Use of ion clustering equilibrium for isomer identification in electron capture mass spectrometry
by Lisa A Krieger
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in
Chemistry
Montana State University
© Copyright by Lisa A Krieger (1987)
Abstract:
This work explores the possibility of isomer distinction by taking advantage of unique solvation
equilibrium constants for the clustering of ions with neutral solvating molecules. Each isomer would
exhibit a unique ratio of MS-/M- from a mass spectrum of the compound and the solvating molecule
which could theoretically be predicted if the equilibrium constant and the solvating molecule
concentration are known. This is assuming that equilibrium exists in the source, which is shown to be
true for the atmospheric pressure ionization source.
A number of substituted nitrobenzenes were tested with dimethylsulfoxide (DMSO) as the neutral
solvating molecule. These experiments showed that the method has promise, but is not as
straightforward as the theory predicts. An attempt was made to mathematically describe the observed
deviations from expectation. This resulted in an expression that closely described the system, but could
not calculate the reference value of Kf. USE OF ION CLUSTERING EQUILIBRIUM FOR ISOMER IDENTIFICATION
IN ELECTRON CAPTURE MASS SPECTROMETRY
by
L i s a A. K r i e g e r
A th e s i s subm itted in p a r t i a l f u lf i llm e n t
of th e req u ire m en ts fo r th e degree
of
M aster o f Science
in
C hem istry
MONTANA STATE UNIVERSITY
B o zem an, M o n ta n a
March 1987
MAIN UE
Oo^, J
ii
APPROVAL
o f a t h e s i s s u b m i t t e d by
L i s a A. K r i e g e r
T h i s t h e s i s h a s b e e n r e a d by e a c h m e m b e r o f t h e t h e s i s
c o m m i t t e e an d h a s b e e n f o u n d t o be s a t i s f a c t o r y r e g a r d i n g
c o n te n t, E nglish usage, form at, c i t a t i o n s , b ib lio g ra p h ic s ty le ,
a n d c o n s i s t e n c y , an d i s r e a d y f o r s u b m i s s i o n t o t h e C o l l e g e o f
G rad u ate S tudies.
lA /ll
Date
’
/
C h a ir p e r s o n , G ra d u a te Com m ittee
Approved f o r th e M ajor D epartm ent
%7
D ate
7
Head, Major D e p a rtm e n t
Approved f o r t h e C o lle g e o f G ra d u a te S t u d i e s
Date
Z
G r a d u a t e Dean
iii
STATEMENT OF PERMISSION TO USE
In p r e s e n tin g
re q u ire m e n t's
th is
thesis
in p a r t i a l
fo r a m a ste r's degree a t
f u l f i l l m e n t of the
Montana S t a t e
U niversity,
I a g r e e t h a t t h e L i b r a r y s h a l l make i t a v a i l a b l e t o b o r r o w e r s
under ru le s of th e L ibrary.
B r ie f q u o ta tio n s from t h i s
thesis
are a llo w ab le w ith o u t s p e c ia l perm issio n , provided th a t ac c u ra te
acknowledgement o f s o u r c e
i s made.
P e r m i s s i o n f o r e x t e n s i v e q u o t a t i o n from o r r e p r o d u c t i o n o f
t h i s t h e s i s may be g r a n t e d b y my m a j o r p r o f e s s o r ,
o r in h i s / h e r
a b s e n c e , b y t h e D i r e c t o r o f L i b r a r i e s w hen, i n t h e o p i n i o n o f
e i t h e r , th e proposed use of th e m a te r ia l is
purposes.
for sch o larly
Any c o p y i n g o r u s e o f t h e m a t e r i a l
in t h i s
f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n
perm ission.
th esis
for
iv
TABLE OF CONTENTS
Page
LIST
OF
TABLES
..................................................................................................... ■
v
LIST OF FIGURES .................. ............ ......................... .............. '.....................................
vi
ABSTRACT.........................................................................................
v iii
INTRODUCTION ........................................................................................................................
I
STATEMENT OF THE PROBLEM .........................................................................................
6
CHEMICAL DYNAMICS ...........................................................................................................
I
EXPERIMENTAL...................................................................................... '..............' ..............
12
CALCULATION OF EXPECTED Kf VALUES ..............................................................
23
RESULTS .........................................
26
SUMMARY............................................................................
58
LITERATURE CITED
61
V
LIST OF TABLES
T able
Page
1.
KfK V a l u e s f o r Compounds a t 7 0°C .......................... ...................................
2.
C a lc u la te d V alues o f
. ........................................................................
24
3.
I o n I n t e n s i t i e s a n d R V a l u e s f o r m-CFgNB/O.38 t o r r DMSO .
32
4.
S c a n Number
a n d R a t i o s f o r o-diNB/MeOH .............................................
34
5.
S c a n Number
and R a tio s
f o r m - d i N B / M e O H .............................................
35
6.
S c a n Number
a n d R a t i o s f o r p-diNB/MeOH ............................................
35
7.
P e a k A r e a s a n d R a t i o s f o r Some F l u o r i n a t e d N i t r o b e n z e n e s
8.
R e s u l t s o f P u l s e and R e s o l u t i o n E x p e r im e n ts f o r
p-CNNB/DMSO ............. ....................................................................................... -____
36
' 39
9.
C o n c e n t r a t i o n E f f e c t on t h e R a t i o o f
10.
C o m p a r i s o n o f Kr c a ^c a n d K^ k f o r
Some F l u o r o n i t r o b e n z e n e s f r o m E q u a t i o n 29 ....................................
47
C o m p a r i s o n o f Kfc a ^c a n d Kf K f o r
Some F l u o r i n a t e d N i t r o b e n z e n e s f r o m E q u a t i o n 30 .....................
57
11.
[MS“ ] / [ M ~ ] .........
3
40
vi
LIST OF FIGURES
F igure
Page
1.
F i r s t B u b b l e r ................................................... •....................................................
14
2.
S e c o n d B u b b l e r .........................................................................................
15
3.
ECD S o u r c e o f Mass S p e c t r o m e t e r w i t h
F r o n t F l a n g e .....................................................
17
4.
B l o c k D i a g r a m o f I n s t r u m e n t ........................................
18
5.
S a m p l e o f DIM P r i n t o u t
19
6.
DIM C i r c u i t .......................
20
7.
I o n S c a n o f m-CFgNB a n d DMSO ..................................................................
28
8.
I o n S c a n o f m-CFgNB a n d M e O H ..................................................................
29
9.
I o n S c a n o f o-NT w i t h an d w i t h o u t M e O H ............ ..............................
30
10.
I o n S c a n o f m-NT w i t h a n d w i t h o u t M e O H ................' ........................
30
11.
I o n S c a n o f p-NT w i t h a n d w i t h o u t MeOH ...........................................
31
12.
....................... * ...................... ................................
. MeOH a n d DMSO B a c k g r o u n d S c a n s ................................................
31
13.
In ten sity vs.
S c a n Number f o r m-CFgNB/MeOH................* ............
33
14.
I n te n s i ty vs.
S c a n Number f o r m-CFgNB/DMSO...............................
34
15.
S ingle
Ion M onitor
o f M-
a n d MS- f o r o - F N B / D M S O ...................
37
16.
S ingle
Ion M onitor
o f M-
a n d MS~ f o r m-FNB/DMSO...................
37
17 .
S ingle
Ion M onitor
o f M”
a n d MS- f o r p - F N B / D M S O ...................
38
18.
S ingle
Ion M onitor
o f M“
a n d MS” f o r m-CFgNB/DMSO ..............
38
19.
Ln K v s . 1 / T f o r V a r i o u s I o n E n e r g i e s , a n d f o r
C a l c u l a t e d P o i n t s f r o m K e b a r l e 1s D a t a .............. ..............................
41
Com parison o f
v s . [S] f o r O r i g i n a l
a n d I m p r o v e d B u b b l e r s ................................................... ...................... ..
43
20.
21.
v s
.
[S]
f o r m a n d p-OCHgNB ................................................................
44
v ii
22 .
Kf v s .
[S]
f o r p-CNNB ....................................................................................
23.
G e n e r a t e d P l o t o f Kg v s .
24.
[S]
45
f r o m E q u a t i o n 29 ...........................
48
1A 6 Xp v s * [S]
f o r m a n d p-OCHgNB w i t h DMSO ...................... . .
49
25.
1A exp v s .
[S]
f o r p-CNNB w i t h DMSO.........................
50
26.
1A exp v s .
[S] o - , m - , a n d p-FNB w i t h DMSO...........................
27.
1/R v s .
I / [S] f o r m- a n d p-OCHgNB w i t h DMSO.............................
53
28.
1/R v s .
1/[S]
f o r m- a n d p-FNB w i t h DMSO....................................
54
29.
1/R v s .
1/[S ]
f o r p-CNNB w i t h DMSO................................................
55
30 .
1/R v s .
I / [ S ] f o r S o l v a t i o n . by Two M o l e c u l e s o f EMSO
51
56
viii
ABSTRACT
T h i s w o r k e x p l o r e s t h e p o s s i b i l i t y o f i s o m e r d i s t i n c t i o n by
ta k in g advantage of u n ig u e s o l v a t i o n e g u i l i b r i u m c o n s t a n t s f o r
th e c lu s te r in g of ions w ith n e u tra l so lv a tin g m olecules.
Each
i s o m e r w o u l d e x h i b i t a u n i q u e r a t i o o f MS- / M ~ f r o m a m a s s
s p e c t r u m o f t h e com po u nd a n d t h e s o l v a t i n g m o l e c u l e w h i c h c o u l d
t h e o r e t i c a l l y be p r e d i c t e d i f t h e e q u i l i b r i u m c o n s t a n t and t h e
s o l v a t i n g m o l e c u l e c o n c e n t r a t i o n a r e known.
T h is i s assum ing
t h a t e q u i l i b r i u m e x i s t s i n t h e s o u r c e , w h i c h i s s h o w n t o be. t r u e
f o r th e atm o sp h eric p r e s s u r e io n i z a ti o n source.
A number o f s u b s t i t u t e d n i tro b e n z e n e s w ere t e s t e d w ith
d i m e t h y l s u l f o x i d e (DMSO) a s t h e n e u t r a l s o l v a t i n g m o l e c u l e .
These e x p e r i m e n t s showed t h a t t h e method h as p r o m i s e , b u t i s n o t
as s tra ig h tfo rw a rd as th e theory p re d ic ts .
An a t t e m p t was m a d e
to m a th e m a tic a lly d e s c r ib e th e o b se rv e d d e v ia tio n s from
ex p ectatio n .
T h is r e s u l t e d i n an e x p r e s s i o n t h a t c l o s e l y
d e sc rib e d th e sy stem , but could not c a lc u la te th e re fe re n c e v alu e
o f Kf .
I
INTRODUCTION
One o f t h e m o s t s e n s i t i v e
analysis
tw o
d etectio n
te ch n iq u es
for
i s e l e c t r o n - c a p t u r e m a s s s p e c t r o m e t r y (ECMS).
ro u tes
resonance
captured
the
electro n -ca p tu re
electro n
capture,
by a m o l e c u l e t o
process
w here
can
There a re
take.
a th e rm alized
trac e
One
is
electro n
is
form th e m o l e c u l a r a n i o n ,
as
sh o w n by
r o u t e la below .
The o t h e r i s d i s s o c i a t i v e e l e c t r o n c a p t u r e , a s
shown
lb ,
by
ro u te
m o lecu la r anion as
w hich
it
in v o lv es
the
d isso ciatio n
of
the
cap tu res the electro n .
MX-
(1)
MX + e - ( t h e r m a l )
M + XECMS i s
a sen sitiv e
technique
compared t o
re a c tio n s because e le c tro n -c a p tu re
o th er
i s one o f th e f a s t e s t i o n i c
r e a c t i o n s , havinq a r a t e
c o n s t a n t , ke c , up t o 4 x 10“
Ion-m olecule
are
c m 9/ s e c ,
w hich
cap tu re.
no
the
is
The
sen sitiv ity .
process
reactio n s
tw o o r d e r s
speed
The
analyte
fragm entation.
of
o th er
no
faster
than
reason
is
is
one
th a t
in
form s, th e m o le c u la r ion,
Thus,
id en tificatio n
m o n i to r e d from t h e same s i g n a l .
cm / s e c .
k jy m = I x
o f m aqnitude slo w e r
reac tio n
io n izatio n
than
reason
th e
M- ,
IO-9
electron
for
ECMS
resonance
w ith
little
and q u a n t i t a t i o n
can
EC
or
be
W i t h o n l y M~ b e i n g f o r m e d , t r a c e
2
am ounts
are
d etectab le
sin ce
c o n c e n t r a t e d o n o n e i o n , M- .
alth o u g h
i t p ro v id es
only
m olecule,
it
is
in
th e
w hich
im possible
to d is tin g u is h
if
and
co-w orkers
m olecular anions
by n e u t r a l
aceto n itrile,
so lv ato r,
have
is
present.
of
Since
th e
isom ers are
an aly sis,
isom ers
atom s
in
id e n tica l,
b e tw e e n them w i t h
it
the
thus
electro n -
been stu d y in g
the
solv atio n
of
m o lecu le s such as d im e th y l s u l f o x id e ,
S,
The m o l e c u l a r
to
ion,
form a c l u s t e r
re a c tio n re q u ire s a b u ffe r gas,
M- ,
io n ,
B, t o c o l l i s i o n a l l y
c l u s t e r ion so i t does n o t im m e d ia te ly f a l l a p a r t .
of reactio n
sig n al
t h e s i g n a l i s M- .
and m e th a n o l.1
by t h e n e u t r a l
av ailab le
for trac e
o rien tatio n
tw o o r more
c a p t u r e mass s p e c t r o m e t r y
K ebarle
sig n als
isom er i s
p h y sical
th e m asses of
to tal
T h e o n e p r o b l e m w i t h ECMS i s t h a t
sen sitiv e
o f te n does not i n d i c a t e
d iffer
th e
is
solvated
MS- .
stab ilize
T his
the
The r e v e r s e
2 a lso occurs.
(2)
M- + S ----> M S - *— § — =» MS-
The e q u i l i b r i u m e x p r e s s i o n f o r t h e s o l v a t i o n o f M- by S i s :
( 3)
Kf = [MS- ]
I mtTIsT
and th e n :
(4)
Kf [S]
=
[MS- ]
[M- ]
.
3
A c c o r d i n g t o K e b a r l e , 1 t h e Kf v a l u e s v a r y b e t w e e n i s o m e r s f o r
su b stitu ted
com pounds
n itro b en zen es
and
th e ir
(NB).
resp ectiv e
compounds, m e th a n o l, a c e t o n i t r i l e
Table
I.
Compound
compound,
Kf
I sh o w s some o f t h e s e
values
for
th e
so lv atin g
and d i m e t h y l s u l f o x i d e .
Kf K V a l u e s f o r Compounds a t 7 O0 C
CH3OH
CH3CN
DMSO
O-FNB
iH
in
Since
T able
m-FNB
3. 6 x IO3
6 .5 x 103
9 . 8 x IO4
p-FNB
7 . 0 x IO 3
1 .0 x 104
1 .6 x IO5
o-diNB
1 . 3 x IO2
1 . 2 x IO3
8 . 9 x IO 3
m-diNB
2 . 5 x IO 2
5 . 2 x IO2
5 . 3 x IO3
p-diNB
3 . 0 x IO1
1 . 0 x IO2
6 . 6 x IO2
Kf
the
is
x IO 3
d ep en d e n t upon
value
[MS- ] / [ M ~ ]
accordance w ith e q u a tio n
4.
isom eric d iffe re n c e s
s h o u ld change w i t h
the
of
a given
isom er in
T his s o lv a tio n e q u i lib r i u m
could
th e n be a p p lie d to a n a l y t i c a l m ass s p e c tr o m e tr y assum ing f i v e
co n d itio n s:
4
1.
The e q u i l i b r i u m c o n s t a n t s o f t h e i s o m e r s m u s t
n o t be e q u a l ,
2.
S,
the
ie.
Ko r t h o + Km e t a f Kp a r a
so lv a tin g m olecule,
must not c a p tu re
electro n s.
3.
S m u s t be a good s o l v a t o r o f n e g a t i v e io n s so
t h a t MS” a s w e l l a s M- i s o b s e r v a b l e .
4.
The s y s t e m
m u st be in e q u i l i b r i u m
so t h a t
Kg [S] = [MS- ] / [ M - ] = CONSTANT.
5.
The m a s s s p e c t r o m e t e r m u s t a c c u r a t e l y m e a s u r e
[MS- ] / [ M - ] .
C o ndition
nitro b en zen es
met
by
#1
has
been
choosing
an
ap p ro p ria te
sp ectru m .
also
C o n d itio n
eq u ilib riu m .
type of
It
for
C onditions
so lv en t,
su b stitu ted
#2 a n d
m o lecu le
#3 a r e
such
as
value
to g iv e observable s ig n a ls
f o r both
g ive
sta te s
W h e th e r o r not. t h i s
io n iz a tio n system
tru e
larg e
m ust n o t
#4
be
th a t has a s u f f ic ie n tly
the an aly te o f i n t e r e s t
M- a n d MS- .
to
as d e sc rib e d p re v io u sly .
d i m e t h y l s u l f o x i d e (DMSO),
w ith
shown
th at
a sig n ifican t
the
is tru e
;
background
system
m ust
be
in
w i l l d e p e n d on w h a t
i s c h o s e n t o work w i t h .
;
Two p o s s i b l e
i
• I
c h o i c e s a r e n e g a t i v e c h e m i c a l i o n i z a t i o n (NCI) a n d a t m o s p h e r i c
pressure
i o n i z a t i o n (API).
I
By a n a l y z i n g t h e c h e m i c a l d y n a m i c s o f
th e r e a c t i o n s in b o th s y s te m s , one o f th e s e tu r n s o u t to be th e
.
more l i k e l y system
p lace.
I
I
1
\
'i
in w hich th e s o l v a t i n g e q u i lib r i u m
w ill take
;
i
I
;
I'
)i
5
C o n d i t i o n #5 r e q u i r e s
m easures
the
co n d itio n
through
ratio ,
R,
t h a t t h e mass s p e c t r o m e t e r a c c u r a t e l y
of
may b e d i f f i c u l t
th e
apertu re
in to
[MS- ] / [ M - ]
to m eet,
the
m ass
as
in
th e
th e
source.
T his
tra n sp o rt of
an aly zin g
reg io n
ions
may b e
a c c o m p a n i e d b y c o l l i s i o n s w h i c h c o u l d d i s s o c i a t e MS- . 2
in th e
APIMS e x t r e m e p r e s s u r e a n d t e m p e r a t u r e g r a d i e n t s e x i s t
in th e
region of the a p e rtu re
w h i c h , may a l s o a l t e r
the a c tu a l value o f R th a t
is
in th e
source.
th e o b serv ed R from
6
STATEMENT OF THE PROBLEM
As s h o w n i n t h e
in tro d u ctio n ,
may b e p o s s i b l e u s i n g
a neutral
the
s o lv a tin g m olecule.
should have a c h a r a c t e r i s t i c r a t i o o f
d ifferen t
The
described
id e n tificatio n
of
isom ers
E ac h i s o m e r
[MS- ] / [ M - ] , s t e m m i n g f r o m a
Kf v a l u e .
purpose
in the
of
th is
research
in troduction
to see
is
if
to
explore
the
solvation
the
m ethod
eq u ilib ria
m e t h o d w o r k s a n d t h e t h e o r y h o l d s u n d e r c o n d i t i o n s o f a n a l y s i s by
GC/ECMS.
The e q u i l i b r i u m
com pared
to
achieved.
expected
If
th ere
b e tw e e n tw o
v alues
are
any
to
io n s w i l l be exam ined and
determ in e
d ev iatio n s
a t t e m p t w i l l b e m ad e t o e x p l a i n t h e m .
if
from
eq u ilib riu m
is
the
an
theory,
I
CHEMICAL DYNAMICS
The f o u r t h c o n d i t i o n n e c e s s a r y f o r d i s t i n g u i s h i n g
so lv atio n
eq u ilib ria,
th a t
of
req u irin g
i s o m e r s by
eq u ilib riu m ,
can
be
t h e o r e t i c a l l y e x a m in e d by p r e d i c t i n g t h e c h e m i c a l d y n a m ic s i n t h e
ion source.
reduce to
The e q u a t i o n s o b t a i n e d
Kj= [S]
=
[MS- ] / [ M “ ] ,
if
from t h e s e p r e d i c t i o n s s h o u ld
equilibrium
is
achieved
in
the
source.
The i o n a n d e l e c t r o n r e a c t i o n s
shown i n r e a c t i o n s
such
as
B and
reactio n s
5 - 1 2
P+ m ay
as w r itte n
below .
d iffer
occur
i n NCI a n d API a r e s i m i l a r a s
The i d e n t i t i e s
betw een
API
o f some s p e c i e s
and
f o r b o th m ethods.
NCI,
but
th e
A m ore d e t a i l e d
d e s c r i p t i o n o f h ow t h e NCI i o n i z a t i o n s o u r c e w o r k s i s g i v e n by.
H arriso n .3
T h e A P I s o u r c e i s d e s c r i b e d b y McKeown a n d S i e g e l . 4
The f o l l o w i n g
source.
r e a c t i o n s d e s c r i b e w hat i s happening w i t h i n e i t h e r
P+ m eans a n y p o s i t i v e
th e v o lu m e tric flow r a t e
of the source,
io n , th e r a te
co n stan t,
F/V , i s
t h r o u g h t h e s o u r c e d i v i d e d by t h e v o l u m e
and t h e d i f f u s i o n c o n s t a n t ,
DyZr0 3 ,
i s d e p e n d e n t on t h e g e o m e t r y o f t h e s o u r c e .
w i l l be g i v e n a n u m e r i c a l v a l u e l a t e r .
is a value th a t
T his r a t e c o n s ta n t
A ll of th e r a t e c o n s ta n ts
have been chosen to p r e s e n t th e m ost fa v o ra b le case.
8
Form ation R eactio n s
(5)
M + e —^M
ke c = 4 x 10 7 c c / s e c
(6)
M- + S + B - ^ M S - + B
k S0 I = 1 *
5
IO- 2 7 c c 3/ s e c
Loss R e a c tio n s
(7)
MS- + B—>M
+ S +
(8)
M- + P +---- > NEUTRALS
(9)
MS- +
(10)
e-
(ID
ALL i o n s ,
rad icals,
(12)
ALL i o n s ,
e t c . -----^DIFFUSION TO WALLS
B
—> NEUTRALS
R^ d e p e n d s on p r e s s u r e 3
t P+----- => NEUTRALS
From t h e
‘ R0 _ = 8 x IO- 7 c c / s e c
n e u t r a l s — >VENT
above e q u a t i o n s ,
3
k = F /V
k = D /r
an e x p r e s s io n
can be w r i t t e n
for
t h e p r o d u c t i o n o f MS- w i t h t i m e :
(13)
d [MS- ] / d t = k g o l
[M "][S][B]
- k _ s o l [MS- ] [B]
- Ri [MS~] [P+ ] -
The s t e a d y s t a t e
th is
approxim ation,
[F/V] [MS- ] -
d [ M S - ] / d t = 0,
[ D / r 0 2 ] [MS- ]
may b e a p p l i e d
f l o w - t h r o u g h r e a c t o r i n w h ic h m ix in g by d i f f u s i o n
more r a p i d
than v e n t i l a t i o n
through
13 e q u a l t o z e r o a n d r e a r r a n g i n g ,
the c e ll.
resu lts
S etting
in e q u a tio n
14:
to
i s much
equation
(14)
C ondition
[MS~]
[M I
k^ [ S ] [ B ]
k - s o l LB] +
____________ + F/V + W r 0 2
four s t a t e s :
(15)
E q u atio n
term s
=
14 c a n
[MS-1
[MT]
=
Kf [S]
reduce
to
eq u atio n
in th e d e n o m in a to r,
w ith resp ect to the f i r s t
15 o n l y
if
the
la st
th ree
R [P + ] + F/V + D / r 0 ^, a r e n e g l i g i b l e
term ,
k _ s o -L[B].
U s i n g t h e f o l l o w i n g t y p i c a l NCI v a l u e s f o r t h e p a r a m e t e r s
t h e d e n o m i n a t o r o f e q u a t i o n 14:
kg ol = I x
IO- 2 7 c c / s e c
[S ]
= 2 x 10-*•5 CC- "*• ( a t 0 . 1 T o r r )
[B]
= 2 x I O 16 c c - 1
= 6.4 x 1
0
(a t
2. T o r r )
cc/sec ®
[P+] = 3 x IOlO c c - "*F/V
D
= 100 s e c --*" ( l O O c c / s e c / c c )
= 1 00 c m 2 / s e c ( a t I T o r r ) ^
r 02
k_s o i
= 0.02 cm2
5
= 1.7 x 1 0 “ 12 c c / s e c
(The v a l u e
for
k_ g o 2 was c a l c u l a t e d
fro m Eq.
14
u s i n g t h e above v a l u e s and a s s u m in g an o b s e r v a b l e r a t i o
of
I.)
From t h e v a l u e s g i v e n :
k - s o l [B] = 3.4 x IO4
R [ P + ] + F /V + D / r 0 2 = 7.0 x IO 3.
in
10
The sum o f t h e l a s t t h r e e t e r m s o f t h e d e n o m i n a t o r ,
to r e c o m b i n a t i o n , v e n t i l a t i o n , and d i f f u s i o n
about
20 p e r c e n t
of
th e
first
term ,
w hich a r e due
resp ectiv ely ,
so n e g l i g i b i l i t y
is
is
not
proved.
U s i n g t h e maximum v a l u e
for
[S] u n d e r NCI c o n d i t i o n s
IO- 4 a t m . ) , an d a s s u m i n g a r e a s o n a b l e
maximum t h e o r e t i c a l r a t i o
[MS ] / [M- ] = Kf [S]
(1.3 x
v a l u e (500 a t m . - 1 ), t h e
i s o b t a i n e d f r o m e q u a t i o n 15:
= ( 5 0 0 a t m . 1 ) (1.3 x 10 * a t m . )
0.065
T h i s m a x i m u m s i g n a l f o r MS- i s l e s s t h a n I p e r c e n t t h a t o f M- ,
w h i c h w o u l d make MS" d i f f i c u l t
fu rth er
in c re a se d
fav o rab le
to
favor
io n iz a tio n
to
observe.
fo rm atio n
te ch n iq u e
for
of
Since
[S]
MS- ,
NCI
th is
ty p e
cannot
is
of
not
be
a
iso m e r
d istin ctio n .
The f o l l o w i n g
manner.
valu es
in
the
k - s o l h a s b e e n c a l c u l a t e d t h e s a m e way a s b e f o r e .
= 7 x IO- 1 1 c c / s e c
h-sol
= I x
k SOl
IO- 2 7 c c 2/ s e c
[B]
=
I x 10 1 ^ c c - 1
[S]
=
7 x 10 1 ^ c c - 1
Ri
=
I x 10
R /V
=
=
ro2
cc/sec
= 10® c c - 1
[P+ ]
D
f o r API c a n b e a p p l i e d
I s e c -1 (I c c /s e c
0.25 c m 2/ s e c
=
0.04 cm2
7
7
same
11
From t h e API v a l u e s :
k _ s o l [B]
= 7 x IO8
Ri [ P + ] + F / V + D / r 0 2 = 1 0 7 . 2 5
The
la st
n eg lig ib le
th ree
w ith
respect
com plete ex p ressio n
Kf [ S ] ,
term s
to
the
th e
for R to
deno m in ato r
first
term .
are
T his
r e d u c e t o e q u a t i o n 15,
d efin itely
enables
the
tMS“ ] / [ M “ ] =
w hich s u g g e s t s t h a t t h e s o l v a t i o n e q u i l i b r i a m ethod o f
isom er d i s t i n c t i o n
i n t h e API i s
The r e a s o n API i s
analy sis
order.
in
lies
p red icted
th e o re tic a lly possible.
t o s u r p a s s NCI f o r t h i s
in th e f a c t th a t th e s o lv a tio n r e a c tio n
The r a t e o f a t h i r d
(16)
R ate
order reactio n
type o f
is th ird
is ca lc u la te d
by :
= k s o l [M“ ] [ S ] [B].
S ince th e b u f f e r gas c o n c e n tr a ti o n is c lo s e to th r e e o rd e rs
m a g n i t u d e h i g h e r i n A PI t h a n NCI, t h e r a t e o f r e a c t i o n
of
i s much
f a s t e r i n A P I . T h i s r a t e i s 7 x I O 8 [M- ] c o m p a r e d t o t h e NCI r a t e
of
4 x
I O ^ [M- ] .
A lso ,
th e
m o l e c u l e c a n b e made h i g h e r
of
the so lv atin g
co n cen tratio n
i n API,
fu rth er
of
th e
increasing
so lv atin g
the
rate
reaction.
U sing-an e a s i l y
achieved value of
Kf o f 5 0 0 , t h e c a l c u l a t e d R w o u l d b e 2 . 5 .
e a s ily o b serv ab le r a ti o of sig n a ls.
[S],
5 x 10- 3 atm ., and a
T h is w ould p r o v id e an
Thus, a c c o r d in g to th e o ry
u n d e r r e a s o n a b l e o p e r a t i n g c o n d i t i o n s , t h e API s o u r c e s h o u l d w o r k
f o r t h i s m ethod o f is o m e r d i s t i n c t i o n .
12
EXPERIMENTAL
The
in stru m en t
used
in
th is
h o m e —b u i l t m a s s s p e c t r o m e t e r .
research
was a s p e c i a l i z e d ,
The s o u r c e was a n a t m o s p h e r i c
p r e s s u r e i o n i z a t i o n s o u r c e t h a t c o u l d a l s o b e u s e d a s a n ECD o r a
corona d isch arg e so u rce.
w i l l be g iv e n l a t e r .
A d e ta ile d d e s c r ip tio n of th e source
To i n t r o d u c e s a m p l e s i n t o t h e s o u r c e , a g a s
c h r o m a t o g r a p h was u s e d w i t h
n itro g en
was p a s s e d
p rio r to en terin g
The g a s
the
n itro g e n as th e c a r r i e r gas.
through
o x y g e n a n d w a t e r —r e m o v i n g t r a p s
column.
ch ro m ato g rap h
was
a Gow-Mac m o d e l
750 t h a t
m o d i f i e d t o a c c o m m o d a te a H e w l e t t P a c k a r d 530 m i c r o m e t e r ,
m e t e r m a c ro b o re colum n (num ber 19095Z-121).
was i n s t a l l e d
in to
to red u ce th e
th e source.
steel,
heated,
The
was
10
The m a c r o b o r e c o l u m n
am ount o f colum n b l e e d
in tro d u ced
The c o lu m n was t h r e a d e d th r o u g h a s t a i n l e s s
t r a n s f e r l i n e and fed d i r e c t l y
in to the source.
The n e t r e s u l t w as t h a t t h e c o l u m n e n d e d a p p r o x i m a t e l y f l u s h w i t h
the entrance
in to
the
source.
Two m e t h o d s w e r e u s e d t o
in to the source.
larg e,
airtig h t
T he f i r s t
volum e,
in tro d u ce th e s o lv e n t m o lecu les
one was v i a a d i l u t e r ,
w ith make-up gas flo w in g
i n t o t h e s o u r c e t o m i x w i t h t h e GC e f f l u e n t .
w h ic h was a
through
it
and
The d i l u t i o n v o l u m e
h a s a s e p t u m p o r t w h i c h a l l o w s t h e i n j e c t i o n o f a known q u a n t i t y
of so lv atin g
c o m po u nd i n t o
the d ilu te r .
t h e m a k e -u p g a s and some i s c a r r i e d
This
is
then d ilu te d
in to the source.
by
Kno wing t h e
13
flo w r a t e th ro u g h th e d i l u t e r , th e t o t a l flow r a t e
source,
the
d ilu ter
(w hich
so lv atin g
volum e
in
of
the
m ost
m o lecu le
d ilu ter,
cases
is
in jecte d ,
the
pressure
atm o sp h eric),
and
the
through th e
tim e
in sid e
th e
from
the
am ount o f
the
in itia l
i n j e c t i o n , th e c o n c e n tr a ti o n of th e s o lv a tin g m o le c u le s in th e
s o u r c e can be c a l c u l a t e d .
The a m o u n t f l o w i n g o u t o f t h e d i l u t e r
a t any t i m e c a n be c a l c u l a t e d
the vo lu m etric
th e
d ilu te r
flow r a t e
and
t
is
m o lecu le
tim e
Once C i s
in th e s o u rc e
C = C0 e ~ ( p Zv ^t , w h e r e F i s
through th e d i l u t e r ,
the
s o lv a tin g m o lecu le.
from :
is:
elapsed
found,
V is
sin ce
t h e volume o f
in jectio n
of
the
th e amount of s o l v a t i n g
Cs = C ( F d / F t ) , w h e r e F d i s t h e f l o w
r a t e t h r o u g h t h e d i l u t e r a n d F fc
is th e t o t a l
flow r a t e of b o th
t h e colum n and t h e m a k e-u p g a s t h r o u g h t h e s o u r c e .
A disadvantage
of
th is
S, t h e s o l v a t i n g c o m p o u n d , i s
system
is
th at
the
co ncentration
a l w a y s c h a n g in g due t o t h e c o n s t a n t
flo w o f m ake-up gas i n t o and o u t o f t h e d i l u t e r .
days
to
co m p letely
p rep aratio n
clean
th e
d ilu ter
f o r a d i f f e r e n t one.
choice of so lv a tin g
of
com pounds i s
have s u f f i c i e n t vapor p re s s u re
to
of
A lso,
one
it
takes
so lv ato r
A nother problem
is
th at
in
the
l i m i t e d b eca u se th e y have to
ev ap o rate
in to
the
d ilu ter.
A n o th e r sy ste m was d e v i s e d to a l l e v i a t e th e s e d raw b ack s o f th e
d ilu terI
The s e c o n d
system
of these co n stru cted
diam eter,
t e s t e d was c a l l e d a " b u b b le r" .
w as a s i m p l e
cy lin d rical
tube,
The f i r s t
one
inch
in
w i t h a o n e - q u a r t e r in c h g l a s s tu b e t h a t was drawn t o a
f in e opening in s id e th e l a r g e r c y lin d e r .
T h i s was t h e m a k e - u p
14
gas
in let.
W ith
the
bubbler
filled
w ith
a su fficien t
amount o f
s o l v a t i n g c o m p o u n d , n i t r o g e n was b u b b l e d t h r o u g h t h e l i q u i d t o
s a tu r a t e th e gas w ith the s o lv a tin g
liq u id .
was t h e n a l l o w e d o u t v i a a g l a s s e x i t p o r t
top of th e
large
cylinder.
See F i g u r e
The s a t u r a t e d g a s
in th e
sid e,
near the
I.
3.5 inches
v
Figure
W ith
efficien cy
th e
I.
above d e s ig n ,
of s a tu ra tio n
designed to e lim in a te
sh o w n i n F i g u r e
2.
F i r s t Bubbler.
th e re
was some q u e s t i o n
as to th e
of th e make-up gas.
A n o t h e r b u b b l e r was
t h i s p o s s i b l e problem .
The b a s i c d e s i g n i s
10.5 inches
F i g u r e 2.
The
Second B u b b le r.
d i f f e r e n c e s a re changes
i n d i m e n s i o n a n d t h e u s e o f an
LC c o l u m n e n d w h i c h h a s a s i n t e r e d
g lass
frit
on t h e end.
The
s in te re d g lass
form s s m a lle r b u b b le s th an th e o r i g i n a l d esig n .
These
b u b b les
sm aller
produced
to
a
in
the
d iam eter
o rig in al
are
more
design.
easily
satu rated
The d i m e n s i o n s
of one and one h a l f
inches
to
th an
were
th o se
increased
accom m odate
th e
16
larg er
bu b b ler
tube.
The
heig h t
was
also
increased
so
the
v e r t i c a l d i s t a n c e t r a v e r s e d by t h e b u b b l e s was l o n g e r , i n c r e a s i n g
th e chance of s a tu ra tin g
dim ensions
re su lts
the
comes t h e
in crease
W ith an i n c r e a s e in t h e
o f volum e.
T his
l a r g e r volum e
in a l a r g e r s o lv e n t c a p a c ity , e n a b lin g a lo n g e r use as
b u b b ler
shown
th e b u bbles.
w ill
la te r,
d ifference
n e e d t o be r e f i l l e d
th e
in the
tw o
d ifferen t
resu lts.
le ss
d esig n s
Therefore,
o ften .
of
As w i l l
bub b lers
satu ratio n
of
the
be
made no
nitrogen
g a s a p p e a r e d t o be a c h i e v e d i n b o th c a s e s .
Once t h e a n a l y t e a n d t h e
resp ectiv e
gas li n e s ,
so lv ato r
m o lecu les
are
in t h e i r
t h e y a r e c o m b i n e d i n t h e s o u r c e o f t h e API.
T h e s o u r c e i s a h o m e m a d e e l e c t r o n c a p t u r e d e t e c t o r (ECD) w h i c h
co n sists
and
is
o f a volum e o f a b o u t
b o lted
onto
th e
I cm^ w i t h a g a s i n l e t a n d o u t l e t ,
front
q u a d r u p o l e s as shown in F i g u r e
platinum c y lin d e r
of
3.
the
vacuum
envelope
of
th e
T h is volum e i s
lin e d w ith a
i m b e d d e d w i t h 9 mCi o f n i c k e l 6 3.
The a p e r t u r e
o f t h e s o u r c e l e a d i n g t o t h e v acu um e n v e l o p e a n d m a s s a n a l y z e r i s
in a 5/8 in c h d ia m e te r d is k o f n ic k e l,
The
aperture
stain less
serve
is
20
m icrons
in
w hich i s
d iam eter.
s t e e l p i n m ounted c o a x i a l l y
in th e
25 m i c r o n s t h i c k .
There
source
a s a c o r o n a d i s c h a r g e o r a s t h e a n o d e o f a n ECD.
is
also
a
w hich can
gas out
heater
well
Ni foil
/ g o l d O-ring
aperture
g a s in
□
•
i cm
F i g u r e 3.
BCD S o u r c e o f Mass S p e c t r o m e t e r w i t h F r o n t F l a n g e
o f Vacuum E n v e l o p e .
The m ass a n a l y z e r i t s e l f
N uclear,
i s a g u a d r u p o l e d e s i g n by E x t r a -
Model 1 6 2 - 8 , c a p a b l e o f b e t t e r
u p t o a m a s s o f 500.
m u ltip lier
by G a l i l e o
ratem eter
(O rtec
The d e t e c t o r
i s a c h a n n e l t r o n 40 39 e l e c t r o n
E lectro-O ptics.
M odel
441)
is
th a n u n i t mass r e s o l u t i o n
The a n a l o g
recorded
F ig u re 4 shows a b lo c k diagram of th e s e tu p .
signal
by a c h a r t
from
a
recorder.
18
C hart
R ecorder
Rate
M eter
Bubbler
Mass
Source Analyser
F igure
T his
sin g le
mass
and
4.
Block D iagram o f I n s t r u m e n t .
sp ectro m eter
to tal
ion m o n ito rin g ,
developed
esp ecially
th e
ion m o n ito r,
dual
can
for
th is
o r DIM.
perform
m ass
sp ectra
and one more f u n c t i o n
pro ject.
This
la tter
colum n.
lik e
is
in o rd e r to
f r o m t h e G.C.
Once e v e r y t i m e i n t e r v a l , s u c h a s o n e s e c o n d , t h e m a s s
analyzer s e le c ts
signal
t h a t w as
function
T h i s was n e c e s s a r y
m o n i t o r tw o d i f f e r e n t io n s as one com pound e l u t e s
scans,
to
the reco rd er.
F ig u re
in teg rated
first
5.
The
c irc u its:
s w i t c h AD7512DKN.
one,
an d t h e n
the o th e r
The n e t r e s u l t
is
io n and s e n d s t h e
a p rin to u t
circ u it
was
made
w ith
3140 op
amps
and an
th e
t h a t looks
fo llo w in g
in teg rate d
c irc u it
The o t h e r c o m p o n e n t s w e r e t w o m a n u a l s w i t c h e s .
19
a sm all, red li g h t,
capacitors.
and v a r io u s r e s i s t o r s ,
F ig u re 6 shows th e
F igure
5.
resu ltin g
variable re s is to rs
circu it.
S a m p l e o f DIM P r i n t o u t .
and
20
^W NA
10K
F i g u r e 6.
DIM C i r c u i t .
(to MS)
21
The c o m p o u n d s u s e d w e r e p a r a - c y a n o n i t r o b e n z e n e (p-CNNB),
o rth o -,
m e ta
m eta-,
and
a n d p a r a - f l u o r o n i t r o b e n z e n e ( o , m, a n d p - F N B ),
p a ra -n itro a n iso le
triflu o ro n itro to lu en e
(m
( Itv-CF3 NB) ,
and
o rth o -,
P -O C H 3N B),
m e ta-,
and
m-
para-
d i n i t r o b e n z e n e ( 0 , m, a n d p - d i N B ) , a n d o r t h o - , m e t a - , a n d p a r a n i t r o t o l u e n e (0 , m, a n d p - N T ) .
A ld r ic h C hem ical
The a n a l y t e s w e r e o b t a i n e d f r o m
in 9 9+ % p u r i t y .
d o n e on t h e a n a l y t e s .
No f u r t h e r p u r i f i c a t i o n
The s o l v a t i n g m o l e c u l e ,
(DMSO), c a m e f r o m B a k e r a n d w a s d i s t i l l e d
s o lv e n t, benzene,
was r e a g e n t g r a d e
was
d im ethylsulfoxide
p r i o r to use.
from Baker.
The o n e
T h i s was n o t
f u r th e r p u rified .
T h e s a m p l e s u s e d w e r e mad e u p i n b e n z e n e t o a c o n c e n t r a t i o n
o f 5 t o 30 n g / m i c r o l i t e r .
into a d ilu te r,
in to
th e
u sed i n p l a c e o f t h e column,
source
in tro d u ced
Gaseous s a m p l e s were i n j e c t e d d i r e c t l y
w ith
in to
th e
the
carrier
source,
gas.
b oth
and a llo w e d to flow
Once t h e
th e
M-
and
sam ples
MS-
ions
w ere
w ere
m onitored.
To d e t e r m i n e t h e
to
see
v ario u s
if
v a lu e s of th e s o lv a tin g r e a c tio n s , and
eq u ilib riu m
sets
of d ata
is
in d eed
achieved
w ere c o lle c te d .
k n o w i n g t h e c o n c e n t r a t i o n o f S,
in
th e
M o n ito rin g
API
source,
M“ , MS” a n d
the experim ental value of
can
be calcu lated .
D a t a was c o l l e c t e d
f o r p l o t s o f Kf v s .
m a n i p u l a t i o n s o f t h a t d a t a s u c h a s 1/K v s .
1 /R v s . I / [ S ].
T h e r e a s o n t h e Kf v s .
[S] a n d v a r i o u s o t h e r
[S ], In K vs.
[S],
and
[S] d a t a w a s c o l l e c t e d w a s
22
t o c h e c k t h e c o n s t a n c y o f Kf o v e r v a r i o u s c o n c e n t r a t i o n s o f t h e
solyator.
The
te m p eratu re
p late.
th e
S
of a w ater bath
A fo il
in lets
co n ce n tratio n
was
v arie d
co n tain in g
by
raisin g
the b u b b le r v ia
th e
a hot
I id was s e c u r e d o v e r th e to p o f t h e b a th a ro u n d
and o u t l e t s
to
th e
bub b ler to
keep th e h e a t
in
and
reduce e v a p o ra tio n of th e w a te r bath.
H eating ta p e w a s ,c o ile d
around the gas l i n e
and w rapped a l l
leav in g the bubbler,
along i t to th e so u rce.
a hig h er tem p eratu re
of th e
so lv atin g
way
C a re was ta k e n t o k e e p t h i s g a s l i n e a t
than th e
m o lecu le
w ater bath to prevent condensation
in th e
lin e.
c o n c e n t r a t i o n o f S c a n be c a l c u l a t e d
and e a s i l y
the
W ith t h i s
to a f a ir l y
set-u p ,
reliab le
th e
value,
controlled.
The m o n i t o r i n g
of
M“ a n d
MS-
com pletes
th e
experim ent.
S e v e r a l d i f f e r e n t m e t h o d s o f m o n i t o r i n g M~, MS- a n d R w e r e u s e d ,
first
scan n in g ,
th en s in g le
d u a l ion m o n ito r in g
(DIM).
ion m o n ito rin g
(SIM ),
and f i n a l l y
23
CALCULATION OF EXPECTED Kf VALUES
The o r i g i n a l i n s t r u m e n t u s e d a d i l u t e r i n t h e m a k e - u p g a s
lin e
to
colum n
d eliv er
was u s e d
the
to
p relim in ary d ata
w as
so lv atin g
in tro d u ce
retriev ed
m o lecu le
the
to
to
an aly te.
see
if
th e
source,
W ith
th is
and
a
set-u p ,
t h i s p r o j e c t w as w o r t h
pursuing.
The t w o s o l v a t i n g
compounds checked
w e r e DMSO a n d
m ethanol.
T h e s e w e r e c h o s e n b e c a u s e t h e r e a r e k n o w n Kf v a l u e s
f o r t h e s e compounds w i t h v a r i o u s s u b s t i t u t e d b e n z e n e s such as t h e
f lu o r o n i trobenzenes,. n i t r o to lu e n e s ,
The
known
U nfortunately,
Kf
values
n itro an ilin es
were
all
and o t h e r s . ^
obtained
at
7 0°C.
t h e compounds u sed r e q u i r e a column t e m p e r a t u r e o f
a r o u n d 7 O0 C,, s o t h e s o l v a t i n g d a t a f r o m . t h i s s e t - u p m u s t be t a k e n
a t 125°C o r h i g h e r .
T h i s i s b e c a u s e t h e s o u r c e m u s t be k e p t a t
l e a s t 50° h i g h e r t h a n t h e
experim ental
Kf v a l u e s
incom ing gas.
at
150°C,
Kf I^O v a l u e s m u s t b e c a l c u l a t e d
to
In o r d e r t o
Kf K a t
150°,
compare t h e
th e
K eb arle
f r o m t h e 70 d e g r e e d a t a u s i n g t h e
g i v e n flH a n d fiS v a l u e s , a s s h o w n b e l o w :
l]G = - R T l n K f
AG = AH - TAS
For exam ple,
DMSO:
t o f i n d Kf a t
1 5 0 ° f o r t h e s o l v a t i o n o f m-CF^NB w i t h
24
= -7 .1
k cai/m o le, AH^
=
-1 4 .6
k cal/m o le,
AS70 = - 2 2 . 3 c a l / m o l e
150°C = 423°K
AG4 2 3 = - 1 4 . 6 -
(423) (-0 .0 2 2 3 )
AG423 = - 5 . 1 6 7 k c a l / m o l e
AG423 = -RTl nK
- 5 . 1 6 7 = - ( 1 . 9 8 7 x I O - 3 ) (4 23 ) l n K
KgK = 4 6 7 . 5 a t m . - 3
A ccording
to
K ebarle,
there
are
errors
in h i s
m easurem ents
f o r Ah a n d AS, 3 t h u s t h e K3 3 ^ c a n b e a p p r o x i m a t e d t o 5 0 0 a t m . - 3 .
A l l known Kj= v a l u e s u s e d
f o r c o m p a r i s o n w e r e c a l c u l a t e d up t o a n
e x p e r i m e n t a l t e m p e r a t u r e o f 150°C by t h i s m e t h o d .
i n T a b l e 2.
.
Table
Compound
They a r e l i s t e d
2.
C a l c u l a t e d V a l u e s o f Kj=
AH k c a l / m o l e
AS c a l / m o l e - d e g
Kj= a t m . - 3
P-OCH3NB
-1 6 .3
-2 2.5
320
Ki-CF3NB
-1 4 .6
-22 .3
468
p —CNNB
-16 .0
-33.6
8
25
Once t h e Kf v a l u e s a r e f o u n d ,
th e ra tio ,
MS- Z i n t e n s i t y M- c a n b e p r e d i c t e d .
equilibrium
T h i s co m e s d i r e c t l y
expression,
K4; = [MS ]
['M- ] [S]
w here:
R = [MS- ]
[M- ]
and
Kf [S]
Thus,
k n o w i n g Kf a n d
R, o f t h e I n t e n s i t y
=R
[ S ] > R may b e p r e d i c t e d .
from t h e
26
RESULTS
W ith th e o r i g i n a l d i l u t e e ,
to
find
[S], th e
tem perature of
t h e r oo m m u s t be known i n o r d e r t o g e t t h e v a p o r p r e s s u r e o f t h e
solvent.
Then t h e a p p r o p r i a t e volum e o f s o l v e n t m o l e c u l e can be
in jected
so
exam ple, a t
as
not
to
leav e
any
liq u id
u n evaporated.
2 0°C t h e v a p o r p r e s s u r e o f DMSO i s
volum e o f t h e d i l u t e r
is
6 liters
For
5 x IO- ^ a t m .
The
and i s a t a t m o s p h e r i c p r e s s u r e .
To g e t t h e i n i t i a l c o n c e n t r a t i o n o f S , s t a r t w i t h t h e i d e a l g a s
la w and r e a r r a n g e
(20)
t o e q u a t i o n 20:
PV = n
RT
(5 x 1 0 _ ^ ) ( 6 L ) = n = 1 . 2 5 x 1 0 “ ^ m o l e s
(0.0821)(293)
(1 .2 5 x IO - ^ m o le s ) (78g/m ole) (lcc/1 .1 0 1 4 g )
=
= 8.83 x 1 0 " 3 c c
In jectin g
8.83
m icro liters
of
DM SO w o u l d
c o n c e n t r a t i o n p o s s i b l e a t 20°C>
give
the
maximum
0 . 3 8 t o r r (5 x 1 0 “ ^ a t m .
= 0.38
to rr).
P relim inary
the
so lv ato r,
experim ents,
done w ith th e d i l u t e r to in tro d u c e
showed t h a t s o l v a t i o n does
indeed o ccu r
s o u r c e , a n d i s o b s e r v a b l e a s shown in F i g u r e s 7 seen
from t h e s e
F igures,
th ere
is
a d efin ite
11 .
i n t h e API
As c a n b e
d ifferen ce
betw een
t h e b a c k g r o u n d i o n s w h e n e i t h e r MeOH o r DMSO i s p r e s e n t .
MeOH
I
27
t e n d s t o g i v e a l o t o f b a c k g r o u n d i o n s w i t h no a n a l y t e p r e s e n t ,
and e x tra n e o u s
See F ig u r e s
io n s,
ions
9 - 12.
analyte
DMSO g i v e s
passes
through
com paratively
r e s e a r c h , DMSO i s
o n l y com po u nd t h a t
An e x p e r i m e n t
that it
showed
io n
source
was r u n o n t h e NCIMS t o
th at
solv atio n
no s o l v a t i o n
pressure.
1% o f
S ince
can
exp ected R t h a t
shows
ions,
the
for
of
is
M” o c c u r s
p red icted
scan,
For a value t h a t
d rastically .
to
f o r R and th e
R for th is
nitrobenzene.
w a s 10% o f t h e
sig n ifican t
o f m e t h a n o l much
■
■
■
ion so u rce p re s s u re .
191 a n d 269 m a s s u n i t s ,
first
.
pressure
in
t h e API,
be m e a su re d and com pared t o
v alues
The p r e d i c t e d
the
the t o t a l
so lv atio n
[MS""]/[M“ ] ,
for the
fo r isom er i d e n t i f i c a t i o n .
In API e x p e r i m e n t s ,
■■
than
Thus,
check t h e assu m p tio n
occurred
s o lv a tio n ta k e s p la c e w ith the p a r t i a l
less
background
t h e b e t t e r s o l v a t o r and i s t h e
The p a r t i a l p r e s s u r e o f m e t h a n o l , t h e s o l v a t o r ,
to tal
source.
w i l l be u s e d i n t h a t c a p a c i t y .
would n o t f a c i l i t a t e
resu lts
the
little
a n d no e x t r a n e o u s i o n s d u r i n g t h e s o l v a t i o n .
purposes o f . t h i s
T he
whe n t h e
be a c o n s t a n t
in ten sities
the
th e
ratio ,
calcu lated ,
value.
of th e
R =
T able
3
M- a n d MS-
f o r t h e s y s t e m o f m-CFgNB a n d DMSO.
experim ent
but s ig n ific a n tly
is
0.26,
d ifferen t
i s p r e d i c t e d to be c o n s ta n t,
reasonably close
for
the
other
to
scans.
R a p p e a r s to change
28
W/O
F ig u re
7.
DMSO
Ion
scan
With DMSO
o f m-CF^NB a n d
m olecular ion,
DM SO.
269 i s
191 i s t h e m o l e c u l a r i o n .
the
so lv ated
29
W /O MeOH
With MeOH
191
223
269
F i g u r e 8.
I o n s c a n o f m-CFgNB a n d MeOH.
ion,
223
is
th e
so lv ated
ion,
191 i s t h e m o l e c u l a r
and
269
is
s o l v a t e d by t h e r e m a i n i n g DMSO i n d i l u t e r .
M-
30
With Mg OH
W/O IVIcOH
F i g u r e 9.
I o n s c a n o f o-NT w i t h a n d w i t h o u t MeOH.
MS- i s
10.
137,
16 9.
W/O MgOH
Figure
M- i s
With MgOH
I o n s c a n o f m-NT w i t h
MS- i s
and w i t h o u t
169.
MeOH.
M
is
13 7,
31
W/O MeOH
With MeOH
137
137
. I
F igure
11.
I o n s c a n o f p-NT w i t h a n d w i t h o u t Me OH.
MS-
is
12.
M
is
137,
DMSO
Bkgd
MeOH B a c k g r o u n d ,
DMSO B a c k g r o u n d ,
_
169.
MeOH
Bkgd
F igure
a
xlO ,
xlO,
resolution
reso lu tio n
1 5 0° C .
6,
6,
= 1 7 O0 C
=
32
T a b l e 3.
Ion I n t e n s i t i e s
a n d R V a l u e s f o r m-CF3N B / 0 . 38 t o r r EMSO
INTENSITY
MSM-
( 2 6 9)
(191)
R (269/191)
11.5
10.0
5.0
2.0
1.5
57.0
58.5
47.0
36.0
12.5
0.202
0.171
0.106
0.056
0.120
The i n e q u a l i t y o f o b s e r v e d and e x p e c te d v a l u e s
f o r R may b e
e x p l a i n e d by a p e r t u r e e f f e c t s .
In th e r e g io n o f th e a p e r t u r e ,
extrem e
tem p eratu re,
and
There is
an e x p a n s i o n r e g i o n on t h e
where
co llisio n s
can o ccu r
o f t h e MS^ c l u s t e r .
a p a r t t o M- ,
pressure
If
v elo city
ex it
sid e
w h i c h may r e s u l t
f
is
th e
a n d no M- i s d e s t r o y e d ,
of the
ex ist.
apertu re
in th e d i s s o c ia tio n
fractio n
of
MS-
th at
falls
t h e o b s e r v e d r a t i o would be
a fu n c tio n of th e r e a l r a t i o or the r e a l
ex p lain
g rad ien ts
value.
th e in e q u a lity o f th e observed r a t i o s ,
T his does n o t
however.
A p o s s ib le e x p la n a tio n fo r th e in e q u a lity of th e observed
ratio s
m asses,
is
th at
during
th e tim e betw een o b serv in g
t h e M- and MS-
the r a t i o rem ains c o n s ta n t, but the i n t e n s i t i e s
MS- c h a n g e a s t h e p e a k e l u t e s f r o m t h e c o l u m n .
sh ow p l o t s
of the
i n t e n s i t y o f an io n vs.
o f M- a n d
F i g u r e s 13 a n d 14
scan num ber,
revealing
t h a t t h e M- a n d MS- c o n c e n t r a t i o n s d e f i n i t e l y a p p e a r t o c h a n g e a t
d ifferen t
rates.
T h i s c o u l d be a n a r t i f a c t
of the
tim e
it
tak es
33
to
scan
mass
from
M- t o
MS- .
sp ectro m eter,
seconds.
During
may c h a n g e ,
a
th at
the e le c tr o n
of
M-
change
tim e,
alterin g
co n cen tratio n
Even a t
the
has
capture
of
t h e f a s t e s t s c a n r a t e on t h e
78
m ass
u n its
th e concentration of
observed
in ten sity
changed a c c o rd in g
of
to
tak es
M in
MS- ,
the
I
to
2
the source
because th e
equilibrium
of
reaction.
T h i s p h e n o m e n a i s a l s o o b s e r v e d f o r o t h e r c o m p o u n d s a s shown
in T ables 4 - 6 .
D esp ite th e se d is c r e p a n c ie s , th e p re lim in a ry
d a ta su g g e st t h a t t h i s system has prom ise.
Comparing th e a v e ra g e
R v a l u e s f r o m T a b l e s 4 - 6 t o e a c h o t h e r and s e e i n g
for
th ese
iso m ers
in creases,
so
does
th e
average
s u g g e s t s t h a t th e m ethod w o rk s, b u t t h a t th e d a t a
m e t h o d may b e c a u s i n g
t h e v a r i a t i o n o f R.
o f m e a s u r e m e n t m u s t be d e v i s e d .
A lso,
th at
Thus,
as
R v alues,
m easurem ent
a b e t t e r method
th e c o n c e n tr a tio n of S
s h o u l d be b e t t e r c o n t r o l l e d , t h u s t h e i n v e n t i o n o f t h e b u b b l e r
described p re v io u s ly .
O
A
O
A
SCAN NO.
F igure
13.
In te n sity vs.
S c a n Number f o r m-CFgNB/MeOH.
34
A
A
SCAN NO
F igure
14.
T a b l e 4.
Scan # :
In ten sity vs.
S c a n Number a n d R a t i o s
I
R a t i o MS- : 0.31
M
Ave. R :
Kf
S c a n Number f o r m-CF^NB/DMSO.
f o r o-diNB/MeOH
2
3
4
5
6
7
0.15
0.28
0.37
0.27
0.17
0.13
0.24
= I . 3 x 10^ a t m - 1
35
T a b l e 5.
Scan
# :/
S c a n Number a n d R a t i o s f o r m-diNB/MeOH
I
2
R a t i o MS" : 0 . 3 2
M
Ave. R :
Kf ^
0.36
3
4
0.36
0.30
5
6
0.18
I
0.24
0.18
0.26
= 2 . 5 x IO^ a t m " ^
T a b l e 6.
S c a n Number a n d R a t i o s f o r p-diNB/MeOH
Scan # :
I
2
3
4
5
6
7
R a t i o MS" : 0 . 0 6 4 0 . 0 6 7 0 . 1 2 5 0 . 1 0 7 0 092 0 . 0 6 3 0 . 0 5 3
M
Ave. R :
Kg
W ith
source
is
co n stan t.
d ilu ter,
0. 081
= 3 x iq I atm "1
the
b u b b ler
co n stan t,
if
set-u p ,
th e
co n cen tratio n
th e te m p e ra tu re of the
of
S in
the
b u b b le r rem ain s
T h e r e i s no e x p o n e n t i a l d i l u t i o n f a c t o r a s w i t h t h e
so an e x p e r i m e n t c a n be r e p e a t e d
at
d ifferen t
t h e day w i t h t h e same c o n c e n t r a t i o n o f S p r e s e n t ,
tim es
of
and thus o b ta in
id en tical r e s u lts .
S in c e th e p r e l i m i n a r y m ethod o f m e a su rin g th e r a t i o o f
to
[M~] w a s n o t r e l i a b l e , a n e w m e t h o d w a s d e v i s e d .
lo oking a t "in sta n ta n e o u s"
ratio s
from a sc a n ,
[MS"]
In stead of
th e to ta l ra tio
36
was loo k e d a t .
w ith a s in g le
T h i s was a c c o m p l i s h e d by m o n i t o r i n g f i r s t o n e i o n
in jectio n
of
sam ple
and t h e n
and m o n ito r th e o th e r ion of i n t e r e s t .
repeat
an d t h e r a t i o
calcu lated .
the
for
the
flu o ro n itrobenzenes
so lv ato r.
T able
and
sin g le
m-CFgNB,
o f t h e a r e a s was
ion m o n ito r t r a c e s
all
w ith
DMSO a s
T ab le 7 g i v e s th e a r e a s o f th e peaks and t h e i r r a t i o s .
The e x p e c t e d
0.19,
15 - 18 show
in jectio n
The a r e a s o f t h e p e a k s
were th e n found w ith a p l a n i m e t e r ,
F igures
the
R for
m-CFgNB s o l v a t e d
w ith
DMSO t u r n s
o u t t o be
w hich a g re e s w ith th e e x p e rim e n ta l value.
7.
Peak
A reas
Compound
and R a tio s
N itrobenzenes
AMS"
AM"
for
Some
[MS ] / [M
o-FNB
0.16
0. 24
0.67
m-FNB
0.07
0.12
0.57
p-FNB
0.13
0.17
0.79
m-CFgNB
1.14
0.22
0.19
F lu o rin ated
37
I
F ig u re
15.
S in g le Ion M o n ito r o f M
( 1 4 1 ) a n d MS
(219)
f o r o-FNB/DMSO.
219
F ig u re
16.
S in g le
I o n M o n i t o r o f M- ( 1 4 1 ) a n d MS
f o r m-FNB/DMSO.
(219)
38
219
F ig u re
17.
S in g le
Ion M o n ito r of M
( 1 4 1 ) a n d MS
(219)
I o n M o n i t o r o f M- ( 1 9 1 ) a n d MS
(269)
f o r p-FNB/DMSO.
F ig u re
18.
S in g le
f o r m-CFgNB/DMSO.
39
A b e t t e r s a m p l i n g mode was d e v e l o p e d t o m o n i t o r b o t h M” a n d
MS- d u r i n g t h e s a m e c h r o m a t o g r a p h i c p e a k .
both
the
ions
w ere m easured
circ u it
sectio n .
w ere
d escrib ed
id e n tica l
conditions.
p rev io u sly
in
th e
D etails
of
experim ental
A s a m p l e o f t h e d u a l i o n m o n i t o r (DIM) c h a r t r e c o r d w a s
a l s o shown p r e v i o u s l y
S ince th e re
m easurem ent,
speed,
under
T his would i n s u r e t h a t
ion
the
i n F i g u r e 5.
a r e many v a r i a b l e s
optim um
energy,
settin g s
co n cen tratio n
to a d ju st
for
of
i n o r d e r t o make a
reso lu tio n ,
an aly te,
DIM s a m p l i n g
and
o ld
or
n ew
b u b b ler,
w e r e o b t a i n e d by e x p e r i m e n t .
T able 8 g iv e s th e d a ta
obtained
f o r t h e s y s t e m p-CNNB/DMSO f o r
th e p u ls e and r e s o l u t i o n
experim ents.
varying
There
is
little
effect
on
the
ratio
caused
t h e p a r a m e t e r s o f p u l s e s p e e d and r e s o l u t i o n .
T a b l e 8.
R e s u l t s o f P u l s e and R e s o l u t i o n E x p e r i m e n t s f o r
p-CNNB/DMSO
P ulse
R esolution
R atio i
A
7.0
0.097
A
6.5
0.097
A
6.0
0.097
A
5.8
0.084
A
5.5
0.100
B
6.0
0.093
C
6. 0
0.095
A is
B is
C is
1.5 s e c . / p u l s e .
0.75 s e c . / p u l s e ,
2 sec./p u lse.
by
40
C o n cen tratio n
also
observed r a t i o of
CNNB/DM SO.
d iffe re n t
The
from
appears
to
have, l i t t l e
effect
on t h e
T a b le 9 shows th e d a t a o b t a i n e d f o r p p re d ic ted
th e
ra tio
observed
is
ratio
0 .002,
of
w h ich
0 .1 3 ,
is
q u ite
how ever
b o th
c o n c e n t r a t i o n s g a v e t h e same r a t i o .
T a b l e 9.
The
C o n c e n t r a t i o n E f f e c t on t h e R a t i o o f
C oncentration
A r e a MS-
A r e a M-
R
60; ng
0 .1 1 .
0.82
0 . 13
12 ng
0.66
5.08
0.13
ion
energy
(24 V) a n d h a l f
param eter
ion e n e rg y
was
checked
at
ion en erg y
The
v a l u e w as h i g h , a n d
was s i g n i f i c a n t s i g n a l f o r b o t h M- a n d MS-
in F ig u re
fu ll
(12V), u s i n g t h e " o l d " b u b b l e r .
s y s t e m u s e d w a s m-CFgNB/DMSO, b e c a u s e t h e
there
[MS- ]/[ M ~ ]
ions.
As s h o w n
1 9 , t h e f u l l i o n e n e r g y o f 24 v o l t s s h o u l d b e u s e d , a s
l e s s th a n f u l l e n e rg y d id n o t produce as s t r a i g h t a l i n e
p l o t o f InK v s . 1 / T d .
from a
41
I
1/T x IO3
F i g u r e 19.
Ln K v s .
1/T f o r V a r io u s Io n E n e r g i e s , and f o r
C a l c u l a t e d P o i n t s f r o m K e b a r l e 's D ata,
12 V o l t s
A
.
Q
.
24 V o l t s ,
Q
,
42
w ith
The two b u b b l e r s
w e r e c o m p a r e d by r e p e a t i n g
the
compounds,
same a n a l y t e
a n d p- O CH gN B) w i t h DMSO.
of
The
m e t a - and p a r a - n i t r o a n i s o l e
of
DMSO.
(m
v alu es a t a source tem perature
150°C w e re c o m p a r e d a g a i n s t t h e
pressure,
th e experim ent
The p a r t i a l
co n cen tratio n ,
pressure
or p a r tia l
o f DMSO w a s
calculated
by p l o t t i n g t h e M erck I n d e x v a l u e s on a g r a p h , d r a w i n g a c u r v e ,
and
th en
read in g
th e
experim ental tem peratures.
no s i g n i f i c a n t d i f f e r e n c e
co rresp o n d in g
pressures
As c a n be s e e n i n F i g u r e
in th e
v alu es obtained
from
th e
20 , t h e r e i s
from t h e two
bubblers.
The t e s t
m o n ito rin g
for
equilibrium
Kf e x P v s .
[S ] .
If
in th e
source
eq u ilib riu m
s h o u l d b e a c o n s t a n t v a l u e no m a t t e r w h a t
MS“ / M _ s h o u l d c h a n g e a s
[S] c h a n g e s .
[S]
w as a c c o m p l i s h e d by
is
achieved,
is.
This i s
Only t h e r a t i o
n ot th e
s h o w n i n F i g u r e 21 f o r p a r a - a n d m e t a - n i t r o a n i s o l e ,
f o r p a r a - c y a n o n i t r o b e n z e n e (p -CNNB).
t h e same s h a p e d c u r v e ,
b e t w e e n Kf a n d
[S].
Kf e x P
case
as
a n d F i g u r e 22
A ll t h r e e compounds have
s o t h e r e m u s t be some s o r t o f r e l a t i o n s h i p
43
F i g u r e 20.
C o m p a r i s o n o f Kf v s .
Improved
B ubblers.
[S ] f o r O r i g i n a l
K is atm
[S]
Q
i s atm.
and
44
[S ]x IO 3
F ig u r e 2 1 .
Kf v s .
[S]
K is
f o r p -OCH3NB, O
in atm- 1 ,
[S]
, and Hi-OCH3NB, A
i s in atm.
.
45
10 12
[S] x IO 3
F i g u r e 22.
vs.
[ S ] f o r p-CNNB.
atm.
14
16
K i s i n a t m - 1 , [S ] i s i n
46
O ne p o s s i b l e e x p l a n a t i o n i s t h e a p e r t u r e e f f e c t d e s c r i b e d
p rev io u sly .
into
In t h e
e x p a n sio n r e g io n th ro u g h w hich gas p a s s e s
th e e v a c u a te d , mass a n a ly z in g r e g io n , c o l l i s i o n s occur^ t h a t
rev erse the so lv a tio n process.
For exam ple:
MS" + N2------ + S + N2
T h is r e a c t i o n would re d u c e t h e o b s e rv e d i n t e n s i t y
a n d i n c r e a s e t h e i n t e n s i t y f o r M- b y a f r a c t i o n ,
in term s of th e
chem ical e q u i l i b r i a
happening,
fo r the
f.
i o n MS
W riting t h i s
a s s u m i n g M- d o e s
not d isso ciate:
(20)
Kexp
tF
t^
s
]
■ [MS- ] ^ = [MS- ] ^ - f [MS- ]
[M- ] 0
[M—] r + f [MS- ] r
(21)
(22)
K
= [MS- ]
[M- ] r Ts ]
(23)
[MS- ] r = Kr [ M "]r [S]
(24)
[MS- ] ^ = Kr TSl [M- ] - K [ S-I [M- :
[M- ] 0°
[M- ] r + Kr [M ] r [ S ] f
(25)
[MS- ] ^ = K „[ S ] - K „ [ S ] f
[M- ] q
I + Kr T s l f
= Kv. [S] ( I - f )
( I + Kr I S j f )
(26)
[MS- ] ^ = K
[M- I 0 TS]
(27)
(I - f )
( I + Kr [ S ] f )
(28)
kUsing t h i s
vs.
[S]
fin al
from
=
k- a
expression
ap p ro p ria tely
g r a p h i n F i g u r e 23 i s
^ c s 1I T
to g en e ra te a p re d ic te d
chosen
o btained,
values
for
plo t of
Ke x p
[ S ] a n d Kr , t h e
w hich c l o s e l y r e s e m b l e s
the data
47
p lo tted
earlier
in F ig u res
21 a n d 22.
28 i s a p o s s i b l e d e s c r i p t i o n
U nfortunately,
th e values fo r
relatio n sh ip .
equation
in g iv in g
compounds t e s t e d
(29)
enabling
expression
f and
are
not easily
A rearrangem ent
a lin ear
relatio n sh ip
of
th e
found
above
fo r a l l of the
by t h i s m e t h o d .
___1__
Kgxp
The s l o p e
th e
of the a p e rtu re e f f e c t .
w ith o u t a lin e a r
resulted
T herefore,
= [S]
f
- f)
U
is equal to f / ( l
the c a lc u la tio n
+
I
K f d - f)
- f) and th e i n t e r c e p t ,
o f f a n d Kr .
F igures
24 t o
1/K r ( I -
f),
26 show t h e
g r a p h s o b t a i n e d f r o m d a t a f o r m-OCHgNB, p-OCHgNB, p-CNNB, o-FNB, m-FNB
and
p-FNB.
values
T able
10 g i v e s
the
a r e a t 150°C e x c e p t p-CNNB,
p ertin en t
v alues.
A ll
Kr c a ^ c
w h i c h i s a t 225°C.
T a b le 10.
C o m p a r i s o n o f Kr c a ^c a n d K^ k f o r
Some F l u o r o n i t r o b e n z e n e s f r o m E q u a t i o n 29
Compound
C orr.
C o eff.
f
K calc
Kf*
m-OCHgNB
0.997
0.27
4628
—
p —OCH3NB
0.998
0.25
78 00
3200
p-CNNB
0.984
0.78
425
0.48
O-FNB
0.989
0.08
102
—
m-FNB
1.000
0.09
33,300
97,60
p-FNB
0.990
0.09
78,500.
161,000
48
8
F ig u re
23.
G enerated P lo t of K vs.
9
10
[S ] f r o m E q u a t i o n 29.
H e r e , K = 3000 a n d f = 0 . 1 0 .
49
[S] x 10
F i g u r e 24.
1/K e x p v s .
A
[ S ] f o r In-OCH3NB,
w i t h DMSO.
Td = 150°C
Q
a n d P - O C H 3NB,
50
[s]
F i g u r e 25.
x 10
V Ke xp v s * ^s I ^o r P - CNNB w i t h DMSO.
1 50°C.
K is
i n a t m - "*",
[S] i s
in atm.
Td
1/K
51
[s]x 10
F i g u r e 2 6.
1 / Ke xp v s *
^ ^o r ( ^ rom t o p t o b o t t o m ) o ,
a nd p-FNB w i t h DMSO.
[S]
= 1 5 0 o C.
i n atm.
K i n a t m - "*',
m,
52
The c o r r e l a t i o n
c o e f f i c i e n t was c a l c u l a t e d
re g re s s io n , program from S h a rp E l e c t r o n i c s
m o d e l EL-512 c a l c u l a t o r .
p o in ts
lie
co rrelatio n
on
th e
A value
lin e.
coefficien ts,
from a l i n e a r
C orp o ratio n
o f 1. 0 0 0 m e a n s a l l
As s e e n
1/Kg v s .
from
[S]
th e
is
on t h e i r
of the data
graphs
and
th e
a lin ear
relatio n sh ip
lead
th e
f o r t h e compounds t e s t e d .
T his
lin ear
calcu la ted
Kf
re la tio n sh ip
v alu e
when
r e la tio n s h ip j u s t discussed
(23)
a lin ear
not
com pared
to
to
K e b a r le 's ,
correct
so
th e
is not p e r f e c t l y ex p ressed as
___ 1_
Ke x p
O ther e x p re s s io n s
did
= [S]
f
+
I
Kr ( I
w e r e i n v e s t i g a t e d b e f o r e Eg.
r e l a t i o n s h i p betw een
[S]
a n d R o r K.
“
29 ,
searching
for
One o f t h e s e t h a t
showed p r o m is e was:
(30)
w hich
gave
tested .
a
I
R
lin e a r
= ___ I __________ 1_
■Kr ( l - f ) [S]
rela tio n
for
four
+
(I
out of
S e e F i g u r e s 27 t o 29 a n d T a b l e 1 1 .
f
-
f)
fiv e
compounds
A p p ly in g t h i s same
f o r m u l a t o t h e s o l v a t i o n o f t h e F N B 's b y t w o m o l e c u l e s o f DMSO
d id not r e s u l t
th a t
th e
in a l i n e a r r e l a t i o n s h i p .
system
suggests.
A lso,
sin ce
f o r p-CNNB, t h i s
th at
is
being
u ltim ately
for a ll
is
m ore
co m p licated
i t did not r e s u l t
F ig u re
than
31, s u g g e s t i n g
th is
ex p ressio n
in a l i n e a r r e l a t i o n s h i p
e x p re s s io n does n o t c o r r e c t l y d e s c r i b e th e system
stu d ied .
reach
equation
compounds t e s t e d .
F u rth er
29,
m an ip u latio n s
resu ltin g
in
lin ear
w ere
made
to
relatio n sh ip s
53
O
2-
x
U
/I
2H------- 1--------1--------1------- 1--------1------- 1--------1------- h
2
F i g u r e 27.
1/R v s .
6
10
i/s x ic r 2
14
16
I / [ S ] f o r ( f r o m t o p t o b o t t o m ) m-OCH^NB
and P-OCH3NB w i t h DMSO.
Td = 150°C.
[S]
i n atm.
54
F igure
28.
1/R v s .
I / [S ] f o r m-FNB,
DMSO.
Td = 70o C.
[S]
O
an d p-FNB, A
in atm.
with
55
I /[S] x IO"2
F i g u r e 2 9.
1/R v s .
1 /[S ]
225°C.
f o r p-CNNB w i t h DMSO.
[S]
in
atm .
I / R
56
-I---------- 1---------- 1----------1---------- 1---------- 1--------- 1---------- 1----------1—
4
8
12
16
20
1/[S]x IO"2
F ig u re
30 .
1/R
vs.
m o l e c u l e s o f DMSO.
I/[S]
for
so lv atio n
of
M-
by
M ( f r o m t o p t o b o t t o m ) i s o , m,
a n d p-FNB.
[S]
i n atm.
tw o
57
T ab le 11.
C o m p a r i s o n o f K^c a -*-0 a n d K^ k f o r
Some F l u o r i n a t e d N i t r o b e n z e n e s f r o m E q u a t i o n 30
Intercept
Slope
Compound
f
Kf
In-O C H 3 NB
5 .3 X IO"4
0.31
0.24
2700
P-OCH3NB
1.8 X IO"4
0.34
0.254
7285
3196
m-FNB
3 .5 X IO"5
0.10
0.093
34,800
97,600
p-FNB
I . 9 X IO"5
0.10
0.088
60,000
161,000
—
The b e s t e x p r e s s i o n w a s e q u a t i o n 2 9 , c o r r e l a t i n g
[S ] .
T h is
is
not
yet
exp erim en tal
Kf
H ow ever,
reference
th e
v alu es
th e
acc u rate
calcu la ted
Kf v a l u e s
degree as K ebarle ad m its to e r r o r s
ex p ressio n ,
do
not
may b e
in
appear
q u estio n
I / Kf a n d
a s . th e
co rrect.
to
some
in h i s
AH a n d AS v a l u e s w h i c h
w e r e u s e d t o c a l c u l a t e t h e r e f e r e n c e Kf ' s .
M ore c o m p o u n d s s h o u l d
be t e s t e d
it
ag ain st
o th er po ssib le
th is
ad d itio n s
th eo ry
to
v erify
or v a ria tio n s to it.
and
to
d eriv e
any
58
SUMMARY
A ccording
to
the
th e o re tic al
C h e m ic a l Dynamics s e c t i o n ,
i n t h e API s o u r c e .
seem s
to
show
equilibrium .
clo sely
th a t
th e
API
sig n als
what
happens
do
betw een
L eaving th e s o u rc e , t h e
an a p e r t u r e
len ses,
q u a d r u p o I e s and d e t e c t o r .
apertu re,
v elo city
vs.
not
in
th e
is achieved
[S] h o w e v e r ,
re fle c t
th is
T h i s c o n f l i c t o f t h e o r y a n d d a t a may b e r e s o l v e d by
through
the
done
therm odynam ic e q u i l i b r i u m
The p r e l i m i n a r y d a t a o f
exam in in g
d etecto r.
calcu latio n s
in to
th e re
gradients.
the
are
In
reg io n
As t h e i o n s ,
and
co n tain in g
etc.
te m p eratu re,
chaotic
w hich c o u ld b re a k a p a r t a s o l v a t e d
source
the
io n s and n e u t r a l s m u st p a s s
evacuated
extrem e
th is
the
zone,
ion,
p a s s through
pressure,
co llisio n s
MS- t o M .
the
and
can o ccu r
O ther t h i n g s
m a y h a p p e n , s u c h a s r e m o v i n g t h e e l e c t r o n f r o m M“ , m a k i n g i t a
n e u t r a l and u n o b s e rv a b le .
th e equilibrium ,
M" i o n s .
affectin g
T his
Ke x p = K„
eq u atio n
g en erated
f o r Kf v s .
above (eq.
[S].
afford
(I - f)
(I + K r (S ]f)
a curve
This s u g g e s ts
th a t
th at
resem bled
the
theory
the d ata
expressed
28) c l o s e l y d e s c r i b e s why t h e e x p e c t e d h o r i z o n t a l l i n e
f o r t h e g r a p h Kf v s .
not
t h e O b s e r v e d i n t e n s i t y o f t h e MS" a n d
One e x p r e s s i o n t h a t was e x a m i n e d was e q u a t i o n 28:
(28)
p lo tted
A l s o , t h e t e m p e r a t u r e c h a n g e may a l t e r
much
[S] i s n o t o b s e r v e d .
in fo rm atio n ,
and
do
S in c e c u r v e d l i n e s do
not
c learly
d efin e
a
59
relatio n sh ip ,
o th e r v ariatio n s
for a lin e a r re la tio n
On e
v aria tio n
resu lted
in
of equation
28 w e r e t r i e d ,
o f some s o r t b e t w e e n K^, o r R, a n d
d iscu ssed ,
straig h t
lin es
1/R
for
vs.
four
I/[S ]
com pounds
d o u b l e s o l v a t i o n o f M~ by. t w o m o l e c u l e s o f DMSO.
I
= [S]
f
(I -
Kexp
w hich gave
available
th e
lin e a r p lo ts
to use the
lin ear
or equal to
0.990.
line.
good
0.984.
An r
of
+
(m-OCHgNB,
in clu d in g the
This,
all
Krd "
f)
e q u a t i o n 29 ,
eq u ilib riu m
.
co efficien t,
for
Table
all
11 s h o w s t h a t
compounds
of the d ata p o in ts
com pounds.
T his
su p p o rts
th a t the ap ertu re causes a v a r ia tio n
cau sin g
i n c r e a s e o f M- t o
rr
was a b o v e
Four of th e s ix compounds had v a lu e s above
the
by
w as .
f o r e v e r y com pound t h a t had t h e d a t a
1.000 m eans a l l
of
then,
was e q u a t i o n ;
So t h e a g r e e m e n t o f d a t a t o t h e b e s t p o s s i b l e
for
p-
I_______
above r e l a t i o n s h i p .
co rrelatio n
30),
The r e l a t i o n s h i p t h a t g a v e t h e c l o s e s t
ap p are n t d e s c r ip tio n of the a p e rtu re e f f e c t s
(29)
[S].
(eq u atio n
OCHgNB, m-FNB a n d p - F N B ) b u t c u r v e s f o r t h e r e s t ,
not e sp e c ia lly u sefu l.
hoping
a
fractio n al
lo ss,
f,
a r e on t h e
lin e
th e
i s very
theory
of
in the observed
of
MS" a n d
an
(M"~ + fMS ).
A ls o , t h e v a l u e f i s n o t c o n s t a n t and v a r i e s fro m compound
t o compound.
The m a g n i t u d e o f f d o e s s e e m t o b e t i e d
v a l u e , a s s e e n i n T a b l e 11.
it
appears th a t
t o t h e Kf
K
F o r t h e f o u r Kf K v a l u e s a v a i l a b l e ,
a s Kf K i n c r e a s e s ,
b e c a u s e t h e l a r g e r t h e Kf K v a l u e ,
f decreases.
T h is makes s e n s e
t h e m ore s t a b l e t h e s o l v a t e d
60
i o n w o u ld be.
T h is s t r o n g e r s t a b i l i t y w ould re d u c e th e am ount
l o s t due t o c o l l i s i o n s ,
In
g en eral,
d istin ctio n
th e
shows
experim ents,
thus low ering the value of
so lv atio n
co n sid erab le
th e
ratio
in c re a s e d (T ables 4 - 6 )
th e
an aly tical
ap ertu re
rela tio n sh ip ,
values
of
the
of th is
s o u r c e and t h e o b s e r v e d
th e
as
m ethod a r e
isom er
p relim in ary
th e
value
So f a r ,
lim ite d .
stu d ied .
The
The f i n a l
d o e s n o t g i v e t h e e x p e c t e d Kf
N ev erth eless,
relatio n sh ip
In
of
fo r a g iven s e r i e s of is o m e rs.
e q u a t i o n 29, s t i l l
K ebarle.
m ethod
in creased
n eed t o be m ore c l o s e l y
o b ta in e d a re encouraging.
clarify
prom ise.
of
ap p licatio n s
effects
eq u ilib riu m
f.
the
lin ear
rela tio n sh ip s
A d d i t i o n a l work i s r e q u i r e d t o f u r t h e r
between th e
signals.
reactions
occurring
in
the
61
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