

values

benzenes

of

between

we c a l l

properties

alkylbenzenes, determined

retention

and

"descriptors", of

a

on

methanol-water

solute,

as

the

selected:

the

water the w

columns

establish

factor

substituted

physicochemical parameters,

describing ;

a

L t d . , Tokyo,

capacity

groups

four

Ρ

p r e d i c t i o n was

Co.,

by

L t d . , Osaka,

language.

the

In

performed

Co.,

Discussion

present

various

were

Electric,

measure

composing

partition coefficient

the

hydrophobicity of

hydrophobic substituent

hydrophobicity of are

the of

calculated a molecule

the

substituted

from the (40).

constant

van V

w

is

der the

as

group Waals van

in

the

1-octanol/

measure

a molecule

radii der

in

a molecule

of

Waals


the

(38). of (39).

atoms

volume

and


170 A F

;

c

is

w

t h e van d e r Waals

correlation bonds)

+

factor,

(number

non-aromatic σ

η

HA,HD

;

Hammett's

;

they

surface is

c

area.

calculated

as Fc=(number

o f primary and secondary

ring

carbons)

of

double

-

0.5

for

(41,42).

constant.

are parameters

HA i s is

F

equal

equal

to

to

showing

t h e number

t h e number

the extent

o f hydrogen

o f hydrogen

of

substituted

acceptor

groups;

groups

donar groups i n a

a n d HD

molecule

(39).


From

the basic

groups

substituted

highly

promising to

the

four

and

l o g Ρ a r e good

C18

a n d Cp c o l u m n s ,

ively. good

different

ability

equations

of

analyses tions

i n Table

for retention

are only

compositions,

the

f o r each form

were

regression

compound's as

multiple group

X=X

2

log k'

= a Pi

X=X

n

l o g k»

= a Pi

and system

2

n

t h e volume

+

c^

+ b P2

+

c

+ b P

+ c

2

2

n

fraction

2

of

and a and b a r e the c o e f f i c i e n t s respectively

and c

experimental

conditions.

is

where

m is

cients and each

the

regression The

mobile

equa phase

by

The r e l a t i o n

described

i n the

= f !

(X)

=

jjj

diX

b

= f

2

(X)

=

1

e ^

c

= f

3

(X)

=

i

fjX*

t h e number

χ

x

less to

5 c a n be d e r i v e d ,

modifier

and η i s as

i n the mobile

descriptors, t h e number

functions

the following

regression

a

corresponding

(2·)

n

organic

correlated,

by t h e m u l t i p l e

log

c a n be

mobile

be o b t a i n e d

analysis.

corresponding

b and c c a n be e x p r e s s e d

compounds'

for η different should

2

the intercept,

and X - c are h i g h l y obtained

ah are

follows: + biP

be

are

hydrogen

π and

compounds.

c

respect

results,

the fixed

descriptions

with

= aiPi

X-b

at

η equations

1

a,

the

by t h e m u l t i p l e

the following

log k

If

indicates

aromatic

F

with

π a n d (HA-HD)

For phenols,

descriptions

1

X is

of

and PAHs,

retention

By t h e above

obtained

description

X=X

where

(HA-HD)

are

LC w i t h

C8 a n d C2 c o l u m n s ,

molecule.

the retention

same p r o c e d u r e s

ship

i n reversed-phase

phenol's,

columns.

and p o l a r

follows

however.

compositions,

general

I

the retention

To g e n e r a l i z e phase

except

instance,

the four

PAHs

as

for alkylbenzenes

and l o g Ρ with

w

stating

for describing their

t h e whole

with

listed

phases:

benzenes

In t h i s

descriptors

the retention

descriptors and A

alkylbenzenes,

the descriptors

describe

For substituted

accepting

o n QSRR f o r

stationary

descriptors.

good

studies benzenes,

of X, three

of

namely,

(3) (4) (5)

than η and d ^ ,

the following

= f (X)P 1

1

can

analyses:

1

" i " powers

of X.

e^

and f i

If

such

equation-6

are the

equations

will

+ f (X)P 2

2

+ f (X) 3

,

i f X-a,

equations

1

2

examined

coeffi as

be o b t a i n e d

group. k'

phase

Ρχ and P

(6)


3,

4

for

10.

Table

I.

Retention

f o r aromatic

ship

is


by m u l t i - c o m b i n a t i o n

compounds,

where

o f two

the following

171

descrip

relation

k

= a

1

Ρ

+ b P

λ

+ c

2

(2)

a n d PAHs

and mobile

phase*-*-

P^

P

a

2

b

c

r*2

C18

A

log Ρ F

c

0.187

0.029-0.552

0.990

C18

M

log Ρ F

c

0.230

0.056

0.989

-0.847

C8

A

A

w

l o g Ρ 0.070

0.067

-0.331

0.983

C8

M

A

w

l o g Ρ 0.107

0.095

-0.634

0.989

Cp

A

log Ρ F

c

0.235-0.022

-0.213

0.995

Cp

M

log Ρ F

c

0.325-0.016

-0.663

0.996

C2

A

A

w

l o g Ρ 0.049

0.090

-0.284

0.979

Ç2

M

A

w

l o g Ρ 0.010

0.056

-0.829

0.982

polar

groups

column

(c)

Retention Prediction

assumed:

alkylbenzenes column

(b)

descriptions

tors

log (a)

Microcomputer-Assisted

JINNO A N D KAWASAKI

substituted

and mobile

benzenes

phase

P i

p

except

phenols

a

2

b

c

r

C18

Â

π (HA-HD)

0.136-0.049

-0.007

C18

Μ

π (HA-HD)

0.130-0.048

-0.050

0.925

C8

Α

(HA-HD)

0.240-0.031

0.215

0.965

C8

Μ

π (HA-HD)

0.283-0.045

0.117

0.978

Cp

Α

(HA-HD)

0.178-0.025

0.222

0.976

Cp

Μ

0.191

0.005

0.106

0.982

C2

Α

(HA-HD)

0.234-0.017

0.212

0.950

C2

Μ

π (HA-HD)

0.273-0.010

-0.098

0.982

π π

π (HA-HD) π

0.959

phenols column

and mobile

phase

*2 r :

p

2

a

D

c

r

C18

Α

π

S*3

0.182

0.182

-0.368

0.952

C18

Μ

π

S

0.166

0.175

-0.343

0.974

C8

Α

π

S

0.294

0.080

-0.192

0.952

C8

Μ

π

S

0.343

0.099-0.235

0.979

Cp

A

π

S

0.220

0.131

-0.221

0.960

Cp

M

π

S

0.191

0.158

-0.401

0.970

C2

A

π

S

0.302

0.115

-0.103

0.953

C2

M

π

S

0.312

0.152

-0.171

0.956

*1 A : a c e t o n i t r i l e : w a t e r M:

i

p

methanol:water correlation

* 3 S = πσ, h

=75

=65 :

:

35.

25.

coefficient.

(1- π),



172 This modifier are

given,

mined of

equation in

for

the

the the

any

column has The column


Table

III

focused

were is

used were

factors

equations

in

capacity

factors 10

column other

suggests

for

to

structed

on t h e

RPS i s

the

shown

interactive

computer;

(1)

solutes,

(2)

fraction

of

the

mobile When

computer

and then phase

used

Then,

=

or

agree

to

use

the

the

the

measuredones

with

agreement the

C18

retention

on

RPS a s

(mobile

column of

the on

are the

formula

phase

phase

to

input

with

CRT o f

of

(M),

(X),

wascon

thisfunction

system

data

function

chemical

computer-

C18

flow-chart

of

mobile

using

predicted

good

the

the

following

the

C18

columns.

for

The

the

themeasured

the

fairly

predict

and

for

and

values

C18

II

compounds.

that

with

this

factor

the

conditions in

Figure 1

the

Table

p r e d i c t e d by

procedures,

accessing

names

or

suitable

capacity

input the

can be

in

(RPS)

the

theC18

the

interesting

volume

flow

rate

of

(F)). chemical

factors are

values

of

(k')

F,

the

mobile

Ν =

3482 F

2

the

input

input

solutes

to

RPS,

the

compounds' at

selected

theoretical

though

plate

modified

generally

Ν is

number, for a

Ν

is

thecolumn

function

of

phase. -

0

on

*

( 2 σ

(7)

4

the

drawn a c c o r d i n g

r

for

are

the

approximately

determined),

the

1/2/ίΓσ e x p ( - ( x - t ) /

for

predicted.

of

based

formulas

descriptors

relationship-7

chromatogram,

Gaussian, y

by

velocity

a

after

composition

the

In

solutes,

modifier

(experimentally

linear

of

for of

for

in

retention

C p a n d C2

mentioned

case

aromatic

values

course,

microcomputer.

experimental

compounds'

From

above

C8,

study.

equations

of

their

compounds

c o m p o u n d name

organic

groups

as

deter

concept

example

the

listed

Given the

the

basic

experiments

data

capacity

F i g u r e 2.

calculates

calculated

such

style

the

found

Of

only

compound

discussions.

s h o u l d be p o s s i b l e

times

phase

by the


in

the

mobile

a l l

typical

system,

retention

be

errors.

16-bit

retention

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in

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k'

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obtain

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the

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in

Table

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the

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the

been

are

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the σ=

that

the

following t / / N , r

peak

band

is

equation-8;

t -4

σ

r

Chromatography and Separation Chemistry - ACS Publications

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