Matrix effects in Fast Atom Bombardment (FAB) mass spectrometry

International

Journal of Mass Spectrometry

Elsevier Scientific

MATRIX

J.

EFFECTS

NEIL1

Swiss

Publishing

Company,

IN FAST

367

and Ion Physics, 46 (1983) 367-370

Amsterdam

-Printed

in The Netherlands

ATOM BOMBARDMENT

(FAR) MASS

SPECTROMETRY

of Technology,

Laboratorium

of Organic

and 3. SEIBL

Federal

Institute

16, CH-8092

Universit4tsstr.

Chemistry,

Zijrich, Switzerland

ABSTRACT as matrices in Several organic liquids were evaluated for their effectiveness Differences in the sample spectrum fast atom bombardment (FAB) mass spectrometry. ion yield and chemical interactions between sample such as matrix supression, and matrix molecules were observed. The known selectivity of a lipophilic diamide for lithium is retained in the FAB environment. The mass spectrum of folic acid was obtained and its unusual behaviour in the particular system used is presentad.

INTRDDUCTIDN Fast atom bombardment analysis

(FAB) has recently

by MS and is accepted

without

due to its technical

simplicity

which

1.5 years

is known

and is caused

since

sample

admission,

sample

over

Since

little

cause

several

desirable

RESULTS

extended

about

compound

to investigate

types

do not yield

other

giving

replenishes

analysis

system,

for achieving

for

the

possible.

rise to this feature

to the glycerol

possibilities

is interesting

as a matrix

if used

convenient

community

That a method

important

which

organic

and be-

it seems

accordinq

results.

and DISCUSSION

In order screening

to possibly

experiments,

get some leading the matrix

diverse

degrees

of polarity,

stances

in Fig.

1 were

and boiling

point

The results which

suddenly

of a carrier,

of time to render

in

by the professional

(ref. 2) that glycerol,

the mechanisms

appearance

for its capability.

becomes

the properties

periods

is known

I.)

(ref.

an amazing

hesitation

and the need

by the discovery exhibits

made

both

obtained

investigated,

with

did not give any

or not acids,

bases

or salts

00~~~3~~/33/0~0~000/$03.00

compounds

acidity

to be handled

folio

were

infosmation

were

chosen

and lipophilicity. all being

conveniently

useful

0

trend

liquids

outside

added

with

to assist

1983 Elsevier Scientific

of

such as to represent Among others, of suitable

and inside

acid and a lipophilic FA3 spectra

from the results

diamide

glycerol,

viscosity

the ion source. are presented,

no matter

ion formation. Publishing

the sub-

Company

whether

368

COOC,H,

CHi_ COOC,H,

(CH,),

HN

I COOC,H,

CH~COOC,H, TEC

HO -(CH,-CH,-

,CH,-

I

I I

HO-C-COOC,H,

CH,-

OBS

O),H

‘Linoleic

Fig.

1.

Substances

Fig.

2.

Structure

evaluated

of

folic

as

acid,

FAB

CH,OH

H,N-C-Cti,OH CH,-

‘C&OH

CH,OH

TRIS

9-octa*ecenoic

acid ‘Oleic

acid’

LA

0-NPOE

PEG

\

TEA

9,12,15-Octadecatrienoic acid

n=3-,5

N

CH,OH

DEA

0-C,Y,

,

,CH,-CCH,OH

CH,OH HO CH,-

\

acid’

OA

matrices

molecular

(except

weight:

TRIS:

441.

solvent

Fragment

modifier).

A:

295

443 295

547

u.

Fig.

3.

FAB

mass

spectrum

of folic

acid

(part).

Matrix:

I.

.I I ,

DEA.

matrix

_I”. . *

.J.

peaks:

_d,,,I

*

369

Folic

with

acid

these

matrices

achieved

by

mixing

with

DEA

shown

is

the

ion.

folic TRIS

matrix.

in

3.

fig. the (m/z

The

fragment

acid molecular and

which

TEA

are

three

acid

in a saturated

The

upper

The

major

547)

at

or peak

ion. peak

interpreted

On

at

around

mass peak

at

m/z

m/z

is

could

of

dilute

representing

exhibited

Signal

around

to by

KCtH

to

obtained

protonated

amide

cleavage

(M+K3)+

of

of

one molecular

of the

the

acid, appear

558 and 596

and

Mf’

where

a

520,

with

to

species

a mixture

m/z

(M+HtK2)+,

so

before

corresponds to

attached arise

was

of TRIS

spectrum

formally

signals

enhancement

solution

the

443

295

centering

and

correspond

563)

addition

TEA

aqueous with

masses

(m/z

and

m/z 440.

range

higher

TRIS

clusters

as

DEA

in

range

peaks

DEA

soluble

mass

the

acid, of

parent

in the

dissolving

dihydrofolic molecule

2) was best

(Fig.

(M-H+K4)+

in

this

sequence.

N,N,N;N~tetraisobutyl-cyclohexane-l,2-dicarboxamide selective

ligand

in

liquid

(Fig.4)

membrane

systems alkali

{ref. ions

mass

is

3).

Since

an

important

spectrometry,

to see retained and

it

whether

this

under

possibly

simple

FAB

Fig.

4.

Structure

selective Fig.1.

of

lipophilic

There

are

a

differences

determinations

(N+H)++(M-H)+

ions .

are

by

a

diamide

tained however,

for low level

because factor

of

appeared

thereby

in

which

useful

but

reasonable

all

other

render

higher

no

Fig.

5.

Absolute

intensities

FAB

interest is

of analysis

be tested

in a

TEC

signal than

FAB

spectrum

spectra

were

listed

the

adequate

most

intensities in

solubility

matrices

any

Intens,ty

r-l

of

in

selectivity

to its poor

gave

absolute 2

lithium by

process

conditions

could

as

fashion.

glycerol,

lithium

diamide.

known

cationization

cation

Presumably’due the

is

M

(M+n)+

0

(I+

of

the

for

in ob-

in matrix

(WI-H)+

others

and

(fig.5).

0‘

W5(M

-Ii)*

r of

(fl+H)+

and

(Pl+H)++(Pl-H)+

ions

(arbitrary

units).

370

Addition ty

of

Matrix

somewhat.

spectra

of

the

Cation alkali

analyte

in

molecular

formula

The

log

= signal

graphical

-

I(M+Li)+

-

results

lithium

Li

in

turns

out of

6 for

PEG

Li+ 10S7m

Li+

Kf

better

by

amounts and

system

with

+

-

Li

applying I(M+Li)+, (Hf,

PEG

and seems

as matrix

K+,Na+).

+ _

l_ll-7m

K+

10-

K+

10-7m

H+

1Um7m

K+ Na+

PEG Li+ 10e7m KC 1Cle7m

PEG Li+

7rn

+

-H

+

-H -K

+

-Li

Hf4x10-7m

Ma+

l.0-7m

N,N,N;NLteraisobutyl-

cyclohaxane-1,2_dicarboxamide

CONCLUSIONS of liquid

R variety where

glycerol

Solubility

fails.

important

parameter

or salts

can improve

addition

of

alkali

substances

organic

in

a

matrix

for FAR analysis

solution

utility

of a system.

Spiking

Cation

selectivity

lipophilic

or

as sample

the sensitivity.

salts

serve

of the sample

determines

which

can

was

is one with

observed

acids on

diatnide.

REFERENCES 1

F.M.

2

M. Barber, Anal.

3

A.F.

Anal.

Dsvienne,

J-C.

R.S.

Chsm., Zhukov,

Chim.Acta,

Rousteau,

Bardoli,

54(1982) D. Erne,

Org.

G.J.

pp D.

131(1981)

Mass

Elliot,

Spectrom.,

R.D.

Sedgewick,

17(1982> A.N.

pp 173-181 Taylor,

645A-657A

Ammann, pp

N.

117-122

Giiggi,

E.

Pretsch,

W.

of

the

other cations

+

PEG.

scanning

selectivity.

10m7rn

of

be

sensitiwi-

cleaner

Selectivity;

=

+

PEG

to

determined S

in

equimolar

and matrix

where

Fig.

+

-K

selectivity

results

mixtures

are

) ;

PEG enhances

which

ions -Li+veraus

shown

-

1f7m

adding

I(M+C)+

is

+

Lithium

6.

The

of adduct

+

hand

to the sample

-H

-K

other

by

+

-H

Fig.

/

significant

Li

the

to TEC and

HCl

interpretation,

region.

representation

-I

dilute

evaluated

intensity

indicate

-1

on

solution

ion (

of

easier

was

aqueous

clearly

0

for

parent

S =

I(M+C)+

amounts

supression

selectivity

salts

the

equimolar

Simon,

to