A Distonic Radical-Ion for Detection of Traces of Adventitious
Molecular Oxygen (O2) in Collision Gases used in Tandem Mass
Spectrometers
Freneil B. Jariwala, John A. Hibbs, Carl S. Weisbecker, John Ressler, Rahul L. Khade, Yong
Zhang, and Athula B. Attygalle*
*Center for Mass Spectrometry, Department of Chemistry, Chemical Biology and Biomedical
Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
Supplementary Material
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3
Supplementary Figures
Supplementary Figure 1. Pseudo-MS3 product-ion spectra of in-source-generated m/z 280 ion
acquired on a Waters Q-Tof API-US instrument using argon (99.998%) [collision energy: 1 eV]
(A), or nitrogen (generator) [collision energy: 1 eV] (B), as the collision gas. Spectra C, D, and
E depict a pseudo-MS3 product-ion spectra of in-source-generated m/z 280 ion acquired on a
Sciex API 2000 instrument using nitrogen (generator) as collision gas [collision energy: 5 eV]
(C), and on a Sciex API 4000 QqTrap instrument under two different acquisition modes [QqQ
MS/MS scan mode (D), and QqTrap time-delayed-fragment (TDF) scan mode (E)].
4
Supplementary Figure 2. Product-ion spectra of m/z 280 acquired on a Sciex API 3000 (A-E)
and Micromass Quattro Ultima (F-J) using a variety of collision gases and at low collision
energy (API 3000: 5 eV, Ultima: 1 eV).
5
Supplementary Figure 3. A magnified view of the spectrum from Figure 2E to illustrate the
peak at m/z 314 (representing the 16O–18O isotopologue adduct).
6
Supplementary Figure 4. (A) A stack plot representation of the product-ion spectra of massisolated m/z 280 ion acquired on a Sciex API 3000 instrument at various collision cell pressures,
using air as the collision gas. (B) A plot of mass spectral peak area ratio of m/z 312 and m/z 280
versus collision cell pressure for a variety of collision gases.
7
Supplementary Figure 5. High-resolution pseudo-MS3 product-ion spectrum of in-sourcegenerated m/z 280 ion acquired on a Thermo Fisher LTQ Orbitrap XL instrument in FT-mode
(Orbitrap) with helium (99.999%) as buffer gas.
8
Supplementary Figure 6. Plots of collision cell pressure versus the relative mass spectra peak
area ratios of m/z 312 and m/z 280 ions obtained using argon (99.998%) and nitrogen (99.998%)
(A), air (extra dry) and oxygen (99.993%) (B), and nitrogen (generator) as collision gas (C).
[Error bars, if not shown, are smaller than the displayed data symbols. The linear regression
equations are valid only for the linear regions as displayed.]
9
Supplementary Figure 7. Representative figure demonstrating how the oxygen content of
collision gases can be determined.
10
Supplementary Figure 8. Product-ion spectra (overlaid on top each other) of m/z 280 ion
acquired on a Sciex API 3000 instrument on eight separate occasions, using nitrogen (generator)
as collision gas and low collision energy setting of 5 eV.
11
Supplementary Figure 9. Computed structures for m/z 280 and 312 ions (red atoms represent
oxygen).
Theoretical Calculations
Geometry optimizations were done by using the density functional theory method
B3LYP1 with a 6-311++G(2d,2p) basis set for all atoms. Frequency analysis was done at
the same level to conform that the optimized structures are the minimum-energy states on
the respective potential energy surfaces. All calculations were performed using Gaussian
09.2
The formation of the m/z 312 species by the addition of molecular oxygen diradical to the
m/z 280 distonic radical cation was found to be a thermodynamically very favorable
process, due to a large negative reaction Gibbs free energy of -29.85 kcal/mol.
1) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652.
2) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.;
Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji,
H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.;
Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida,
M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, Jr., J. A.;
J. Peralta, E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.; Kudin, K. N.;
Staroverov, V. N.; Keith, T.; Kobayashi, R.; Normand,J.; Raghavachari, K.; Rendell, A.;
Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.;
Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann,
12
R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.;
Morokuma, K.; Zakrzewski,V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Dapprich, S.; Daniels, A. D.; Farkas, O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.;
Fox, D. J.; Gaussian 09, Revision B.01; Gaussian, Inc.: Wallingford CT, 2010.
Supplementary Tables
Supplementary Table 1. Minimum Purity of Nitrogen from the Generator*
Minimum
Flow at
Flow at
Flow at
Flow at
Flow at
Flow at
Flow at
Purity
60 psig
70 psig
80 psig
90 psig
100 psig
125 psig
145 psig
Percent N2
99.50
0.3
0.4
0.4
0.5
0.6
0.7
0.7
99.00
0.5
0.7
0.8
0.8
1.0
1.1
1.1
98.00
0.8
1.0
1.1
1.3
1.4
1.7
1.7
97.00
1.1
1.3
1.5
1.7
1.9
2.2
2.4
96.00
1.4
1.7
1.9
2.1
2.3
2.7
2.8
95.00
1.8
2.1
2.3
2.5
2.8
3.2
3.4
*Adapted from the specifications provided for Parker-Balston Model 75-A74 Nitrogen
Generation System.
13
Supplementary Table 2. Percent oxygen content in nitrogen from a
generator, determined by mass spectrometric and gas sensor methods.
Mass Spectrometric
Oxygen Gas Sensor
Date
Method
Method
09/09/13
5.2%
10/07/13
1.3%
10/23/13
4.6%
11/14/13
5.3%
11/30/13
3.1%
12/17/13
2.1%
01/17/14
2.4%
2.5%
02/07/14
4.3%
4.2%
14