This document summarizes methods for analyzing oxyhalides using ion chromatography-mass spectrometry (IC-MS). It outlines considerations for coupling IC to MS, including flow rate compatibility and eluent volatility. Two main coupling methods are described: solvent addition, where an organic solvent is added post-column, and direct coupling, with organic solvent added pre-separation. Both methods are shown to achieve low detection limits in the picogram range for oxyhalides like bromate and perchlorate. Direct coupling provides better retention time reproducibility and precision compared to solvent addition. The document concludes by acknowledging contributions and providing information on submitting a poster abstract for a conference on the topic.
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
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
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