Oxyhalide determination by ion chromatography-mass spectrometry

1. Oxyhalide determination by ion
chromatography-mass spectrometry
Dr. Elizabeth Gilchrist
elizabeth.gilchrist@ucc.ie
14th April 2016
CASi 2016

2. Outline
 Oxyhalides
 Considerations of coupling IC-MS
 Solvent addition method
 Direct coupling method

3. Oxyhalides
 Oxyhalides are commonly encountered in a range of
analytical applications
 Environmental e.g. soil, water, snow
 Forensic e.g. explosives
 Food/beverage quality e.g. rice, milk, water
 Several oxyhalides, namely perchlorate (ClO4
-) and
bromate (BrO3
-), can have an impact on health and
ecosystems
 It is important to monitor their concentrations in
sample matrices related to these areas

4. IC

5. • Ion Interaction Chromatography-Mass Spectrometry (IIC-MS)
• Chelation-based IC-MS (CIC-MS)
• IC-Inductively Coupled Plasma Mass Spectrometry (IC-ICP-MS)
• Suppressed (& Non-Suppressed) Ion Exchange
Chromatography-Mass Spectrometry (IEC-MS)
Modes of coupling IC-MS

6. IEC-ESI-MS is arguably most utilised mode
• Post-column/suppressor organic solvent addition
• Direct coupling – organic solvent pre-separation
Coupling IEC to MS

7. • Flow rate
• lower flow rates are generally required for compatibility with ESI (~0.1-0.7
mL/min)
• too low a flow rate for the separation increases band broadening
• Eluent compatibility
• suitably volatile solvent needed for trace analysis with ESI i.e. MeOH, MeCN
• eluting ion OH-/CO3
2-/MSA
• Sources of post-suppressor backpressure
• The ionisation source, flow diverter valves (if used), as well as any
supplementary solvent introduction generate backpressures
• Particularly important for membrane suppressors
Considerations: IEC-ESI-MS

8.  Membrane suppressors
prone to leakage at high P,
especially when coupling CD
and MS in series
 Typically only compatible with
<40 % organic solvent under
electrolytic conditions,
although can be up to 100 %
in chemical mode
 Packed-bed suppressors
tolerate much higher back
pressures than membrane
 Used in chemical mode and
compatible with 100 %
organic solvent
Membrane-based
Suppression

9. IC-MS Advantages: Sensitivity
Analyte
LOQ
IC-SCD
(ng)a*
LOQ
IC-HRMS
(pg)a*
Literature reported
IC-MS LOQ(pg)
Bromate – 190 2.3
Bromide – 51.9 93.3
Nitrate 0.3 400 4200
Chlorate – 35 1.5
Iodide – 18.2 33.3b
Thiocyanate 0.5 40.5 600
Perchlorate 1.2 8.2 0.7
a Signal-to-noise ratio of 10:1 for n = 6 low μg mL−1 standard runs
(20 μL loop).
b Pre-concentration step employed
SCD – suppressed conductivity detection; HRMS – high resolution
mass spectrometry.
S.K. Johnson et al. Analytica Chimica Acta 341 (1997), 205.
V.I. Furdui, F. Tomassini, Environmental Science & Technology 44
(2010), 588
A. Meyer et al. Journal of Chromatography A 1170 (2007), 62
B.C. Blount, L. Valentin-Blasini, Analytica Chimica Acta 567
(2006), 87
P.K. Martinelango et al. Analytica Chimica Acta 567 (2006), 100*Gilchrist et al. Analytica Chimica Acta, 865 (2015) 83-91

10. 0
5
10
15
20
25
30
0 2 4 6 8
Conductivity(μS/cm)
Time (min)
ClO3
-
Chlorate shown using CD and MS in SIM mode
No interference
Allows trace level analysis
2.0x107
1.0x107
0
0 2 4 6 8
Intensity
Time (min)
ClO3
-
m/z 83
IC-MS Advantages: Specificity

11. Coupling IC-MS: Solvent Addition
Injection Valve
Eluent
Reservoir
PUMP 1
Suppressor
Regenerant
Reservoir
Suppressor
PUMP 2
Volatile Solvent
Reservoir
Mixing Tee
PUMP 3
H2O or
Pre-Prepared eluent
(e.g. OH-)
H2O or
Chemical Regenerant
(e.g H2SO4)
MeCN, IPA,
MeOH
MS

12. -1
4
9
14
19
24
0 5 10 15 20 25 30 35
Conductivity(μS)
Time (min)
F-
Cl-
NO2
-
ClO3
- NO3
-
SO4
2-
PO4
3-
Column: IonPac AS19 (2 × 250 mm)
Eluent: OH- gradient
Suppressor: AERS 500
Electrolytic mode
Detection: SCD and ESI-TQ-MS
-ve mode
Solvent Addition
0
5000
10000
15000
20000
25000
30000
0 10 20 30 40
Intensity
Time (min)
Bromate
128.77->112.700
0
10000
20000
30000
40000
50000
60000
0 10 20 30 40
Intensity
Time (min)
Perchlorate
98.844->83.100

13. Coupling IC-MS: Direct Coupling
Injection Valve
Eluent
Reservoir
PUMP 1
Suppressor
Regenerant
Reservoir
Suppressor
PUMP 2
Pre-Prepared eluent
(e.g. OH-)
+ Volatile Solvent
H2O or
Chemical Regenerant
(e.g H2SO4)
MS

14. Column: IonPac AS18 (2 × 250 mm)
Eluent: 30 mM OH-, 35 % MeCN
Temperature: 35 oC
Flow rate: 0.18 mL/min
Suppressor: AMMS
Chemical mode
MS: ESI-Orbitrap-MS
-ve mode
100,000 FWHM
LOQs: 8.2 pg - 4.9 ng
2.0x107
1.0x107
0
0 5 10 15 20 25
Intensity
lactate
m/z 89.0245
2.0x107
1.0x107
0
0 5 10 15 20 25
Intensity
bromate
m/z 126.9033
2.0x107
1.0x107
0
0 5 10 15 20 25
Intensity
bromide
m/z 78.9187
7.5x106
5.0x106
2.5x106
0
0 5 10 15 20 25
Intensity
benzoate
m/z 121.0295
4.5x107
3.0x107
1.5x107
0
0 5 10 15 20 25
Intensity
nitrate
m/z 61.9885
4.0x107
2.0x107
0
0 5 10 15 20 25
Intensity
chlorate
m/z 82.9540
1.5x107
1.0x107
5.0x106
0
0 5 10 15 20 25
Intensity
oxalate
m/z 88.9878
2.0x107
1.0x107
0
0 5 10 15 20 25
Intensity
iodide
m/z 126.9050
1.5x107
1.0x107
5.0x106
0
0 5 10 15 20 25
Intensity
thiocyanate
m/z 57.9758
1.2x107
8.0x106
4.0x106
0
0 5 10 15 20 25
Intensity
phthalate
m/z 165.0193
1.5x107
7.5x106
0
0 5 10 15 20 25
Intensity
Retention Time (min)
perchlorate
m/z 98.9491
Direct Coupling
Gilchrist et al. Analytica Chimica Acta, 865 (2015) 83-91

15. 5x106
5x105
5x104
-10 10 30 50 70 90
Intensity
% MeCN
(a)
5x106
5x105
5x104
-10 10 30 50 70 90
Intensity
% MeOH
(b)
Optimised % Solvent for IC-MS
HRMS signal intensity with increasing solvent percentage for 0–
80 % (a) MeCN; or (b) MeOH via analyte direct infusion onto the
HRMS. [analyte]=5 μg/mL
thiocyanate
nitrate
oxalate
perchlorate
benzoate
phthalateGilchrist et al. Analytica Chimica Acta, 865 (2015) 83-91

16. Solvent Addition v Direct Coupling
Anion tR (min) tR %RSD Area %RSD tR (min) tR %RSD Area %RSD
Bromate 11.49 - - 7.74 0.25 11.00
Chlorate 16.08 0.05 6.56 8.47 0.19 8.00
Nitrate 18.83 0.04 6.42 8.04 0.23 15.00
Perchlorate 34.48 0.13 - 28.46 0.31 4.00
Solvent in eluentSolvent post suppressor

17. Summary
Already a variety of IC-MS technologies to select
from for a range of applications
 Advantages
 Sensitivity at trace level
 Specificity in complex matrices
 More information available on analytes
• Ability to speciate
• Structural elucidation

18. Acknowledgments
 Prof. Jeremy Glennon
 Dr. David Healy
 Dr. Virginia Morris
 Dr. Leon Barron
 Dr. Norman Smith
 Enterprise Ireland
 Sciex
 King’s Graduate School
Thank you

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