ICR Mass Spectrometer
2
Jürgen H. Gross Jürgen H. Gross 1 1 , H. Bernhard Linden , H. Bernhard Linden 2 2 1 Institute of Organic Chemistry, Heidelberg University, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany. 2 Linden CMS, Auf dem Berge 25, 28844 Leeste, Germany. Combined ESI/LIFDI Combined ESI/LIFDI - - Ion Source for a FT Ion Source for a FT - - ICR Mass Spectrometer ICR Mass Spectrometer Concept of the Bruker Dual Source MTP The Dual Source MTP™ available with Bruker ApexQe FT-ICR mass spectrometers simultaneously handles ions entering via the electrospray interface and ions emerging from the (MA)LDI target. ESI ions are deflected into an ion funnel while those from MALDI are traveling on-axis. Other ionization sources may be attached after removal of the MALDI assembly from the ion source housing. 59 th ASMS Conference on Mass Spectrometry, Denver, CO, June 5-9, 2011 TP 056 Advantages of LIFDI In LIFDI the sample transfer capillary delivers the analyte in solution directly onto the emitter positioned in the high vacuum of the ion source. The capillary is fed through a drilled hole in the glass insulator bearing the emitter-holding metal pins. The liquid bridges the narrow gap between the end of the capillary and the activated emitter, and thus, prevents it from mechanical damage. The photograph shows solvent wetting the emitter. Activated Emitter Emitter Pins Sample Transfer Capillary Liquid Wetting the Emitter Glass Insulator with Drilled Hole Upper photograph: Standard configuration of the Dual Source MTP. The rear panel with the entire MALDI unit is replaced by the LIFDI unit. Both cable connections are extended to avoid errors of the data system. Lower photograph: Open source housing with the LIFDI unit attached. After closing the rear panel the LIFDI probe can further be inserted until the tip is located between the first electrodes of the ion funnel. The emitter is illuminated by a white LED light to enable observation of sample transfer by a video camera. Mounting of a LIFDI Unit The Dual Source MTP of the Bruker ApexQe FT-ICR mass spectrometer in our lab is capable of simultaneously collecting ions from both ESI interface and MALDI sample plate. This is achieved by an ion funnel operated under rough vacuum of 1.8 mbar. After removal of the housing’s rear panel this position is open to accept any other ion source. The prototype LIFDI unit attached to the ApexQe replaces the rear panel of the the ion source housing. The LIFDI probe is aligned as to position the emitter axially into the ion funnel entrance. After closing the entrance of the ESI transfer capillary with a septum the pressure inside the ion source housing drops to about 8 x10 -3 mbar by the action of the rotary pump alone. Adding a turbomolecular pump (260 l s -1 ) to the housing delivers high vacuum of 3 x 10 -5 mbar. a d c ESI Interface Entrance of the ESI transfer capillary Rear panel bearing the MALDI sample stage Rear panel bearing LIFDI unit and turbo pump on its outside ESI transfer capillary Feed through and guide for LIFDI probe Ion funnel Emitter Liquid injection field desorption/ionization (LIFDI) ideally complements ESI to ionize nonpolar analytes. Additionally, LIFDI handles compounds sensitive to oxidation or hydrolysis by providing sample supply under inert conditions [1,2]. As LIFDI has proven capabilities on our sector instrument and on FT-ICR instrumentation elsewhere [3,4], it appeared promising to adapt a LIFDI source to a hybrid quadrupole-FT-ICR instrument such as the Bruker ApexQe. Acknowledgment The Deutsche Forschungsgemeinschaft (DFG) and SFB 623 are acknowledged for funding the FT-ICR instrument and Deutscher Akademischer Austausch- dienst (DAAD) for a travel grant to J. H. G. We are indebted to Prof. W. Krätschmer for a sample of C 60 , to Prof. U. Bunz for 3,4,5-tridodecyloxy- benzaldehyde, to Dr. S. Weidner for polystyrenes, and to N. Nieth for measuring reference spectra on our JMS 700 sector instrument. We thank Bruker Daltonik, Bremen, for assistance with parts of the ion source housing and helpful discussions. Illustration of the working principle of the Dual Source MTP accepting ions from two different points of origin at the same time. Scheme courtesy of Bruker Daltonik, Bremen. Construction and Operation of the ESI/LIFDI Combination Source The new ESI/LIFDI combination ion source can readily be switched to ESI operation. To do so, the turbomolecular pump is switched off, the LIFDI probe is retracted by 1 cm and the entrance of the ESI transfer capillary is opened. ESI spectra may then be acquired after about 2 min vacuum adjustment time. The electrostatic charging of the focusing electrodes at the LIFDI probe’s tip serves to deflect ions into the ion funnel and thereby replaces the standard deflection electrode. Switching between positive-ion and negative-ion mode requires about 15 s due to the time required for proper charging of these electrodes. Besides that, there is no noteworthy difference between ESI operation with the LIFDI unit mounted and ESI with the standard configuration of the Dual Source MTP. This is the first ESI/LIFDI combination ion source: a prototype developed for a Bruker ApexQe instruments featuring an ion funnel. Schematic of the LIFDI unit mounted to the ion source housing of the ApexQe instrument. The emitter is positioned in the high vacuum of the ion source housing between the first electrodes of the ion funnel. The additional turbomolecular pump is mounted to the rear panel and evacuates the ion source housing. Sealing of the ESI transfer capillary is achieved by a septum on its entrance (inserted photograph). White LED light Handouts for Download Handouts of this poster in PDF format can be downloaded after this ASMS conference at http://www.linden-cms.de and at http://www.rzuser.uni-heidelberg.de/~bl5
Transcript of ICR Mass Spectrometer
Jürg
en H
. Gro
ss
Jürg
en H
. Gro
ss 11
, H. B
ernh
ard
Lind
en
, H. B
ernh
ard
Lind
en 22
1In
stitu
te o
f Org
anic
Che
mis
try,
Hei
delb
erg
Univ
ersi
ty, I
m N
euen
heim
er F
eld
270,
691
20 H
eide
lber
g, G
erm
any.
2
Lind
en C
MS,
Auf
dem
Ber
ge 2
5, 2
8844
Lee
ste,
Ger
man
y.
Com
bine
d ES
I/LI
FDI
Com
bine
d ES
I/LI
FDI --
Ion
Sour
ce fo
r a
FTIo
n So
urce
for
a FT
-- ICR
Mas
s Sp
ectr
omet
erIC
R M
ass
Spec
trom
eter
Conc
ept o
f the
Bru
ker
Dua
l Sou
rce
MTP
The
Dua
l Sou
rce
MTP
™ a
vaila
ble
with
Bru
ker
Apex
Qe
FT-I
CR
mas
s sp
ectr
omet
ers
sim
ulta
neou
sly
hand
les
ions
ent
erin
g vi
a th
e el
ectr
ospr
ay in
terf
ace
and
ions
em
ergi
ng fr
om th
e (M
A)LD
I tar
get.
ESI i
ons
are
defle
cted
into
an
ion
funn
el w
hile
th
ose
from
MAL
DI a
re tr
avel
ing
on-a
xis.
Oth
er io
niza
tion
sour
ces
may
be
atta
ched
aft
er r
emov
al o
f the
MAL
DI
asse
mbl
y fr
om th
e io
n so
urce
hou
sing
.
59th
ASM
S Co
nfer
ence
on
Mas
s Sp
ectr
omet
ry, D
enve
r, C
O, J
une
5-9,
201
1
TP 0
56
Adva
ntag
es o
f LIF
DI
In L
IFD
I the
sam
ple
tran
sfer
cap
illar
y de
liver
s th
e an
alyt
e in
sol
utio
n di
rect
ly
onto
the
emitt
er p
ositi
oned
in th
e hi
gh v
acuu
m o
f the
ion
sour
ce. T
he
capi
llary
is fe
d th
roug
h a
drill
ed h
ole
in th
e gl
ass
insu
lato
r be
arin
g th
e em
itter
-hol
ding
met
al p
ins.
The
liqu
id b
ridge
s th
e na
rrow
gap
bet
wee
n th
e en
d of
the
capi
llary
and
the
activ
ated
em
itter
, and
thus
, pre
vent
s it
from
m
echa
nica
l dam
age.
The
pho
togr
aph
show
s so
lven
t wet
ting
the
emitt
er.
Act
ivat
ed E
mitt
erEm
itter
Pin
s
Sam
ple
Tran
sfer
C
apill
ary
Liqu
id
Wet
ting
the
Emitt
er
Gla
ss In
sula
tor w
ithD
rille
d H
ole
Uppe
r ph
otog
raph
: Sta
ndar
d co
nfig
urat
ion
of th
e D
ual S
ourc
e M
TP.
The
rear
pan
el w
ith th
e en
tire
MAL
DI u
nit i
s re
plac
ed b
y th
e LI
FDI
unit.
Bot
h ca
ble
conn
ectio
ns a
re e
xten
ded
to a
void
err
ors
of th
eda
ta
syst
em.
Low
er p
hoto
grap
h: O
pen
sour
ce h
ousi
ng w
ith th
e LI
FDI u
nit
atta
ched
. Aft
er c
losi
ng th
e re
ar p
anel
the
LIFD
I pro
be c
an fu
rthe
r be
in
sert
ed u
ntil
the
tip is
loca
ted
betw
een
the
first
ele
ctro
des
of th
e io
n fu
nnel
. The
em
itter
is il
lum
inat
ed b
y a
whi
te L
ED li
ght t
o en
able
ob
serv
atio
n of
sam
ple
tran
sfer
by
a vi
deo
cam
era.
Mou
ntin
g of
a L
IFD
I Uni
t
The
Dua
l Sou
rce
MTP
of t
he B
ruke
r Ap
exQ
e FT
-ICR
m
ass
spec
trom
eter
in o
ur la
b is
cap
able
of
sim
ulta
neou
sly
colle
ctin
g io
ns fr
om b
oth
ESI
inte
rfac
e an
d M
ALD
I sam
ple
plat
e. T
his
is a
chie
ved
by a
n io
n fu
nnel
ope
rate
d un
der
roug
h va
cuum
of
1.8
mba
r. A
fter
rem
oval
of t
he h
ousi
ng’s
rea
r pa
nel t
his
posi
tion
is o
pen
to a
ccep
t any
oth
er io
n so
urce
. The
pro
toty
pe L
IFD
I uni
t att
ache
d to
the
Apex
Qe
repl
aces
the
rear
pan
el o
f the
the
ion
sour
ce h
ousi
ng. T
he L
IFD
I pro
be is
alig
ned
as to
po
sitio
n th
e em
itter
axi
ally
into
the
ion
funn
el
entr
ance
. Af
ter
clos
ing
the
entr
ance
of t
he E
SI tr
ansf
er
capi
llary
with
a s
eptu
m th
e pr
essu
re in
side
the
ion
sour
ce h
ousi
ng d
rops
to a
bout
8 x
10-3
mba
r by
th
e ac
tion
of th
e ro
tary
pum
p al
one.
Add
ing
a tu
rbom
olec
ular
pum
p (2
60 l
s-1 )
to th
e ho
usin
g de
liver
s hi
gh v
acuu
m o
f 3 x
10-
5m
bar.
a
d
c
ESI I
nter
face
Entr
ance
of t
he E
SI
tran
sfer
cap
illar
y
Rea
r pan
el b
earin
g th
e M
ALD
I sam
ple
stag
e
Rea
r pan
el
bear
ing
LIFD
I uni
t an
d tu
rbo
pum
p on
its
outs
ide
ESI t
rans
fer
capi
llary
Feed
thro
ugh
and
guid
e fo
r LIF
DI p
robe
Ion
funn
elEm
itter
Liqu
id in
ject
ion
field
des
orpt
ion/
ioni
zatio
n (L
IFD
I) id
eally
com
plem
ents
ESI
to io
nize
non
pola
r an
alyt
es.
Addi
tiona
lly, L
IFD
I han
dles
com
poun
ds s
ensi
tive
to
oxid
atio
n or
hyd
roly
sis
by p
rovi
ding
sam
ple
supp
ly
unde
r in
ert c
ondi
tions
[1,2
]. As
LIF
DI h
as p
rove
n ca
pabi
litie
s on
our
sec
tor
inst
rum
ent a
nd o
n FT
-ICR
inst
rum
enta
tion
else
whe
re
[3,4
], it
appe
ared
pro
mis
ing
to a
dapt
a L
IFD
I sou
rce
to a
hy
brid
qua
drup
ole-
FT-I
CR in
stru
men
t suc
h as
the
Bruk
er A
pexQ
e.
Ackn
owle
dgm
ent
The
Deu
tsch
e Fo
rsch
ungs
gem
eins
chaf
t (D
FG) a
nd
SFB
623
are
ackn
owle
dged
for
fund
ing
the
FT-I
CR
inst
rum
ent a
nd D
euts
cher
Aka
dem
isch
er A
usta
usch
-di
enst
(DAA
D) f
or a
trav
el g
rant
to J.
H. G
. W
e ar
e in
debt
ed to
Pro
f. W
. Krä
tsch
mer
for
a sa
mpl
e of
C 6
0, to
Pro
f. U.
Bun
z fo
r 3,
4,5-
trid
odec
ylox
y-be
nzal
dehy
de, t
o D
r. S
. Wei
dner
for
poly
styr
enes
, and
to
N. N
ieth
for
mea
surin
g re
fere
nce
spec
tra
on o
ur JM
S 70
0 se
ctor
inst
rum
ent.
We
than
k Br
uker
Dal
toni
k, B
rem
en, f
or a
ssis
tanc
e w
ith
part
s of
the
ion
sour
ce h
ousi
ng a
nd h
elpf
ul d
iscu
ssio
ns.
Illus
trat
ion
of th
e w
orki
ng p
rinci
ple
of th
e D
ual S
ourc
e M
TP a
ccep
ting
ions
from
tw
o di
ffer
ent p
oint
s of
orig
in a
t the
sam
e tim
e. S
chem
e co
urte
syof
Bru
ker
Dal
toni
k, B
rem
en.
Cons
truc
tion
and
Ope
ratio
n of
the
ESI/
LIFD
I Com
bina
tion
Sour
ceTh
e ne
w E
SI/L
IFD
I com
bina
tion
ion
sour
ce c
an r
eadi
ly b
e sw
itche
dto
ESI
ope
ratio
n. T
o do
so
, the
turb
omol
ecul
ar p
ump
is s
witc
hed
off,
the
LIFD
I pro
be is
ret
ract
ed b
y 1
cm a
nd th
e en
tran
ce o
f the
ESI
tran
sfer
cap
illar
y is
ope
ned.
ESI
spe
ctra
may
then
be
acqu
ired
afte
r ab
out 2
min
vac
uum
adj
ustm
ent t
ime.
The
ele
ctro
stat
ic c
harg
ing
of th
e fo
cusi
ng e
lect
rode
s at
the
LIFD
I pro
be’s
tip
serv
es to
def
lect
ions
into
the
ion
funn
el a
nd th
ereb
y re
plac
es th
e st
anda
rd d
efle
ctio
n el
ectr
ode.
Sw
itchi
ng b
etw
een
posi
tive-
ion
and
nega
tive-
ion
mod
e re
quire
s ab
out 1
5s
due
to th
e tim
e re
quire
d fo
r pr
oper
cha
rgin
g of
thes
e el
ectr
odes
. Be
side
s th
at, t
here
is n
o no
tew
orth
y di
ffer
ence
bet
wee
n ES
I ope
ratio
n w
ith th
e LI
FDI u
nit
mou
nted
and
ESI
with
the
stan
dard
con
figur
atio
n of
the
Dua
l Sou
rce
MTP
.
This
is th
e fir
st E
SI/L
IFD
I co
mbi
natio
n io
n so
urce
: a
prot
otyp
e de
velo
ped
for
a Br
uker
Ape
xQe
inst
rum
ents
feat
urin
g an
ion
funn
el.
Sche
mat
ic o
f the
LIF
DI u
nit m
ount
ed to
the
ion
sour
ce h
ousi
ng
of th
e Ap
exQ
e in
stru
men
t. Th
e em
itter
is p
ositi
oned
in th
e hi
gh v
acuu
m o
f the
ion
sour
ce h
ousi
ng b
etw
een
the
first
el
ectr
odes
of t
he io
n fu
nnel
. The
add
ition
al tu
rbom
olec
ular
pu
mp
is m
ount
ed to
the
rear
pan
el a
nd e
vacu
ates
the
ion
sour
ce h
ousi
ng.
Seal
ing
of th
e ES
I tra
nsfe
r cap
illar
y is
ach
ieve
d by
a s
eptu
m o
nits
ent
ranc
e (in
sert
ed p
hoto
grap
h).
Whi
te L
ED li
ght
Han
dout
s fo
r D
ownl
oad
Han
dout
s of
this
pos
ter
in P
DF
form
at c
an b
e do
wnl
oade
d af
ter
this
ASM
S co
nfer
ence
at
http
://w
ww
.lind
en-c
ms.
dean
d at
ht
tp:/
/ww
w.r
zuse
r.un
i-he
idel
berg
.de/
~bl5
Expe
rimen
tal
Expe
rimen
ts a
re p
erfo
rmed
on
a 9.
4T
Bruk
er A
pexQ
e FT
-ICR
(Qh-
ICR
hybr
id) i
nstr
umen
t with
Dua
l Sou
rce
MTP
(ESI
-to-
MAL
DI s
witc
habl
e). T
he
stan
dard
MAL
DI s
ampl
e st
age
and
the
defle
ctio
n el
ectr
ode
at th
e en
tran
ce o
f th
e io
n fu
nnel
are
rep
lace
d by
the
LIFD
I uni
t com
pris
ing
vacu
um lo
ck, p
robe
, tu
rbom
olec
ular
pum
p, o
bser
vatio
n op
tics,
and
vac
uum
gau
ge. F
or E
SI
oper
atio
n, th
e LI
FDI p
robe
is r
etra
cted
and
its
focu
sing
ele
ctro
des
are
used
to
defle
ct io
ns in
to th
e fu
nnel
. In
LIFD
I mod
e, th
e ES
I tra
nsfe
r ca
pilla
ry is
sea
led
by a
sep
tum
to a
chie
ve <
4×
10–5
mba
r. L
IFD
I spe
ctra
are
acq
uire
d at
em
issi
on-c
ontr
olle
d io
n cu
rren
ts o
f 4×
10–8
mA.
Typi
cally
, ion
s ar
e ac
cum
ulat
ed fo
r 1–
5s
per
tran
sien
t and
then
tran
sfer
red
into
the
ICR
cell.
16–
64 tr
ansi
ents
with
1M
dat
a po
ints
are
acq
uire
d in
po
sitiv
e-io
n br
oadb
and
mod
e.Th
e tim
e-do
mai
n da
ta a
re z
ero-
fille
d an
d ap
odiz
ed b
y a
sine
-bel
l fun
ctio
n pr
ior
to F
ourie
r tr
ansf
orm
atio
n to
del
iver
a
mag
nitu
de s
pect
rum
.
Acqu
isiti
on is
con
trol
led
by B
ruke
r Ap
exCo
ntro
l 3.0
.0 s
oftw
are,
dat
a an
alys
is
is p
erfo
rmed
usi
ng th
e Br
uker
Dat
aAna
lysi
s 4.
0 so
ftw
are.
Tuni
ng o
f the
LIF
DI s
ourc
e is
ach
ieve
d us
ing
the
pers
iste
nt c
atio
n si
gnal
of
trih
exyl
(tetr
adec
yl)p
hosp
honi
um tr
is(p
enta
fluor
oeth
yl)t
riflu
orop
hosp
hate
,an
ioni
c liq
uid
[5].
Thus
, the
pot
entia
ls fo
r io
n tr
ansf
er fr
om th
e fie
ld e
mitt
er
thro
ugh
the
ion
funn
el in
to th
e hQ
h-in
terf
ace
are
adju
sted
. Pol
yeth
ylen
e gl
ycol
600
(bel
ow) a
nd P
EG15
00 a
re u
sed
for
exte
rnal
mas
s ca
libra
tion
to
assu
re m
ass
accu
raci
es o
f 1pp
m in
ESI
and
LIF
DI m
odes
of o
pera
tion.
LIFD
I spe
ctru
m o
f PEG
60
0 af
ter
exte
rnal
ca
libra
tion.
Rel
evan
t pa
ram
eter
s ar
e lis
ted
in th
e he
ader
.
Appl
icat
ions
of t
he N
ew E
SI/L
IFD
I Com
bina
tion
Sour
ce
OH
O
O
OC
12H
25
C12
H25
H25
C12
OH
O
O
OH
C12
H25
H25
C12
McL
-C12
H24
+.
+.
m/z
490
,401
6
m/z
658
,589
7
LIFD
I spe
ctru
m o
f 3,
4,5-
trid
odec
ylox
y-be
nzal
dehy
de
LIFD
I spe
ctra
of
[60]
fulle
rene
un
der
diff
eren
t tr
appi
ng
cond
ition
s
Qh
gas
1.0
l/s
Trap
ping
15
V
Inte
nsity
4 x
105
coun
ts
Qh
gas
1.35
l/s
Trap
ping
17
V
Inte
nsity
8 x
105
coun
ts
Qh
gas
1.2
l/s
Trap
ping
15
V
Inte
nsity
6 x
105
coun
ts
LIFD
I spe
ctra
of d
iffer
ent c
ompo
unds
are
obt
aine
d ex
hibi
ting
good
in
tens
ity w
hen
clos
ed-s
hell
ions
suc
h as
[cat
ion]
+, [
M+
H]+
or [M
+N
a]+
are
form
ed. A
s us
ual i
n FD
-MS,
non
pola
r an
alyt
es p
refe
rabl
y de
liver
op
en-s
hell
mol
ecul
ar io
ns, M
+• ,
mor
e re
adily
und
ergo
ing
radi
cal-
indu
ced
diss
ocia
tions
. The
refo
re, s
pect
ra o
f non
pola
r co
mpo
unds
are
stil
l so
mew
hat u
nsat
isfa
ctor
y du
e to
red
uced
ion
abun
danc
e an
d in
crea
sed
frag
men
tatio
n. P
resu
mab
ly, t
he p
ecul
iarit
ies
of th
e io
n op
tics
and
its
spec
ific
pres
sure
reg
imes
are
cau
sing
thes
e m
olec
ular
ion
loss
es. W
hile
th
e ov
eral
l tra
nsm
issi
on in
crea
ses
at h
ighe
r pr
essu
re, c
ollis
ion-
indu
ced
frag
men
tatio
n in
the
ion
funn
el r
egio
n an
d in
the
hexa
pole
acc
umul
atio
n io
n tr
ap c
ause
loss
es b
y di
ssoc
iatio
n(c
f. [4
, p. 1
321]
). Te
chni
ques
and
pa
ram
eter
s fo
r im
prov
emen
t are
bei
ng e
xplo
red.
Refe
renc
es[1
] Lin
den,
H.B
. Liq
uid
Inje
ctio
n Fi
eld
Des
orpt
ion
Ioni
zatio
n: a
New
Too
l for
Sof
t Ion
izat
ion
of S
ampl
es
Incl
udin
g Ai
r-Se
nsiti
ve C
atal
ysts
and
Non
-Pol
ar H
ydro
carb
ons.
Eur
. J. M
ass
Spec
trom
.200
4, 1
0, 4
59-4
68.
[2] G
ross
, J.H
.; N
ieth
, N.;
Lind
en, H
.B.;
Blum
bach
, U.;
Rich
ter,
F.J.;
Tau
cher
t, M
.E.;
Tom
pers
, R.;
Hof
man
n, P
. Li
quid
Inje
ctio
n Fi
eld
Des
orpt
ion/
Ioni
zatio
n of
Rea
ctiv
e Tr
ansi
tion
Met
al C
ompl
exes
. Ana
l. Bi
oana
l. Ch
em.
2006
, 386
, 52-
58.
[3] S
chau
b, T
.M.;
Rodg
ers,
R.P
.; M
arsh
all,
A.G
.; Q
ian,
K.;
Gre
en, L
.A.;
Olm
stea
d, W
.N. S
peci
atio
n of
Ar
omat
ics
in P
etro
leum
Ref
iner
y St
ream
s by
Con
tinuo
us F
low
FD
-FT-
ICR
Mas
s Sp
ectr
omet
ry. E
nerg
y &
Fuel
s20
05, 1
9, 1
566-
1573
.[4
] Sch
aub,
T.M
.; H
endr
icks
on, C
.L.;
Qui
nn, J
.P.;
Rodg
ers,
R.P
.;M
arsh
all,
A.G
. Ins
trum
enta
tion
and
Met
hod
for
Ultr
ahig
h Re
solu
tion
FD-F
T-IC
R-M
S of
Non
pola
r Spe
cies
. Ana
l. Ch
em.2
005,
77,
131
7-13
24.
[5] G
ross
, J.H
. Liq
uid
Inje
ctio
n Fi
eld
Des
orpt
ion/
Ioni
zatio
n M
ass
Spec
trom
etry
of I
onic
Liq
uids
. J. A
m. C
hem
. So
c. M
ass
Spec
trom
.200
7, 1
8, 2
254-
2262
.
Fina
l Sta
tem
ents
LIFD
I spe
ctra
of p
olar
and
ioni
c co
mpo
unds
ar
e re
adily
obt
aine
d.
LIFD
I spe
ctra
of n
onpo
lar
arom
atic
hy
droc
arbo
ns e
xhib
it in
tens
e m
olec
ular
ions
.
Mas
s ac
cura
cy is
equ
al to
ESI
mod
e.
Sour
ce c
an e
asily
be
switc
hed
back
and
fo
rth
betw
een
ESI a
nd L
IFD
I ope
ratio
n.
The
first
ESI
-to-
LIFD
I sw
itcha
ble
com
bina
tion
ion
sour
ce is
pre
sent
ed a
s a
wor
king
pro
toty
pe.
Colli
sion
s du
ring
ther
mal
izat
ion
and
trap
ping
pro
babl
y pr
even
t lab
ile m
olec
ular
io
ns fr
om s
urvi
ving
.
The
tran
smis
sion
of t
he io
n fu
nnel
can
be
redu
ced
upon
eva
cuat
ion
from
1.8
mba
r st
anda
rd p
ress
ure
to le
ss th
an 1
0-4
mba
r.
Mol
ecul
ar io
ns o
f alip
hatic
hyd
roca
rbon
s ha
ve n
ot y
et b
een
obse
rved
.
LIFD
I spe
ctru
m o
f po
lyst
yren
e 10
50
