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Ionic Liquid Matrix-Enhanced Secondary Ion Mass Spectrometry: The Role of Proton
Transfer: Supporting Information
Jennifer J. Dertinger, Amy V. Walker*
Department of Materials Science and Engineering, RL 10, University of Texas at Dallas, 800 W.
Campbell Rd, Richardson, TX 75080
* Address reprint requests to Amy V. Walker, Department of Materials Science and Engineering, RL10, University
of Texas at Dallas, 800 W. Campbell Rd, Richardson, TX 75080; Ph: 972 883 5780; Fax: 972 883 5725; email:
O
CH3(CH2)13CH2 O O P
O
O
ON
O
O
CH3(CH2)13CH2
H
O
CD3(CD2)13CD2 O O P
O
O
ON
O
O
CD3(CD2)13CD2
H
O
CD3(CD2)13CD2 O O P
O
O
ON
O
O
CD3(CD2)13CD2
CD3
CD3
CD3
H
DD
DD
a)
b)
c)
DPPC
d62 DPPC
d75 DPPC
Figure 1. Structures of a) DPPC; b) d62 DPPC; and c) d75 DPPC.
HOCN
O
O
N
N
H
HOCN
O
O
N H
HOCN
O
O
N
N
H
HOCN
O
O
N
N
H
N
N
HN
N
H
OCN
O
O
HOCN
O
O
N
N
H
D
D
D
DD
D
a) MI CHCA
b) dMI CHCA
c) MI2 CHCA
d) EI CHCA
e) BI CHCA
f) trip CHCA
Figure 2. Structures of the ionic liquid matrices employed: a) MI CHCA; b) dMI CHCA; c) MI2
CHCA; d) EI CHCA; e) BI CHCA; and f) trip CHCA.
m/z, negative ions
187 188 189 190 191
norm
aliz
ed in
tens
ity
(CHCA - H)-
d62 DPPC
d75 DPPC
DPPC
Figure 3. SIMS spectra from m/z 187 to m/z 191 showing the (CHCA – H)- ion region for DPPC,
d62 DPPC and d75 DPPC in a MI2CHCA matrix. The spectra are normalized to the intensity of
(CHCA – H)- to make clear any changes in the (CHCA – H + 1)- and (CHCA – 2H + 2)- ion
intensities.
m/z, positive ions183 184 185 186 187
inte
nsity
(a.u
.)
d62 DPPC
(C5H15NPO4)+
(C5H14DNPO4)+
m/z, positive ions183 184 185 186 187
inte
nsity
(a.u
.)DPPC
(C5H15NPO4)+
a)
b)
Figure 4. TOF SIMS spectra centered at m/z 185 of DPPC and d62 DPPC in a MI CHCA matrix.
Matrix CationMI EI BI trip
I((ca
tion
+ D
)+ /I(ca
tion
+ H
)+
0.00
0.02
0.04
0.06
0.08
0.10Matrix Cation
MI EI BI trip
Enh
ance
men
t
0
2
4
6
8
10
12
14
16
DPPCd62 DPPC
a)
b)
Figure 5. a) Variation of secondary ion enhancements for the protonated molecular ion of DPPC
and d62 DPPC with matrix cation. b) Variation of the ratio of I((cation + D)+ to I(cation + H)+
with matrix cation using the analyte d62 DPPC.
Note: The molecular ion enhancements reported are lower for DPPC and d62 DPPC in these
experiments because the experiments were performed using a slightly different spin coating
conditions. In this case the concentration of DPPC and d62 DPPC were mixed with the ionic
liquid for slightly longer than 5 mins before spin coating (due to problems with the spin coater).
Reference Spectra for the Ionic Liquids Employed in this Study
All ionic liquids were characterized using 1H NMR spectroscopy, IR spectroscopy and TOF
SIMS. The spectra are shown below in the following order. For each ionic liquid the positive
mass spectrum will be first, followed by the negative mass spectrum, and the IR spectrum. On
the second page will be the 1H NMR spectra showing the proton shift. The ionic liquids are
ordered alphabetically by acronym.
BI CHCA
Figure 6. Positive and negative ion mass spectra and IR spectrum of BI CHCA.
Figure 7. 1H NMR spectrum of BI CHCA.
dMI CHCA
Figure 8. Positive and negative ion mass spectra and IR spectrum of dMI CHCA.
Figure 9. 1H NMR spectrum of dMI CHCA.
EI CHCA
Figure 10. Positive and negative ion mass spectra and IR spectrum of dMI CHCA.
Figure 11. 1H NMR spectrum of dMI CHCA.
MI CHCA
Figure 12. Positive and negative ion mass spectra and IR spectrum of MI CHCA.
Figure 13. 1H NMR spectrum of MI CHCA.
MI2CHCA
Figure 14. Positive and negative ion mass spectra and IR spectrum of MI2CHCA.
Figure 15. 1H NMR spectrum of MI2CHCA.
Trip CHCA
Figure 16. Positive and negative ion mass spectra and IR spectrum of trip CHCA.
Figure 17. 1H NMR spectrum of trip CHCA.